allways manifold vacuum on dis advance .....ported is a emmision thing ..... As many of you are aware, timing and vacuum advance is one of my favorite subjects, as I was involved in the development of some of those systems in my GM days and I understand it. Many people don't, as there has been very little written about it anywhere that makes sense, and as a result, a lot of folks are under the misunderstanding that vacuum advance somehow compromises performance. Nothing could be further from the truth. I finally sat down the other day and wrote up a primer on the subject, with the objective of helping more folks to understand vacuum advance and how it works together with initial timing and centrifugal advance to optimize all-around operation and performance. I have this as a Word document if anyone wants it sent to them - I've cut-and-pasted it here; it's long, but hopefully it's also informative. TIMING AND VACUUM ADVANCE 101 The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency. The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation. At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph). When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean. The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic. Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it. If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more. What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone. Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam. For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it - they don’t understand it, they're on commission, and they want to sell "race car" parts. __________________
one of my most prized possessions as was my snap on pressure gauge with about 4-5 in face from the fifties and so many different kinds if fittings its 420 legal so made a bowl and used them out of his tool box so i touch something he did all the time new every car from 30s-76 before i could multply and divide 😂 don't all kids in a diaper get to use impact wrench pulling transmissions apart Tony you could be my uncle as if you met my uncle you would think of him as a high school friend im 43 and hes like 20 older then me but they taught me everything i know was able to work on my single aunts car by 11 or 12 she allowed me to do it and she also knew how so she would allow me as she knows if he's able to build a gocart and its got spark plug too so i had my first customer and you don't charge family bring me the parts never leave stranded car was my oath people have came by in few minutes every time in 25 years if i was ever stopped and i know its because i didn't care i would be late to work and help someone then say i wish i had the time i remember helping woman with jump and ended up my boss's wife and i said remember how mad you are i helped your wife that may happen again im not going to do anything but make sure that they have phone if don't know how to start it and send help but not ever going to drive by and i was looking for job when i got this one so if you fire me at least i will be able to look myself in the mirror and sleep at night he said just call and he will send shop mechanic and just let them know and get to work so he offered and never had to send anyone and if i wouldn't have left it would have cost him more than 5 minutes of my time and he docked half hour and his wife said i do the payroll he just smiled i had my full 8hrs and my 1/2 for lunch i made up not knowing she was going to pay it 🙏 nothing wrong with helping people no reason to die not teaching people everything you know as the motors are outliving their owners h&h doing everything flatheads is cool don't let any of it die fix it till it breaks and then fix it again and and some compression but my bike is 36.6 cubic in 600rr honda makes 115hp@13,500 and bikes under 400 lbs it was previously stolen and i bought it that way but because honda made it in 03 so many things are the same and 1500$ runs 10s was my cheapest way to go fast now with today's situation keep head inside full face helmet walking in the store might be the law as im sure that would count as mask 👍
Uncle Tony, what’s the “screw”thats located just beneath the throttle, the one that can be backed in and out with a flat head? Ive been mistakenly adjusting that on my Scout II and id like to know what i was doing wrong now thati know what right looks like.
I have a 64 Chevy 2 5.7 sb I don’t have power brakes but do have hei distributor do I run my vacuum from carburetor to the vacuum advance on distributor or intake or does it matter. If this a dumb question sorry.
I feel the same way about my father. He’s been gone for 10 years., and he knew everything about carbureted engines , he could time a engine just by listening to it while he turned the distributor and get it right on the money
Your 30 second explanation of how to tune the springs in an Edelbrock helped me understand it better than I ever did reading the manual that came with it and watching a bunch of other videos. Thanks, Uncle Tony!
Ok, let me explain something about the ported vs manifold vacuum as it applies to distributor advance. If you have it hooked to manifold vacuum, it RETARDS the timing as soon as you touch the gas. The exact OPPOSITE of what you want to happen when the engine meets the initial load. Hooked to ported, it is inactive at idle as well as initial acceleration. Ported, it comes on when it is needed. Manifold, it turns off when the engine wants advance the most. Vacuum advance is intended for LIGHT throttle cruising, NOT acceleration. Make sense? I do not care which manufacturers used manifold vacuum, when they used it, or why. For best performance and to be used as originally intended, it should always be hooked to ported.
Tuning: manifold vacuum. Distributor: ported vacuum. Always. Got it. I have a question about when you actually had it running and tuning live. You were at 2 turns before it started. As soon as you started the engine you were at 16.5 for vacuum. At times it was higher. You finished it off at 16.5 again. Why? Why didn't you try to keep it at the higher vacuum signal? Please and thanks Unc'.
Tony, but isn't vacuum advance made for idle and cruise? As you say, once off idle, you want more ignition timing, but isn't that what centrifical advance is for...built into the distributor and sensitive to rpm? Kind of like three circuits for fuel delivery in a carburetor, a distributor needs initial advance (set at the crank), idle (vacuum advance routed to manifold), and wide-open throttle acceleration (centrifical), set by weights and springs in the distributor?
I agree that vacuum advance is for cruising & not acceleration, but I ALWAYS use manifold vacuum to the distributor, I have been tuning big blocks for nearly 40 years & found they always run better this way. Hook up a vacuum gauge to manifold & another to ported vacuum on the carb, route the hoses into the car & take it for a drive. At idle you have vacuum at manifold, none at port, at full throttle you have no vacuum from either, at cruising speed you have full manifold vacuum & ported vacuum varies on speed, but is less than manifold. The main advantages to using manifold vacuum is fuel economy. Set your timing & idle with vacuum disconnected as always, lets say your idle speed is 650rpms, then you plug vacuum hose back to vac advance & your idle speed jumps to lets say 8 or 900 rpms, too high, so you set idle back down to 650 with vac advance. This setting will use less fuel at idle & generally gives a smoother idle. The bigger savings is that when driving everytime your are coasting you are at this lower throttle setting & when you are cruising you are getting FULL vacuum advance too, so you maximize torque & mpg the same time, I have found this to give the average big block a 10% increase in economy, certain makes even more, especially Olds & Buicks.
You are absolutely incorrect about vacuum advance. It connects to manifold vacuum! At idle you have max vacuum which requires earlier firing of the lean mixture and causes the engine to run smoother. As the engine revs up from idle, the vacuum drops as does the vacuum advance, but the mechanical advance takes over! Now if you think I’m incorrect, which you do, get the book “Performance Ignitions and Tuning” written by Dr Christopher Jacobs. He has a PhD in electrical engineering and was the founder/owner of Jacobs Electronics which produced performance ignitions for years and MSD bought him out for millions of dollars when he took a lot of their market share. He used to consult to NASCAR and NHRA professional race teams when they had ignition problems. Dr Jacobs breaks it down in the book and no disrespect, but if you can’t top his credentials, which you can’t, then quit feeding people bad information that trust you.
this guy's a moron he don't know what he's talking about He's trying to act like he does because he's got a little bit of mechanical skill but he doesn't know what he's talking about I could tell you every emission part on anything from the '70s through the '97 OBD1 and I can do OBD2
And I'm watching him use a screwdriver on an Edelbrock performer carburetor use your fingers you can do it with one hand and hold the vacuum gauge with the other
I don't even use a vacuum gauge for that I'll set the static initial timing with a vacuum gauge you know when I see what the motor where it wants to run at an idle where the vacuum needs or the advance needs to be and then I'll set the advanced curve according to the camshaft and then I'll tune the carburetor by ear I don't need a vacuum gauge I can feel it and hear it you couldn't do any better with the vacuum gauge
Every old-skool car guy has a vacuum gauge and dwell/tach in the milk crate that's in the trunk. I don't actually know where the milk crates came from, I just know I always had a few, lying around. Maybe they grow in old car trunks.
Your right they do grow back there! I have one in my 67 Camaro with the timing light, dwell meter and vacuum guage along with cleaning supplies, all necessary tools to do about anything that might possible to wrong on a road trip! Bikers know what I'm referring to also!!! Need to watch out though because that coil of 16 or 18 guage wire you have in there for emergencies attracks mice which in return attracks snakes, like your common rat snake and black snakes!!! I kid you not, this actually occurs with the old 60s cars, they attract critters that love eating the insulation on the wiring from those years of cars! It happened to me! Had a mouse run up from the rear of the car after I started it and just ran out on my arm that I had laying on the door, you know like you leave your arm after adjusting your mirror, anyway he stopped at about my elbow and just started at me, must have been for 2-3 minutes we both just looked at each other, thought it was kinda cool at first then I thought about all the shorts he could cause, so I shook the heck out of my arm and he fell off to the garage floor and I took care of him, you know!!! Then later on that day was driving down the Interstate profiling in my gorgeous Quasar Blue 67 Camaro when I felt something kinda cold and moving up my bare leg due to wearing short pants that day and when I looked down saw a grayish looking snake with diamond makings on his back!! Needless to say this scared the crap out of me 😂 and I immediately switched lanes as physically possible over to the side of the road and immediately 😬 without any concern for safety, I mean I just had what I thought was a medium sized rattle snake slither up my naked leg for Christ sake, anyway I began trying to catch the little bastard with the work gloves I had found in the milk crate in the trunk, the 🐍 snake slithered into the heater vent on the driver's side of the console, that really was a bummer, was at a loss for a minute then decided to start the car back up and turn the heater on full blast, it worked the snake come hauling ass out of the hot vent, I saw he had no rattles on his tail and his head was not shaped like a poisonous 🐍 snake, whew gave me some relief, my BP returned to normal as did pulse and respiration, then the 🐍 slithered under the driver's seat, grabbed the largest screwdriver I could find from the milk crate and began chasing the huge fucker, he had miraculasly grown twice his original size, so here we go me head on the floor looking for the 🐍 snake, if he would have crawled toward me, that would have been it, ❤️ heart attack for sure! Luckily he didn't, he slithered under the back seat!! Oh boy, here I go tearing out the entire back seat of my precious 67 Quasar Blue Camaro on the side of the road on the Interstate! Got it all out 👍 faster than ever before because that 🐍 snake had slithered his way into the trunk and ended up in the milk crate!! I couldn't see him at all, he had hidden himself up under some shop rags! Now, by this time 2 other cars had stopped to see if I needed assistance, this happens when you ride a Harley and stop on the side of the Interstate or in a gorgeous classic car, folks just stop to see if there is anything at all they can help you with, just like in the old days!!! Anyway with my audience watching I was still nervously searching for the monster of a 🐍 snake, amazingly it just kept getting bigger and bigger all the time I was chasing it! With everyone looking on I picked up the milk crate and began to dump it in the trunk when the monster of a 🐍 snake came slithering out onto to trunk floor and curled himself around my left original tail light and at that time a guy about 18 I presume reached in, grabbed the monster 🐍 snake by the tail and uncurled him from around my 67 Camaro original tail light lifted him out of the trunk, showed him to all the concerned citizen s that had stopped to assist and explained it was a Rat 🐍 snake, he knew this because he was a Marine and had seen many snakes at Camp Lejeune and Paris Island so after holding it without any worries of being bit, he walked over to the edge of the forest on the side of the Interstate and ever so gently turned the little 🐍 snake loose into the woods! Now I know everyone is thinking how they would have felt with this situation so much different than I did, but until you have any kind of 🐍 snake crawl up your naked leg while your driving your gorgeous Quasar Blue 67 Camaro SS down the Interstate at 70 MPH you really can't say for sure exactly what your reactions would be!! I personally was so thankful for my milk crate that not only had everything I might have needed should my gorgeous Quasar Blue 67 Camaro SS might have broken down, not ever, but pays to always be prepared, just so happened I had everything required to Chase and capture extremely large snakes should the situation arrise!!! Just shows to go you how important that milk crate can be! So if you ever happen to see one at a yard sale, back of a old closed down grocery store, Craig's list or EBay, better but it, it could end up saving your life!! Really when you think about it, thousand wonders I did not wreak when I first looked down and saw that monster of a 🐍 snake crawling up my leg while driving my gorgeous Quasar Blue 67 Camaro SS down the Interstate! So just a little bit of advice 😉 place moth balls all around your garage to run the snakes off and I heard placing dryer sheets under your car seats and you can always store the box of sheets left over in your milk crate in your trunk! They are priceless!!! Hope you enjoyed my story, every bit of it was true!! Be safe out there and speed safely!!!GOD BLESS ALL AMERICANS!!!!
I’m a strong proponent of full manifold on vac advance. I’ve curved the distributor on my 396 to run this way and it’s a raped ape. Excellent fuel mileage too. Bone stock original 325 h p cam, 89,000 original miles. When set up properly you can achieve a strong running engine either way. Whatever works for your application, as I’ve seen it both ways over the years. Thanks for sharing your knowledge Tony. The vacuum gauge is one of those forgotten tools, but not for us old iron guys. Now break out your dwell meter and REALLY confuse the younger generation 😂
Manifold is genuinely pretty useless for a driver. You just leave efficiency on the table, although for something that sees zero vacuum more often than not, then the choice becomes irrelevant.
Anyone who actually takes the time to understand the air/fuel conditons of an engine at differing throttle positions, and loads, and the corrosponding timing requirements will understand why Manifold vac is the most useful method for a street driven engine. Ported vacuum can be made to work acceptably, but more initial timing is required, and economy, and street manners are sacraficed.
Manifold vacuum works the best. But if your using an hei distributor you need to limit the vacuum advances range to 10-12° of total movement. Similar to the vacuum advance range of a presmog points distributor which is usually 0-12° vacuum advance at full vacuum. Where a stock hei vacuum advance range can turn it 0-30degrees advance on some distributors.
Once again, the Man dispenses the gospel to the masses as simply as possible, therefore making it totally understandable and accessible even to the novices. This channel may be a lot of things, but the one that's always impressed me about Tony is how willing he is to share knowledge and help anyone who wants to know. BTW, this old goat just learned a new trick with that "checking the spring tension on the needle valve" bit on the Edelbrock. I've always just sort of stumbled my way along, using the infamous "chart" we all get with the AVS carbs as guidance until I hit on something that works. Tony's way saves a TON of time! Thanks as always, keep 'em calm over there in the flatlands neighbor, -Ed on the Ridge
Nice video with some good information. Here are some important clarifications: 1) vacuum should be checked with the air cleaner ON. Checking it without the air cleaner results in inaccurate readings, and your adjustments will be wrong. 2) Before adjusting the idle mixture screws, the engine timing at the distributor should be checked, and the idle speed should also be adjusted. Both of these come _before_ tuning the idle mixture screws with a vacuum gauge. 3) The engine should be HOT when checking vacuum. Uncle Tony started up the engine and immediately checked vacuum. I assume the engine had recently been running, but the point was never addressed. 4) The idle mixture screws should be turned in sequence, 1/4 turn on one, then 1/4 turn on the other. That way they're equal. If you adjust one screw for absolute maximum vacuum before adjusting the other screw, it's guaranteed that the screws won't be equally adjusted at the end of the process. And both screws should be equally adjusted.
You are a national treasure... Every old guy I meet tries their best to hold on to this information and then wonders why nobody want to use a carburetor and swaps everything to FI.
I'm a former Holley carb builder and tuner, and I moderate an engine group on facebook, I try to teach the younger generation about carbs, but I usually find that their minds are deadset against it because it's "old tech".
@@AmericanThunder When I was working on cars back in the nineties, I got all the electronic issues cause I was really good/fast at them (brakes too but that’s a different story). It caused me to not learn carbs like I should. No longer a mechanic by trade, but trying to learn the old stuff. While I can tune a fi system for performance, I can’t a carb yet. That just chaps me. Time to go old school
Did you ever here the definition of close enough for government work it is? You measure with a micrometer, mark it with a piece of chalk then cut it with a hatchet.
Thank you SO much! I was about to take the insurance off my 81 Malibu because I could not rid it of a off idle stumble!! Would stumble at cruising speed and for a moment when leaving a stop sign. Lost my pops to Covid last year and don’t know any old school guys that know their way around a small block. Went out after work with vacuum gauge after watching this video last night before bed. RUNS SO BADASS NOW!!! Driving it to work tomorrow
remember when JC Witney sold variable ignition timing kit so you could adjust your timing as you were driving. My first car was a 48 chevy. I tried the experiment of hooking the vacuum advance to the manifold vacuum. No, that did not work well at all. On my 48 chevy and the other old standard trans cars I had. one good way to adjust timing was this. with a hot engine and the gas you use(usually the cheapest regular). put the car in high gear at less than 20mph. step on the gas and as you accelerate it should ping a bit till you get to 30mph and then not ping there or above that. adjust the timing till you get that. now when you drive normally you get all the advance you can use because you do not normally lug the engine below 30 in high gear. you can cruse in high gear at 30 ok just not give it a lot of throttle. this would get the best gas mileage. Love your videos as you teach how this stuff is supposed to be done. if we just listen to the idle as we adjusted the mixture screw it will idle at max rpm if the idle mixture is rite. lots of stuff was done with no gages at all. do you need to have the vacuum advance working. Yes for mileage and no for power. since the vacuum advance is ported. if its not connected at all the idle is the same. also at full throttle there is very little vacuum that matters not much either. only daily drivers need the vacuum advance to work. when the vacuum advance is broken(or stuck) I would know because my mileage would drop off enough to know something was wrong.
we mounted on the dash where the radio had done been, a mallory mechanical advance box in my friends 69 roadrunner. That along with a T- valve that went from a reservoir of ATF to manifold vacuum. Hooked up a old choke push pull cable and let the show begin. A pull of the cable when driving, advance the timing and a smoke screen that James Bond would be envious of. Speaking of JC whitney we installed the exhaust cut outs they used to sell along with the lever that moved the pipe to one side on that same car. We were tired of dropping the pipes before racing at sears point every week , a few times before the cut outs we just drove home with open headers . The kit sucked and never sealed back up correctly but it was fun to open the exhaust while sitting at a light from inside the car, usually some kid talking about he was going to smoke us. The look on their faces was always the same as the exhaust sound changed and the cocky smirk went to, bewilderment and confusion, last the realization that something bad was about to happen. Those were good times!!!
I agree. I have a stock 77 Dodge Aspen with a 318 with 87,000 original miles and I hear a little puff puff every once in a while out the exhaust. The vacuum gage reading is lower than I expected (around 14ish) and bounces back and forth about ten inches of vacuum in that 14 inches range. The chart I looked at said bad valves. Hate to tear the engine down if it’s something else.
@@brucesherrill4116 Well, technically, just pulling the heads off is not an engine teardown. I've done that to a few engines, and sure I'd like to rebuild the whole thing, or at least hone and re-ring it. But you can only do what you can do sometimes. Especially under a shade tree in somebody else's driveway... You can fix that for the cost of head gaskets, intake gasket (which is almost optional) and a valve spring compressor. The screw on kind are not that much. After you've taken a wire brush and carburetor cleaner to the heads and made them shiny, stick a valve in, chuck the stem into your drill, and holding the valve tight in the seat with your other hand, spin and grind the shit out of it. You can get a decent valve job that way. Use plenty of grinding compound, and a slick oily rag will help keep your holding fingers from getting burned. Oil each guide first. Keep track of which valve went into which seat. Pulling against a drill will ruin it, you have to push with your other hand.
@@brucesherrill4116 I think AGG is talking about a lopey cam with little overlap at which point I would suggest running it rich, but lean enough doesn't load up if you don't drive it appropriately. However, replacing the valve seals on you 318 may reduce you erratic vacuum. If you have good and even compression, maybe burn a little oil, and the manifold gaskets are good, then worn valve guides and bad valve seals are likely the culprit. You can also tell if they are bad if you pull the valve cover and instead of the seals you see small pieces of plastic in you valve springs then they are gone.
These are the kind of tech videos I really like and get a lot of useful knowledge out of. I like knowing the "why and when" to something and not just how.
Mister Tony. I'm only 29 but I've played around with and drove classics since I was old enough to drive and before then some. If I would have had even a quarter of the knowledge you have on these carbureted engines when I was younger I probably woulda kept a lot of my old projects. Now that I'm getting back into it with a new project in the age of TH-cam and Google I've made it a mission to arm myself with actual facts and info about keeping these cars running and your videos have been the biggest help out of anything else I've watched. So thank you for sharing everything you know about old school cars with young bucks like me.
Ok i cant let Tony's comment go......it takes WAY more than 2 screws for government to work in fact at last count it took several dozen screws and a think 2-3 cans of lube spray....4 maybe see i'm screwed up now AAHHH!!!
There are other things that can be checked / inspected with a vacuum gauge, to include specific tune. ... Valve Timing ( Not to be confused with Ignition Timing ), Vacuum Signal ( From the Carb ) to the advance, which may also serve to ensure sufficient signal for vacuum controlled advance and the overall impact on vacuum if such advance controls are not only set properly, but, are not over advancing based on the signal produced. ... Even something as significant as a stretched timing chain can be identified by vacuum, or, at minimum narrowed as a probable cause of vacuum gauge movement / sweep. .... The vacuum gauge is a GREAT Tuning tool, as well as a GREAT Diagnostic tool. ... YES, I am OLD SCHOOL, I am also a ASE Certified Master Technician in BOTH Automotive ( Gas ) and OTR ( Diesel ). ... I also ran five ( 5 ) smog / Auto / Light Truck repair shops in Southern , California and A Performance Shop ( GM ONLY ) where I built custom performance engines, designed and sat up performance suspension systems and, on special cases, restored vehicles. .... I am not trying to bring my experience forward as a means to brag, instead, I bring it forward TO TEACH. ... Great Videos Man .... LET'S LEARN TOGETHER. .... Semper Fi
Hey Tony, Love your videos, and you obviously know your stuff. You do a great job! I have to disagree though with your suggestion of always using ported vacuum for the vacuum advance. An engine needs more advance at light load, and less timing under heavy load. Also, more timing under lean conditions, and less timing under rich conditions. I believe you have the history of ported/Manifold smog era schemes reversed. Looking at a 60's or earlier factory service manual, vacuum advance is always connected to manifold. Consider that the first thing you're always told to do when setting base timing is to disconnect the vacuum hose, and plug it. If it were going to a ported source, this would not be required, as there would be no vacuum at that port at idle. Sometime in the 70's most manufacturers move to ported vacuum, and distributors that were curved to take advantage of ported vac for better emissions. If your distributor is curved correctly... Manifold vacuum is the way to go for street performance.
I'm pro ported. I've done it both ways and in my experience the minimal fuel economy at idle along with zero performance or economy improvement at cruise or WOT isn't worth the trouble it causes with idle speed and starting in cold weather. Also I'd add that ignition 101 paper floating around way overstates the benefits of manifold vacuum. For example, If your car is overheating at idle and manifold vacuum is the difference then you have other problems.
Clelan Sametts it’s all the same except at idle and WOT (wot has no vacuum anyways so it’s a moot point). Manifold has timing advance at idle, lower EGT’s and not as good emissions, then pulls timing as the throttle blades are opened. Ported vacuum has no advance at idle, because it sees no vacuum at idle. As the throttle blades are opened, the vacuum rises and it adds timing advance. The way that you determine which is best is the way your distributor curve is set up, and your application. Some guys will swear by ported only, others by manifold only. If you have the ability to use a dyno I’m sure there’s a negligible difference in part throttle power, because in the middle of the part throttle operation, with the manifold vacuum advance dropping and the ported rising, they intersect at the same amount of advance. So, to sum it up, they achieve the same effect, just one adding timing and one taking timing out. The engine will run differently on each due to the way they add or remove timing. Remember, this is only idle and vacuum cruising, wide open throttle doesn’t matter for vacuum advance.
Joey Montemurro More advance at idle DOES NOT produce higher EGT, it lowers it. Other than that, you are spot on. Depends on how your particular distributor is curved.
do you mean when Chiltons Manuals were actually well written and the standard in most ROP and shop classes, back when a snap- on Calendars were printed for men by men with beautiful women with great bodies and happy to show it all tastefully. All the while showing off the tool of the month.
There is a lot of "grass roots" answers to how to set timing...most of em not correct but folks feel like it works for them. If it does, they just happen to stumble on the correct setting. You need to know two things on timing and the process becomes easy. 1) What is your target MAX timing for your engine - say in my case its 36 2) What is the all in advance of your distributor (not plugged to vacuum) which can be found by the manufacturer - usually at 2500-3000 rpms on up and done in crank degrees. so crank degrees of 10.5 = 21 cam timing advance (you multiply by 2). So if you want 36 max and it adds 21, subtract you get 14. So try it. Set it to 14 and you will , rev that engine..it sits nicely at 36...but don't exceed max because you can burn a piston or head gasket. I have seen guys where their advance is way off ...shooting 40 degrees max when it really should be 32 or 34. But like I said, you need TWO numbers. Setting till it pings and back off could still put you in danger zone. Not a good way to risk your engine
Totally agree Uncle Tony! That timing adjustment for maximum RPM never worked for me. Spark knock or pre-ignition (pinging) under load was an issue when done that way. I always set timing by taking it up a degree at a time and road test. When I heard spark knock I'd back it off one degree and be done. Of course I also knew that octane rating made a huge difference. I always tuned with fuel that was normally being used. Then for the hot rodders we could introduce things like water injection or methane to cool the combustion chamber and allow even more timing advance. Ahhhh -- the good old days!
Ah yes water injection can you buy them anymore I had a holly water injection system that I bought years ago my wife threw it out in the garbage I never did get to use it. My uncle was a great mechanic God Rest his soul and he told me about the water injection he said it increases the horsepower and it cleans the engine so you end up with the cleanest engine that you can ever have with no carbon in it
Back in the 70's I used basically a water fogger cause I couldn't afford a nitrous system. I would open the valve around 40 mph. It would lean the mixture out but nothing a little propane couldn't handle. Can't believe I never detonated an engine. Fun times!
@walterdowns9978 ok, before I say anything, I was a teenager in the 70's. Sporting a snorkel hood scoop, air shocks, traction bars, and a Predator carb, so not too bright. I drilled a short rise baseplate and put two mister/fogger nozzles and two threaded holes for propane. I had a small gas tank with an inline spark arrestor for the propane and a pressurized tank with water and opened both around 40mph. The water introduced an extra oxygen molecule (leaned it out) and took up space like nitrous to raise compression ratio (water doesn't compress) and the propane to help correct the lean issue. I've thought about doing it to my 77 El Camino, but maybe next weekend. Hope this helps or at least makes you go, what is wrong with that guy?
I would hesitate to say that only ported vacuum is used when it's a direct connection between the carb and distributor, or that only 70's era cars used manifold vacuum. My advice would be to try it both ways and see how your car reacts. Personally, my 67 289 Mustang runs much nicer with manifold vacuum, which is how it was hooked up when I bought it in 1977. The throttle response, idle, and mileage are noticeably better. Try it both ways.
My 66 396 has 4 inches of vacuum at idle and vacuum advance removed from the HEI. Holley Dbl pumper and enrichment valve plugged and jetted up. TH400 trans reprogrammed to work without vacuum modulator. Manual brakes. Only thing I set by vacuum in mixture. Lol
We used to diagnose blocked exhaust with a vacuum gauge. As you raise the engine speed above idle, manifold vacuum should increase. If it doesn't, check your exhaust.
Also , a bouncy, erractic gauge, is an indication of weak , or broken valve spring(s) . Also use em to make sure that the modulator line to trans has adequate vaccum, not ported vaccum.
But a good number of GM cars used manifold vacuum for the vacuum advance well before emissions came into play. It tends to give a smoother idle. Once you are off idle, it operates just like an engine with ported vacuum. It is only there for part throttle economy, advancing the timing as far a possible when load is light.
Back in the 1960's GM big blocks, if the engine wasn't worn out, factory timing almost always gave you nearly the best vacuum. I always used a light, but confirmed with the vacuum gauge for fine tweaks. Now to be honest... that didn't always give you the best smog settings. Back in 1981 I took my 1966 Olds (425 4bbl) through State inspection running really well. It literally set a new station record for worst pollution ever recorded on their analog instruments. It was so bad that they stopped the inspection line and let me re-tune the engine while hooked up to the machine. After a lot of fast tweaks the car passed for 1981 pollution standards... but man it ran like crap. On the up side, it did get better gas mileage. So keep in mind... best vacuum doesn't always mean best pollution... nor best gas mileage. And yes, I know it should, but it doesn't... Also, with the vacuum gauge, you can tweak an engine to run best on different octane fuels. By 1981, it was getting hard to get Sunoco 260, 100 octane which my engine was originally tuned for.
@@moparnut6286 I'm in NJ and it was at the Livingston inspection station... in the drive in theater... that My Olds was being inspected. When they stuffed the tester into the tail pipe... pandemonium broke out among the workers who all rushed over to see the highest readings ever recorded on the old analog gauges... "I can fix it" I told them while they pointed and cracked jokes... So I got my tools out of the trunk... while the line of cars behind me backed up onto Rt 10 and I adjusted the idle screws, and the timing and made other adjustments while the guys watched the meters for improvement... and made recommendations... like take off the air cleaner, pull the PCV, turn up the idle, etc. It was rather bazaar, but I was grateful because I didn't have a pollution meter which at the time cost thousands of dollars to work with. Finally the guy at the machine says, that's as good as it's going to get. And when I asked if I passed... He said, you passed for 1966 5 minutes ago... you actually passed for 1981. (which was actually a catalytically converted standard and my car had no such converter) In any case, I had to do several adjustments to get the car running well enough to drive home after that. Buy yes... My 66 Olds, 73 Buick, 84 Plymouth, 92 and 94 Saturns don't need inspection in NJ and all but the 94 Saturn are either tagged antiques or on collector insurance. Unfortunately, I've got to find the dang evap leak by next year to pass inspection for my 02 Ford.... I truly hate new cars.
@@RJ-vb7gh That was very decent of the inspection station to allow you to adjust while hooked up to their meter. Here in Oregon we bet they would not allow it.
@@frederickbooth7970My car failed so spectacularly that the entire inspection staff came over to see the machine readings... They said they didn't even know the machine could read so high. By that point everyone working there was invested in seeing how low the emissions could be tweaked down to, while they made suggestions. When I asked if I passed the guy said, "You passed 10 minutes ago for a 66, but now you pass for a brand new car. (circa 1982)" That's pretty much when I realized that all of the smog stuff and the catalytic converter didn't do much of anything on a car that was tuned properly. If your engine is burning clean... there's not much for the smog stuff to do. To be fair... once tweaked to ace emissions, the car ran poorly, I had to undo a couple tweaks to drive the car home. In the end doable wasn't optimal. But no... that wasn't the inspection station extending me a courtesy, it was more like them exercising their curiosity. Pretty much any car with with a carburetor and and an independent ignition system can be tweaked to pass pretty much any smog test if it isn't smoking. And if it's smoking... you bring it through after dark in winter when the inspection station is open late... I had to do inspection 5 times until it got dark early enough for me to pass another car. And even smoking... it passed the machine test, just no one noticed the smoke.
All of my vehicles from the 1950's through the 1980's used manifold vacuum for vacuum advance, requiring the vac line be disconnected from the advance can and plugged off (I always used a golf tee) to check and set ignition timing. Some heavily emsioned vehicles (mainly 1974-ish through the early 80's California emission) used ported vacuum to reduce HC at idle or used a valve that delayed vacuum to the distributor like an OSAC valve (Chrysler version), sometimes using both methods (most of these engines were complete dogs and obtained horrible fuel mileage). Modified engines with hotter cams sometimes required ported vacuum, depending on the setup. This was usually a crutch though. The best method was to us an adjustable vacuum advance can and tune it, after the distributor weight springs were properly selected. Full out race engines back in the day didn't use vacuum advance and generally locked out the centrifugal weights in the distributor. In the 1980's, dual diaphragm vacuum advance cans became the norm for most vehicles which used both ported and manifold vacuum, providing much more precise control for timing in all ranges of operation. My 1984 Toyota pickup uses one of these and requires the manifold vac line be removed and plugged to check and adjust timing (5 degrees BTDC). Something I learned rather quickly in my younger days using a vacuum gauge to adjust fuel mixtures is that it'll get it in the ballpark range, but using a sensitive RPM tach with a large display (I use a 1970's Sears model) will get the fuel mixtures adjusted much more precisely. I have had to use a vacuum gauge to adjust timing on stock engines which had 2 piece harmonic balancers that slipped as age and miles accumulated. The worst offender was a slant 6. The balancer slipped more than 25 degrees, and living at 30 feet above sea level, I'd adjust for 20" of vacuum after the carb was tuned, recheck fuel mixture adjustment again, then recheck timing. Of course, everything else needs to be in perfect working order to be successful: Ignition system needs to be up to par, zero vacuum leaks, tappets in good working order (if hydraulic) and valves properly adjusted (if mechanical).
Manifold vacuum advance on any good high compression engine always obtain the best results for me ported vacuum just doesn’t make any sense especially with a slightly bigger cam shaft
Most car companies all were using manifold vacuum, about 1968 they started using ported vacuum due to emissions and better gas mileage. By 1970 onward they all were using ported vacuum. Only full time race cars would be using centrifugal advance or locked out. For a street car, use a ported vacuum in all cases, even in a "lopey" camshaft because at idle there is no vacuum at all.
@@jeffkellner1585 same here enem with a slightly modified 350. Mild cam and I added a 1.6 exhaust valve into my ported world products heads. I have never used ported. I tried but I couldn't get the idle where I wanted it to be. Numerous vehicles too, not just one engine. If engines died every day from full manifold vacuum people wouldn't use it. I also limited my vacuum advance to 8 degrees. Initial was 12. Total was at 34. Replying Jeff, yes this is an old one but it's always bugged me too. Maybe Mopars respond better that way.
Lol! I have a vacuum gauge from the late 80’s . Vacuum gauge great for tuning and diagnostics . I use to have to do it at the rest areas . When driving thru the mountains.
60s buicks use a thermoswitch to switch between manifold and ported vacuum based on temperature. This allows full manifold vacuum at cold start and then switches to ported vacuum once warmed up. It also has a trick that when the car returns to idle it switches to manifold vacuum for better idle. All of this is done with thermosensor in the manifold... pretty neat and should be no problem to add to any old carbureted car with an extra temperature sender sized hole available.
on holley with power valve and 1/2 mercury between manifold vacuum on power valve vacuum reading. do u put one vacuum on manifold and and one on carb port and look for differential until it is at closest 1/2 way point? and do u use idle mixture screws to set it? thanks, forgive me i'm learning. i just rebuilt my 2100 2 barrel on a 289. works great but i wanna learn more
Yeeeep almost 60. 43yrs trade life, I watch a fella tune carbys and listen to them. Makes me sick knowing how much he charges for what he gives them. I did a 383 chev on Friday. Has a 411 Edelbrock on it. It flys now. The man who owns it, has owned it for well over 30yrs, and swears blind it has never gone so well. Swears blind it has never fired up istantly from dead cold. Maybe I am made different not sure. I admit I had to go look up how edelbrock carbs work, because It's so long since last I tuned one. Thank You Tony for your imformation refresher course😊
You can blame the engineers for changing all this, including amount of electronics that run the vehicle compared to older cars. Not a bad thing for new technicians like myself. I just started 5-6 years ago. Just more things we need to learn on top of all the modern technology. I always love a challenge to learn. If only we can go back to these days🤣
Please stop spreading misinformation about how to connect ignition vacuum advance. Please do some level of research before just irresponsibly posting videos. The "ported" connection is used for emissions vehicles configurations, and even then somewhere in the mid to late 1970's they smartened up and started using "trapped spark ignition" instead, which is the complicated stuff you gleamed on briefly in the video but clearly did not understand. The only reason why they ever used ported signal for vacuum advance at all is because emissions go through the roof when you use a lot of vacuum advance at idle. So they decided to go with ported advance, and then use an A.I.R. system to burn the leftover hydrocarbons in the hot exhaust that were not burned off, otherwise other emissions types from unspent hydrocarbons were present. They eventually had to work around the other problems experienced with ported signal for vacuum advance by then later introducing the trapped spark ignition because it would run like total crap when cold. Also, not enough vacuum advance at idle will make the car run hot in traffic and piss through more gas. By telling people to only use ported vacuum for the spark advance, you are selling an idea that was used for complying with emissions standards in 1970's, without the benefit of the rest of the system. If your car is running better with ported signal instead of manifold signal for vacuum spark advance, then great. You probably have other things somewhat misconfigured that as a result make this appear to be the best way to go for you. My suggestion to you is to take your distributor to someone who has a Sun machine and have it recurved properly, so you don't have to pull in so much base timing advance to compensate. You would be surprised how out of wack those things can get when they are old and worn. Heck, I bought a brand new HEI unit and found that the springs were far too heavy for my application. If I were less informed, I would have just bumped up the base timing to make it run better, then realize that the ported vacuum works better for my application. Assuming that you have too much base spark timing advance, I can see why using ported for vacuum advance appears to make the car run better.
For more precise setting, always adjust curb idle speed and basic timing before adjusting carburator. It is advised to use a tachometer in conjunction with the vacuum gauge for the entire process.
Thanks, just bought an 84Chevy (350 with an Edelbrock), it ran decent on the long drive back. I pulled the plugs and they're black(mostly) and grey. I will follow your advice.
On a holley 2210 rebuilt the idle air screw on driver's side make no change... passenger side screw shows immediate change...what could be the issue with driver's side. I see no videos on idle air screw issues and what could be it's problem when no adjustment to idle is notice when turning one...any thoughts?
I was thinking at first you could kind of tell he was legit by the way he was holding his cigarette….but once he said “was that right, well it’s close enough for government work” I knew he was.
The reason you use ported vacuum to the distribution. At idle the throttle blades are closed no vacuumed as you open the throttle blades you pull more vacuumed advance. So at cruising speeds you can pull more advance . But when you floor it the vacuum drops and the vacuum advance drops off preventing detonation. You can always pull more advance at low load on the engine cruising speeds.
Incomplete. You did not show where to plug the guage in. What about people who have never done this before? You can't use a vacuum gauge if dot dont know where to plug the darn thing up at. My carb only has one port. It's where the vaccum advance goes. the other carb port has no pressure in any direction, thus. it always stays at 0. There is no where to plug a vaccum guage up on my 350 (that I can find) Only a larger "T" plug into the manifold on the backside of the carb. . and if there was a place I would not know which one to use. I like your videos, but where are places you plug up a vaccum guage. Please use a finger to point to a few specific places please. Many people that have this type issue don't even respond, only the people who have several ports and can do this respond.
If you seriously cant just look at the video and trace the rubber hose..... when its obviously doing a close up at one of the parts... Do you even need to try to tune your own engine? Probably not. Let your wife do it. 😂
Vacume gage will diagnose a restricted exhaust plugged cationic converter bad baffles in a muffler. At idle full ported vacume snap the throttle instantly the vacuum gage should go to close to zero no delay or no wanting to change instantly means a restricted exhaust.
back in the day my dad had JC Whitney vacuum gauges on all the cars for max MPG. The '70 VW Squareback with fuel injection and the '74 Pinto 4 spd were always neck and neck for best mileage.
IA 2001 Chevy S10 4.3 V6 fuel injectin have you ever heard of doing plugs wires and cap you have to reprogram the computer please comment back I know somebody who got theirs done and their mechanic raced their vehicle so much this stuff from the catalytic converter was coming out the exhaust day more or Lass blew up this person's motor Am I right or wrong please comment back in let me know if you know thank you
Only thing I ever needed for a vacum gage was for the holley power valve. If you still have a good ear you can tune just by the sound. A tack will help get the best idle but when you snap the throttle you most likely need to turn the idle screws out a 1/4 to half turn more out. This works with a stock cam or a little more of a cam. Big cams forget most that stuff. There is pump shot and a whole a lot of stuff that comes into play here. I have to use a electric vacum pump plus a vacum can so my power breaks will work. At idle with my cam idle at 1200 rpm I only get around 8 inches. Why I have a 3.5 or 2.5 power valve in both blocks on my 850 holley on a 454BBC. With MSD I don't even use a vacum dist. When am at full throttle my vacum is near zero. If I drive long distance I get 12 miles to a gallon. Around town maybe 3 or 5 miles per gallon. Power cost. A good video for a newbie though.
On anything without an ECU I advance the initial timing to the point where I can take off in 2nd uphill and not get pinging. If I have a timing light and want to set up the whole curve, I start Ford's and Chevy's around 30 to 32 total advance and mopars at 34. I then drive it and adjust the advance plates to feel, and again under load, with no pinging.
i’m 38 my dads like this guy we have a machine shop still building race cars... carbureted still... i remember in the 80’s we had a oldmobile station wagon, it had a “fuel economy” gauge in the cluster i said how’s that work? he said vacuum and he smashed the gas it pegged over then came full back to the (+) side and he explained how it worked the more vacuum, the more the butterfly’s are closed the less fuel the more open the less vacuum and worse fuel idk why but i thought that was the coolest thing
Total ignition advance is basic timing you set by turning the distributor mechanical advance springs weights in the distributor and vacuumed advance add all 3 together you get total ignition timing advance
@@UncleTonysGarage That's an argument I can't find a answer to. My 67 Pontiac Tempest uses manifold vacuum from the factory. I've tried setting it up ported and it runs better on manifold.
Gm cars used manifold vacuum up until the 70’s when they switched to ported to raise exhaust temps to help burn off more emissions. I had a 1968 327 in a truck that always ran hot when set up with ported vacuum. Switched to manifold and temps came down and off idle power was way up.
As far as manifold goes there's really little use to having your vacuum advance all at once off idle. Ported makes sense because the advance comes in while at cruising speed, so your timing would ultimately be in the beneficial 45ish range at cruising.
My dad was trained as a mechanic. He did all of his maintenance and most engine repairs. He always tuned an engine with just a vacuum gauge, no timing light. He taught me a lot but I always had to use a timing light because I couldn’t get it right with a vacuum gauge. That cars I tuned were a 70 AMC Gremlin 232, 70 AMC Ambassador 360 and a 78 Honda Civic CVCC. After that, things got to complicated for me with all the electronics involved. This video brought back fond memories of all my dad taught me.
THANK YOU! for covering this and answering questions I had from the last video. Plus I look forward to seeing Bottle Rocket and the slant 6 Dart run. I'm curious to see what kind of numbers they run. You and Uncle Cathy keep up the great work! 😁
I’ve always set my timing by manifold vacuum, with the vacuum advance disconnected, and backed off by 5 inches of mercury to account for ignition advance under acceleration and higher RPM. With a performance engine, I found that I had to back off the timing just a tad more to keep it from detonating, pinging and make it easier to start, but it usually isn’t by very much. Setting timing with the timing light was never really an option for me because the engines that I had used aftermarket camshaft, various different compression ratios and everything else was pretty much is thrown together so I really couldn’t set timing with a timing light according to any recommendation.
And that's why you set timing to total and let initial fall where it will. If more initial is needed, time to curve the distributor and narrow the advance range.
@@UncleTonysGarage If you have a large cam you can also use your manifold vacuum for the vacuum advance. If will pull that idle timing forward a bit for a smoother idle in a large cam situation. On stock engines they used ported vacuum because the advance would be too far at idle and you would be making NO based emissions they didn't like. When you have a low vacuum from a big cam the manifold vacuum and a very quick short advance curve helps a lot.
Hi UT! I have a billet distributor no vacuum advance. Where/what do I hook up my vacuum guage to? Holley 4160 750 cfm double pumper with vacuum secondaries. Thank you Uncle Tony.
This comment of mine is old and I now understand what to do. My new Holley came with a "timed port" for Vac Advance I see. Mine is now plugged and my vac gauge was plugged into the manifold port. Tuning this was a breeze and highly recommended alond with UT timing tips. Thanks UT!
Took me 64 years to find someone who knew what they were talking about,……and could (between spitting, shaking and thinking faster than any Ferrari mechanic,) teach me in four point something minutes, the most valuable, take it anywhere, knowledge that you can get! I don’t care what you wear, Tony, you just gained a believer!!!
I like how my '98 Ford 4.2 runs stuff with vacuum. The '03 4.2 that I got out of the yard had electronic IMRC controls. I just had to use my '98 upper intake, harness, fuel injectors and IMRC actuators on the '03 block, lower intake and heads. Had to do surgery to relocate the knock sensor though. And switch around a couple sensors. And use the '98 EGR and heater tube. Got the battery tray in today. First start maybe tomorrow. Can anyone recommend good explosion insurance?
Each hash is one inch. He started with it bouncing between 16.5 and 17. He ended with it solid at 17 inches. Zero is towards clockwise, more vacuum is counterclockwise on that gauge.
I love this channel. So many cool nuggets of information and tips. I'm a big 80s-90s euro guy, but I did own a 74 "Gold" 318 Duster for about a year. Was too young, an inexperienced to properly rebuild it so I sold it. Eight years later after watching much of this channel, I'm getting excited to give it a try once again.
When I was young I would always set my timing with a vacuum gauge. I'd increase timing by advancing the distributor for maximum vacuum and when the vacuum started to fall off I would reduce it by 1 inch of mercury. I would then recheck the timing with my timing light. worked for me!
It would take a couple hours to explain all the tuning points on a holley carb lol. I tried breaking it up into different videos on the channel and Im still not done! Good work uncle tony!
Hey I hope to hear back from you, I’m stumped. I have a stock 350 sbc with low miles. It is a GM crate engine. The issue I’m having is the engine is bogging out over 3000 rpm’s. Things I’ve done chasing this issue, new distributior, new plugs and wires, set timing at 14 initial, replaced mechanical fuel pump, replaced fuel filter, replaced fuel tank sock, replaced all rubber hoses, made sure gas tank is venting properly, replaced air filter, and rebuilt carburetor. I’m honestly baffled and worried it might be an internal problem. Also I removed the fuel pump push rod and stuck my bore-scope camera in the hole and had a buddy bump the engine over to inspect the cam lob to make sure it wasn’t flat. Everything checks out fine. The carb I am using is a Holley 1450 with vacuum secondaries, it is an old carb that I’ve rebuilt before. Also plugs look great, doesn’t appear to be to lean/rich. And the timing looks mint on the ground strap. Could it be a burnt valve? Or is the old flat tappet cam giving up? Idk, hope to hear back from you.
i found this video very helpful. I am new to carbureted vehicles because i was born well after fuel injection came out. I recently picked up a 1968 El Camino SS with a 396 Big Block and have been getting acclimated. Thanks for putting out this content. It is very straightforward and helpful.
Uncle Tony, talk about perfect timing for this video! I'll be taking an extensive road trip soon with an old carb engine and was looking to do a solid tune on my Weber carb before I head out. I had been planning on doing some research on this but haven't done anything yet. I purchased a vacuum gauge from china freight the other day and was hoping to get this done sometime during this week. Wouldn't you know it, you uploaded a video that answered all the questions I had and explained it thoroughly for a rookie like myself who's hoping to keep the carb alive! I really appreciate this video and can't wait to dive into this form of fine tuning myself soon! I'm also gonna be using this method to help my friend fine tune his carb on a 5.0 mustang from an engine swap we recently did on it. Really appreciate your videos! They're definitely better than enough for government work. Hahah. I appreciate your videos and thanks for what you do!
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allways manifold vacuum on dis advance .....ported is a emmision thing .....
As many of you are aware, timing and vacuum advance is one of my favorite subjects, as I was involved in the development of some of those systems in my GM days and I understand it. Many people don't, as there has been very little written about it anywhere that makes sense, and as a result, a lot of folks are under the misunderstanding that vacuum advance somehow compromises performance. Nothing could be further from the truth. I finally sat down the other day and wrote up a primer on the subject, with the objective of helping more folks to understand vacuum advance and how it works together with initial timing and centrifugal advance to optimize all-around operation and performance. I have this as a Word document if anyone wants it sent to them - I've cut-and-pasted it here; it's long, but hopefully it's also informative.
TIMING AND VACUUM ADVANCE 101
The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency.
The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation.
At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph).
When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean.
The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic.
Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.
If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.
What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.
Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.
For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it - they don’t understand it, they're on commission, and they want to sell "race car" parts.
__________________
I read this a few years ago, made sense then, and still does today. Thanks for your efforts.
Thanks! Make perfect sense.
Thanks!
as a beginner and a DIY, how can say where is my manifold vacuum on my carb?
@@zombeesama1169
Manifoiol vacuum is below the throttle blades.
Ported vacuum is over throttle blades.
Another fine piece of work, well explained and easy to understand for anyone.
Thats how I LEARNED back in the day! Thanks to you!
Nice explanation. You always teach me something new.
Good like always.
I have used a vacuum gage to check on valve, lifter, rocker arm problems. A Carter AFB and Strip Kit make life so much easier.
one of my most prized possessions as was my snap on pressure gauge with about 4-5 in face from the fifties and so many different kinds if fittings its 420 legal so made a bowl and used them out of his tool box so i touch something he did all the time new every car from 30s-76 before i could multply and divide 😂 don't all kids in a diaper get to use impact wrench pulling transmissions apart Tony you could be my uncle as if you met my uncle you would think of him as a high school friend im 43 and hes like 20 older then me but they taught me everything i know was able to work on my single aunts car by 11 or 12 she allowed me to do it and she also knew how so she would allow me as she knows if he's able to build a gocart and its got spark plug too so i had my first customer and you don't charge family bring me the parts never leave stranded car was my oath people have came by in few minutes every time in 25 years if i was ever stopped and i know its because i didn't care i would be late to work and help someone then say i wish i had the time i remember helping woman with jump and ended up my boss's wife and i said remember how mad you are i helped your wife that may happen again im not going to do anything but make sure that they have phone if don't know how to start it and send help but not ever going to drive by and i was looking for job when i got this one so if you fire me at least i will be able to look myself in the mirror and sleep at night he said just call and he will send shop mechanic and just let them know and get to work so he offered and never had to send anyone and if i wouldn't have left it would have cost him more than 5 minutes of my time and he docked half hour and his wife said i do the payroll he just smiled i had my full 8hrs and my 1/2 for lunch i made up not knowing she was going to pay it 🙏 nothing wrong with helping people no reason to die not teaching people everything you know as the motors are outliving their owners h&h doing everything flatheads is cool don't let any of it die fix it till it breaks and then fix it again and and some compression but my bike is 36.6 cubic in 600rr honda makes 115hp@13,500 and bikes under 400 lbs it was previously stolen and i bought it that way but because honda made it in 03 so many things are the same and 1500$ runs 10s was my cheapest way to go fast now with today's situation keep head inside full face helmet walking in the store might be the law as im sure that would count as mask 👍
Ported and venture vac is different too .... but I agree ported.. the amount of advance at the distributor is sometimes adjustable.
My favorite part of this video is the spider webs!
Manifold vacuum got the automakers through the beginning of emissions standards. They used vacuum to control everything.
Uncle Tony, what’s the “screw”thats located just beneath the throttle, the one that can be backed in and out with a flat head? Ive been mistakenly adjusting that on my Scout II and id like to know what i was doing wrong now thati know what right looks like.
Hello, my problem is 7,000 ft elevation , where I live , Vacuum Gauge, always say's 9 no mater what or where I put it.
Uncle Tony's Garage help! I'm pulling my hair out with an avs 2 thunder series carb!
I can do that!!
I love this channel.
I have a 64 Chevy 2 5.7 sb I don’t have power brakes but do have hei distributor do I run my vacuum from carburetor to the vacuum advance on distributor or intake or does it matter. If this a dumb question sorry.
like it that you are not scared to lay stuff on the fender....tho I think that cigarette should have been lit!
Is the guage connected to the advance port on the carb?
If I close my eyes I can hear my dad talking cars, and car maintenance. I wish I would have listened a lot closer to my dad. Uncle Tony you rock.
I feel the same way about my father. He’s been gone for 10 years., and he knew everything about carbureted engines , he could time a engine just by listening to it while he turned the distributor and get it right on the money
Your 30 second explanation of how to tune the springs in an Edelbrock helped me understand it better than I ever did reading the manual that came with it and watching a bunch of other videos. Thanks, Uncle Tony!
👍
Reading that Edelbrock manual caused man to want to drink
Ok, let me explain something about the ported vs manifold vacuum as it applies to distributor advance.
If you have it hooked to manifold vacuum, it RETARDS the timing as soon as you touch the gas. The exact OPPOSITE of what you want to happen when the engine meets the initial load.
Hooked to ported, it is inactive at idle as well as initial acceleration. Ported, it comes on when it is needed. Manifold, it turns off when the engine wants advance the most.
Vacuum advance is intended for LIGHT throttle cruising, NOT acceleration.
Make sense?
I do not care which manufacturers used manifold vacuum, when they used it, or why. For best performance and to be used as originally intended, it should always be hooked to ported.
Tuning: manifold vacuum.
Distributor: ported vacuum.
Always. Got it.
I have a question about when you actually had it running and tuning live.
You were at 2 turns before it started.
As soon as you started the engine you were at 16.5 for vacuum.
At times it was higher.
You finished it off at 16.5 again.
Why? Why didn't you try to keep it at the higher vacuum signal?
Please and thanks Unc'.
Tony, but isn't vacuum advance made for idle and cruise? As you say, once off idle, you want more ignition timing, but isn't that what centrifical advance is for...built into the distributor and sensitive to rpm? Kind of like three circuits for fuel delivery in a carburetor, a distributor needs initial advance (set at the crank), idle (vacuum advance routed to manifold), and wide-open throttle acceleration (centrifical), set by weights and springs in the distributor?
I agree that vacuum advance is for cruising & not acceleration, but I ALWAYS use manifold vacuum to the distributor, I have been tuning big blocks for nearly 40 years & found they always run better this way. Hook up a vacuum gauge to manifold & another to ported vacuum on the carb, route the hoses into the car & take it for a drive. At idle you have vacuum at manifold, none at port, at full throttle you have no vacuum from either, at cruising speed you have full manifold vacuum & ported vacuum varies on speed, but is less than manifold. The main advantages to using manifold vacuum is fuel economy. Set your timing & idle with vacuum disconnected as always, lets say your idle speed is 650rpms, then you plug vacuum hose back to vac advance & your idle speed jumps to lets say 8 or 900 rpms, too high, so you set idle back down to 650 with vac advance. This setting will use less fuel at idle & generally gives a smoother idle. The bigger savings is that when driving everytime your are coasting you are at this lower throttle setting & when you are cruising you are getting FULL vacuum advance too, so you maximize torque & mpg the same time, I have found this to give the average big block a 10% increase in economy, certain makes even more, especially Olds & Buicks.
You are absolutely incorrect about vacuum advance. It connects to manifold vacuum! At idle you have max vacuum which requires earlier firing of the lean mixture and causes the engine to run smoother. As the engine revs up from idle, the vacuum drops as does the vacuum advance, but the mechanical advance takes over! Now if you think I’m incorrect, which you do, get the book “Performance Ignitions and Tuning” written by Dr Christopher Jacobs. He has a PhD in electrical engineering and was the founder/owner of Jacobs Electronics which produced performance ignitions for years and MSD bought him out for millions of dollars when he took a lot of their market share. He used to consult to NASCAR and NHRA professional race teams when they had ignition problems. Dr Jacobs breaks it down in the book and no disrespect, but if you can’t top his credentials, which you can’t, then quit feeding people bad information that trust you.
@@trailerparkcryptoking5213 he also said the 440 has a small cam which makes less vacuum . also wrong .
This is the stuff that people need. Knowing this is the difference between being a guy, and being a man
Thank you very much
The lost art that many mechanics never had.
Boy, you got that right! ! !
My Dad .had a great ability to do that ..
this guy's a moron he don't know what he's talking about He's trying to act like he does because he's got a little bit of mechanical skill but he doesn't know what he's talking about I could tell you every emission part on anything from the '70s through the '97 OBD1 and I can do OBD2
And I'm watching him use a screwdriver on an Edelbrock performer carburetor use your fingers you can do it with one hand and hold the vacuum gauge with the other
I don't even use a vacuum gauge for that I'll set the static initial timing with a vacuum gauge you know when I see what the motor where it wants to run at an idle where the vacuum needs or the advance needs to be and then I'll set the advanced curve according to the camshaft and then I'll tune the carburetor by ear I don't need a vacuum gauge I can feel it and hear it you couldn't do any better with the vacuum gauge
Every old-skool car guy has a vacuum gauge and dwell/tach in the milk crate that's in the trunk. I don't actually know where the milk crates came from, I just know I always had a few, lying around. Maybe they grow in old car trunks.
Have you noticed the coffee cans are popping up plastic now?
@@nickmcwilliams685 yeah, mixed feelings about it. I'm sure I have a Chock full O'Nuts can rusting here someplace...
Mr. Blutarsky they come from under old dirt bikes
@@deborahchesser7375 that must be it!
Your right they do grow back there! I have one in my 67 Camaro with the timing light, dwell meter and vacuum guage along with cleaning supplies, all necessary tools to do about anything that might possible to wrong on a road trip! Bikers know what I'm referring to also!!! Need to watch out though because that coil of 16 or 18 guage wire you have in there for emergencies attracks mice which in return attracks snakes, like your common rat snake and black snakes!!! I kid you not, this actually occurs with the old 60s cars, they attract critters that love eating the insulation on the wiring from those years of cars! It happened to me! Had a mouse run up from the rear of the car after I started it and just ran out on my arm that I had laying on the door, you know like you leave your arm after adjusting your mirror, anyway he stopped at about my elbow and just started at me, must have been for 2-3 minutes we both just looked at each other, thought it was kinda cool at first then I thought about all the shorts he could cause, so I shook the heck out of my arm and he fell off to the garage floor and I took care of him, you know!!! Then later on that day was driving down the Interstate profiling in my gorgeous Quasar Blue 67 Camaro when I felt something kinda cold and moving up my bare leg due to wearing short pants that day and when I looked down saw a grayish looking snake with diamond makings on his back!! Needless to say this scared the crap out of me 😂 and I immediately switched lanes as physically possible over to the side of the road and immediately 😬 without any concern for safety, I mean I just had what I thought was a medium sized rattle snake slither up my naked leg for Christ sake, anyway I began trying to catch the little bastard with the work gloves I had found in the milk crate in the trunk, the 🐍 snake slithered into the heater vent on the driver's side of the console, that really was a bummer, was at a loss for a minute then decided to start the car back up and turn the heater on full blast, it worked the snake come hauling ass out of the hot vent, I saw he had no rattles on his tail and his head was not shaped like a poisonous 🐍 snake, whew gave me some relief, my BP returned to normal as did pulse and respiration, then the 🐍 slithered under the driver's seat, grabbed the largest screwdriver I could find from the milk crate and began chasing the huge fucker, he had miraculasly grown twice his original size, so here we go me head on the floor looking for the 🐍 snake, if he would have crawled toward me, that would have been it, ❤️ heart attack for sure! Luckily he didn't, he slithered under the back seat!! Oh boy, here I go tearing out the entire back seat of my precious 67 Quasar Blue Camaro on the side of the road on the Interstate! Got it all out 👍 faster than ever before because that 🐍 snake had slithered his way into the trunk and ended up in the milk crate!! I couldn't see him at all, he had hidden himself up under some shop rags! Now, by this time 2 other cars had stopped to see if I needed assistance, this happens when you ride a Harley and stop on the side of the Interstate or in a gorgeous classic car, folks just stop to see if there is anything at all they can help you with, just like in the old days!!! Anyway with my audience watching I was still nervously searching for the monster of a 🐍 snake, amazingly it just kept getting bigger and bigger all the time I was chasing it! With everyone looking on I picked up the milk crate and began to dump it in the trunk when the monster of a 🐍 snake came slithering out onto to trunk floor and curled himself around my left original tail light and at that time a guy about 18 I presume reached in, grabbed the monster 🐍 snake by the tail and uncurled him from around my 67 Camaro original tail light lifted him out of the trunk, showed him to all the concerned citizen s that had stopped to assist and explained it was a Rat 🐍 snake, he knew this because he was a Marine and had seen many snakes at Camp Lejeune and Paris Island so after holding it without any worries of being bit, he walked over to the edge of the forest on the side of the Interstate and ever so gently turned the little 🐍 snake loose into the woods! Now I know everyone is thinking how they would have felt with this situation so much different than I did, but until you have any kind of 🐍 snake crawl up your naked leg while your driving your gorgeous Quasar Blue 67 Camaro SS down the Interstate at 70 MPH you really can't say for sure exactly what your reactions would be!! I personally was so thankful for my milk crate that not only had everything I might have needed should my gorgeous Quasar Blue 67 Camaro SS might have broken down, not ever, but pays to always be prepared, just so happened I had everything required to Chase and capture extremely large snakes should the situation arrise!!! Just shows to go you how important that milk crate can be! So if you ever happen to see one at a yard sale, back of a old closed down grocery store, Craig's list or EBay, better but it, it could end up saving your life!! Really when you think about it, thousand wonders I did not wreak when I first looked down and saw that monster of a 🐍 snake crawling up my leg while driving my gorgeous Quasar Blue 67 Camaro SS down the Interstate! So just a little bit of advice 😉 place moth balls all around your garage to run the snakes off and I heard placing dryer sheets under your car seats and you can always store the box of sheets left over in your milk crate in your trunk! They are priceless!!! Hope you enjoyed my story, every bit of it was true!! Be safe out there and speed safely!!!GOD BLESS ALL AMERICANS!!!!
I’m a strong proponent of full manifold on vac advance. I’ve curved the distributor on my 396 to run this way and it’s a raped ape. Excellent fuel mileage too. Bone stock original 325 h p cam, 89,000 original miles. When set up properly you can achieve a strong running engine either way. Whatever works for your application, as I’ve seen it both ways over the years. Thanks for sharing your knowledge Tony. The vacuum gauge is one of those forgotten tools, but not for us old iron guys. Now break out your dwell meter and REALLY confuse the younger generation 😂
Manifold is genuinely pretty useless for a driver. You just leave efficiency on the table, although for something that sees zero vacuum more often than not, then the choice becomes irrelevant.
asus6983 Read the link I posted. It will prove that wrong.
Anyone who actually takes the time to understand the air/fuel conditons of an engine at differing throttle positions, and loads, and the corrosponding timing requirements will understand why Manifold vac is the most useful method for a street driven engine. Ported vacuum can be made to work acceptably, but more initial timing is required, and economy, and street manners are sacraficed.
Manifold vacuum works the best. But if your using an hei distributor you need to limit the vacuum advances range to 10-12° of total movement. Similar to the vacuum advance range of a presmog points distributor which is usually 0-12° vacuum advance at full vacuum.
Where a stock hei vacuum advance range can turn it 0-30degrees advance on some distributors.
Modern turbo builds and younger guys use vacuum readings more than you realize. “Old iron” doesn’t matter, vac matters on all builds.
Refreshing to see old some school tuning again, no laptops required, thanks to uncle Tony.
Once again, the Man dispenses the gospel to the masses as simply as possible, therefore making
it totally understandable and accessible even to the novices.
This channel may be a lot of things, but the one that's always impressed me about Tony is how
willing he is to share knowledge and help anyone who wants to know.
BTW, this old goat just learned a new trick with that "checking the spring tension on the needle valve"
bit on the Edelbrock. I've always just sort of stumbled my way along, using the infamous "chart"
we all get with the AVS carbs as guidance until I hit on something that works.
Tony's way saves a TON of time!
Thanks as always, keep 'em calm over there in the flatlands neighbor,
-Ed on the Ridge
Nice video with some good information. Here are some important clarifications:
1) vacuum should be checked with the air cleaner ON. Checking it without the air cleaner results in inaccurate readings, and your adjustments will be wrong.
2) Before adjusting the idle mixture screws, the engine timing at the distributor should be checked, and the idle speed should also be adjusted. Both of these come _before_ tuning the idle mixture screws with a vacuum gauge.
3) The engine should be HOT when checking vacuum. Uncle Tony started up the engine and immediately checked vacuum. I assume the engine had recently been running, but the point was never addressed.
4) The idle mixture screws should be turned in sequence, 1/4 turn on one, then 1/4 turn on the other. That way they're equal. If you adjust one screw for absolute maximum vacuum before adjusting the other screw, it's guaranteed that the screws won't be equally adjusted at the end of the process. And both screws should be equally adjusted.
For your #3 go back and listen about 8:25 mark
You are a national treasure... Every old guy I meet tries their best to hold on to this information and then wonders why nobody want to use a carburetor and swaps everything to FI.
I'm a former Holley carb builder and tuner, and I moderate an engine group on facebook, I try to teach the younger generation about carbs, but I usually find that their minds are deadset against it because it's "old tech".
@@AmericanThunder When I was working on cars back in the nineties, I got all the electronic issues cause I was really good/fast at them (brakes too but that’s a different story). It caused me to not learn carbs like I should. No longer a mechanic by trade, but trying to learn the old stuff. While I can tune a fi system for performance, I can’t a carb yet. That just chaps me. Time to go old school
Cracked me up at 'close enough for government work'
Funny stuff indeed! It's an old school quip going back to the 1940's.
Did you ever here the definition of close enough for government work it is? You measure with a micrometer, mark it with a piece of chalk then cut it with a hatchet.
@@briansd2772 maybe even before to the 30s when a lot of people were working in government programs like WPA.
@@johnbecay6887 Yep. It had a positive meaning originally.
Thank you SO much! I was about to take the insurance off my 81 Malibu because I could not rid it of a off idle stumble!! Would stumble at cruising speed and for a moment when leaving a stop sign. Lost my pops to Covid last year and don’t know any old school guys that know their way around a small block. Went out after work with vacuum gauge after watching this video last night before bed. RUNS SO BADASS NOW!!! Driving it to work tomorrow
remember when JC Witney sold variable ignition timing kit so you could adjust your timing as you were driving. My first car was a 48 chevy. I tried the experiment of hooking the vacuum advance to the manifold vacuum. No, that did not work well at all. On my 48 chevy and the other old standard trans cars I had. one good way to adjust timing was this. with a hot engine and the gas you use(usually the cheapest regular). put the car in high gear at less than 20mph. step on the gas and as you accelerate it should ping a bit till you get to 30mph and then not ping there or above that. adjust the timing till you get that. now when you drive normally you get all the advance you can use because you do not normally lug the engine below 30 in high gear. you can cruse in high gear at 30 ok just not give it a lot of throttle. this would get the best gas mileage. Love your videos as you teach how this stuff is supposed to be done. if we just listen to the idle as we adjusted the mixture screw it will idle at max rpm if the idle mixture is rite. lots of stuff was done with no gages at all. do you need to have the vacuum advance working. Yes for mileage and no for power. since the vacuum advance is ported. if its not connected at all the idle is the same. also at full throttle there is very little vacuum that matters not much either. only daily drivers need the vacuum advance to work. when the vacuum advance is broken(or stuck) I would know because my mileage would drop off enough to know something was wrong.
I think that was the MSD Ping Control.
we mounted on the dash where the radio had done been, a mallory mechanical advance box in my friends 69 roadrunner. That along with a T- valve that went from a reservoir of ATF to manifold vacuum. Hooked up a old choke push pull cable and let the show begin. A pull of the cable when driving, advance the timing and a smoke screen that James Bond would be envious of. Speaking of JC whitney we installed the exhaust cut outs they used to sell along with the lever that moved the pipe to one side on that same car. We were tired of dropping the pipes before racing at sears point every week , a few times before the cut outs we just drove home with open headers . The kit sucked and never sealed back up correctly but it was fun to open the exhaust while sitting at a light from inside the car, usually some kid talking about he was going to smoke us. The look on their faces was always the same as the exhaust sound changed and the cocky smirk went to, bewilderment and confusion, last the realization that something bad was about to happen. Those were good times!!!
Oh wow, I actually discovered this on my own when I just started working on my car in the mid 2000s. It just made a lot of sense to me.
GO AWAY,your reminding me how old I am!
I had the MSD variable timing control in my 1993 mustang. Not sure it did much, would turn it up a few degrees at the track, back down for cruising
.Dont crush that joint with your elbow .
should do a demonstration on erratic vacuum readings and valve lash
I agree. I have a stock 77 Dodge Aspen with a 318 with 87,000 original miles and I hear a little puff puff every once in a while out the exhaust.
The vacuum gage reading is lower than I expected (around 14ish) and bounces back and forth about ten inches of vacuum in that 14 inches range. The chart I looked at said bad valves.
Hate to tear the engine down if it’s something else.
@@brucesherrill4116 Well, technically, just pulling the heads off is not an engine teardown. I've done that to a few engines, and sure I'd like to rebuild the whole thing, or at least hone and re-ring it. But you can only do what you can do sometimes. Especially under a shade tree in somebody else's driveway...
You can fix that for the cost of head gaskets, intake gasket (which is almost optional) and a valve spring compressor. The screw on kind are not that much. After you've taken a wire brush and carburetor cleaner to the heads and made them shiny, stick a valve in, chuck the stem into your drill, and holding the valve tight in the seat with your other hand, spin and grind the shit out of it. You can get a decent valve job that way. Use plenty of grinding compound, and a slick oily rag will help keep your holding fingers from getting burned. Oil each guide first. Keep track of which valve went into which seat. Pulling against a drill will ruin it, you have to push with your other hand.
@@brucesherrill4116 I think AGG is talking about a lopey cam with little overlap at which point I would suggest running it rich, but lean enough doesn't load up if you don't drive it appropriately.
However, replacing the valve seals on you 318 may reduce you erratic vacuum. If you have good and even compression, maybe burn a little oil, and the manifold gaskets are good, then worn valve guides and bad valve seals are likely the culprit. You can also tell if they are bad if you pull the valve cover and instead of the seals you see small pieces of plastic in you valve springs then they are gone.
It means it usually means your guides are worn, or if you have solid lifters you have them set wrong.
These are the kind of tech videos I really like and get a lot of useful knowledge out of. I like knowing the "why and when" to something and not just how.
Thank you Tony 16 lbs manifold vacuum. Set carb screws. You have been a great teacher for me... I appreciate it thank you. Sir... Ryan
Mister Tony. I'm only 29 but I've played around with and drove classics since I was old enough to drive and before then some. If I would have had even a quarter of the knowledge you have on these carbureted engines when I was younger I probably woulda kept a lot of my old projects. Now that I'm getting back into it with a new project in the age of TH-cam and Google I've made it a mission to arm myself with actual facts and info about keeping these cars running and your videos have been the biggest help out of anything else I've watched. So thank you for sharing everything you know about old school cars with young bucks like me.
Another good channel is Muscle Car Solutions. Uncle Tony knows mopars and I'm a mopar guy
Your level of knowledge is impressive.
Ok i cant let Tony's comment go......it takes WAY more than 2 screws for government to work in fact at last count it took several dozen screws and a think 2-3 cans of lube spray....4 maybe see i'm screwed up now AAHHH!!!
You forgot that if those were 2 government screws they probably cost about $3567 a piece depending on shipping , for mild steel.
Those would be defined as screwballs
@@MrTheHillfolk and still not work correctly
@@jamesbetts3371 you have to install it upside down , probably.
Lol
"Fine Engine Tuning" - of course it's a fine engine - it's a Mopar.
There are other things that can be checked / inspected with a vacuum gauge, to include specific tune. ... Valve Timing ( Not to be confused with Ignition Timing ), Vacuum Signal ( From the Carb ) to the advance, which may also serve to ensure sufficient signal for vacuum controlled advance and the overall impact on vacuum if such advance controls are not only set properly, but, are not over advancing based on the signal produced. ... Even something as significant as a stretched timing chain can be identified by vacuum, or, at minimum narrowed as a probable cause of vacuum gauge movement / sweep. .... The vacuum gauge is a GREAT Tuning tool, as well as a GREAT Diagnostic tool. ... YES, I am OLD SCHOOL, I am also a ASE Certified Master Technician in BOTH Automotive ( Gas ) and OTR ( Diesel ). ... I also ran five ( 5 ) smog / Auto / Light Truck repair shops in Southern , California and A Performance Shop ( GM ONLY ) where I built custom performance engines, designed and sat up performance suspension systems and, on special cases, restored vehicles. .... I am not trying to bring my experience forward as a means to brag, instead, I bring it forward TO TEACH. ... Great Videos Man .... LET'S LEARN TOGETHER. .... Semper Fi
Hey Tony, Love your videos, and you obviously know your stuff. You do a great job! I have to disagree though with your suggestion of always using ported vacuum for the vacuum advance. An engine needs more advance at light load, and less timing under heavy load. Also, more timing under lean conditions, and less timing under rich conditions. I believe you have the history of ported/Manifold smog era schemes reversed. Looking at a 60's or earlier factory service manual, vacuum advance is always connected to manifold. Consider that the first thing you're always told to do when setting base timing is to disconnect the vacuum hose, and plug it. If it were going to a ported source, this would not be required, as there would be no vacuum at that port at idle. Sometime in the 70's most manufacturers move to ported vacuum, and distributors that were curved to take advantage of ported vac for better emissions. If your distributor is curved correctly... Manifold vacuum is the way to go for street performance.
Correct, the "always ported" vac is bollox, all my BB Mopars have run full vac for over 35 years with no detonation.
Totally agree!!
I'm pro ported. I've done it both ways and in my experience the minimal fuel economy at idle along with zero performance or economy improvement at cruise or WOT isn't worth the trouble it causes with idle speed and starting in cold weather. Also I'd add that ignition 101 paper floating around way overstates the benefits of manifold vacuum. For example, If your car is overheating at idle and manifold vacuum is the difference then you have other problems.
I'd like to hear more about ported vacuum VS manifold vacuum on the vacuum advance.
Clelan Sametts it’s all the same except at idle and WOT (wot has no vacuum anyways so it’s a moot point). Manifold has timing advance at idle, lower EGT’s and not as good emissions, then pulls timing as the throttle blades are opened. Ported vacuum has no advance at idle, because it sees no vacuum at idle. As the throttle blades are opened, the vacuum rises and it adds timing advance. The way that you determine which is best is the way your distributor curve is set up, and your application. Some guys will swear by ported only, others by manifold only. If you have the ability to use a dyno I’m sure there’s a negligible difference in part throttle power, because in the middle of the part throttle operation, with the manifold vacuum advance dropping and the ported rising, they intersect at the same amount of advance. So, to sum it up, they achieve the same effect, just one adding timing and one taking timing out. The engine will run differently on each due to the way they add or remove timing. Remember, this is only idle and vacuum cruising, wide open throttle doesn’t matter for vacuum advance.
Check out Thunderhead289, he practically has a PHD in manifold and ported vacuum.
@@Ltmonte Joey. You should have a more thumbs up best answer I've seen it really is your distributor curve that seems to make the difference.
Joey Montemurro More advance at idle DOES NOT produce higher EGT, it lowers it. Other than that, you are spot on. Depends on how your particular distributor is curved.
Let the ARGUMENTS START!!!!!!
This used to be standard information in the repair manuals back in the day.
do you mean when Chiltons Manuals were actually well written and the standard in most ROP and shop classes, back when a snap- on Calendars were printed for men by men with beautiful women with great bodies and happy to show it all tastefully. All the while showing off the tool of the month.
There is a lot of "grass roots" answers to how to set timing...most of em not correct but folks feel like it works for them. If it does, they just happen to stumble on the correct setting. You need to know two things on timing and the process becomes easy. 1) What is your target MAX timing for your engine - say in my case its 36 2) What is the all in advance of your distributor (not plugged to vacuum) which can be found by the manufacturer - usually at 2500-3000 rpms on up and done in crank degrees. so crank degrees of 10.5 = 21 cam timing advance (you multiply by 2). So if you want 36 max and it adds 21, subtract you get 14. So try it. Set it to 14 and you will , rev that engine..it sits nicely at 36...but don't exceed max because you can burn a piston or head gasket. I have seen guys where their advance is way off ...shooting 40 degrees max when it really should be 32 or 34. But like I said, you need TWO numbers. Setting till it pings and back off could still put you in danger zone. Not a good way to risk your engine
Totally agree Uncle Tony! That timing adjustment for maximum RPM never worked for me. Spark knock or pre-ignition (pinging) under load was an issue when done that way. I always set timing by taking it up a degree at a time and road test. When I heard spark knock I'd back it off one degree and be done. Of course I also knew that octane rating made a huge difference. I always tuned with fuel that was normally being used. Then for the hot rodders we could introduce things like water injection or methane to cool the combustion chamber and allow even more timing advance. Ahhhh -- the good old days!
Ah yes water injection can you buy them anymore I had a holly water injection system that I bought years ago my wife threw it out in the garbage I never did get to use it. My uncle was a great mechanic God Rest his soul and he told me about the water injection he said it increases the horsepower and it cleans the engine so you end up with the cleanest engine that you can ever have with no carbon in it
to adjust timing with a vacuum gauge, find highest vacuum then back off 2 inches. this is the best timing
@@walterdowns9978 check out snow performance. Mostly diesel applications but they sell a simple kit
Back in the 70's I used basically a water fogger cause I couldn't afford a nitrous system. I would open the valve around 40 mph. It would lean the mixture out but nothing a little propane couldn't handle.
Can't believe I never detonated an engine. Fun times!
@walterdowns9978 ok, before I say anything, I was a teenager in the 70's. Sporting a snorkel hood scoop, air shocks, traction bars, and a Predator carb, so not too bright.
I drilled a short rise baseplate and put two mister/fogger nozzles and two threaded holes for propane. I had a small gas tank with an inline spark arrestor for the propane and a pressurized tank with water and opened both around 40mph.
The water introduced an extra oxygen molecule (leaned it out) and took up space like nitrous to raise compression ratio (water doesn't compress) and the propane to help correct the lean issue.
I've thought about doing it to my 77 El Camino, but maybe next weekend.
Hope this helps or at least makes you go, what is wrong with that guy?
I would hesitate to say that only ported vacuum is used when it's a direct connection between the carb and distributor, or that only 70's era cars used manifold vacuum. My advice would be to try it both ways and see how your car reacts. Personally, my 67 289 Mustang runs much nicer with manifold vacuum, which is how it was hooked up when I bought it in 1977. The throttle response, idle, and mileage are noticeably better. Try it both ways.
Uncle Tony can you vacuum tune the government? my taxes are too high
You want to increase the vacuum in your bank account? 😆😂
Such attempts are usually overwhelmed by the prodigious supply of hot air. ;)
My 66 396 has 4 inches of vacuum at idle and vacuum advance removed from the HEI. Holley Dbl pumper and enrichment valve plugged and jetted up. TH400 trans reprogrammed to work without vacuum modulator. Manual brakes. Only thing I set by vacuum in mixture. Lol
We used to diagnose blocked exhaust with a vacuum gauge. As you raise the engine speed above idle, manifold vacuum should increase. If it doesn't, check your exhaust.
Also , a bouncy, erractic gauge, is an indication of weak , or broken valve spring(s) . Also use em to make sure that the modulator line to trans has adequate vaccum, not ported vaccum.
But a good number of GM cars used manifold vacuum for the vacuum advance well before emissions came into play. It tends to give a smoother idle. Once you are off idle, it operates just like an engine with ported vacuum. It is only there for part throttle economy, advancing the timing as far a possible when load is light.
Back in the 1960's GM big blocks, if the engine wasn't worn out, factory timing almost always gave you nearly the best vacuum. I always used a light, but confirmed with the vacuum gauge for fine tweaks.
Now to be honest... that didn't always give you the best smog settings. Back in 1981 I took my 1966 Olds (425 4bbl) through State inspection running really well. It literally set a new station record for worst pollution ever recorded on their analog instruments. It was so bad that they stopped the inspection line and let me re-tune the engine while hooked up to the machine. After a lot of fast tweaks the car passed for 1981 pollution standards... but man it ran like crap. On the up side, it did get better gas mileage.
So keep in mind... best vacuum doesn't always mean best pollution... nor best gas mileage. And yes, I know it should, but it doesn't...
Also, with the vacuum gauge, you can tweak an engine to run best on different octane fuels. By 1981, it was getting hard to get Sunoco 260, 100 octane which my engine was originally tuned for.
@@moparnut6286 I'm in NJ and it was at the Livingston inspection station... in the drive in theater... that My Olds was being inspected. When they stuffed the tester into the tail pipe... pandemonium broke out among the workers who all rushed over to see the highest readings ever recorded on the old analog gauges...
"I can fix it" I told them while they pointed and cracked jokes... So I got my tools out of the trunk... while the line of cars behind me backed up onto Rt 10 and I adjusted the idle screws, and the timing and made other adjustments while the guys watched the meters for improvement... and made recommendations... like take off the air cleaner, pull the PCV, turn up the idle, etc. It was rather bazaar, but I was grateful because I didn't have a pollution meter which at the time cost thousands of dollars to work with.
Finally the guy at the machine says, that's as good as it's going to get. And when I asked if I passed... He said, you passed for 1966 5 minutes ago... you actually passed for 1981. (which was actually a catalytically converted standard and my car had no such converter)
In any case, I had to do several adjustments to get the car running well enough to drive home after that.
Buy yes... My 66 Olds, 73 Buick, 84 Plymouth, 92 and 94 Saturns don't need inspection in NJ and all but the 94 Saturn are either tagged antiques or on collector insurance. Unfortunately, I've got to find the dang evap leak by next year to pass inspection for my 02 Ford.... I truly hate new cars.
@@RJ-vb7gh That was very decent of the inspection station to allow you to adjust while hooked up to their meter. Here in Oregon we bet they would not allow it.
@@frederickbooth7970My car failed so spectacularly that the entire inspection staff came over to see the machine readings... They said they didn't even know the machine could read so high. By that point everyone working there was invested in seeing how low the emissions could be tweaked down to, while they made suggestions. When I asked if I passed the guy said, "You passed 10 minutes ago for a 66, but now you pass for a brand new car. (circa 1982)"
That's pretty much when I realized that all of the smog stuff and the catalytic converter didn't do much of anything on a car that was tuned properly. If your engine is burning clean... there's not much for the smog stuff to do. To be fair... once tweaked to ace emissions, the car ran poorly, I had to undo a couple tweaks to drive the car home. In the end doable wasn't optimal.
But no... that wasn't the inspection station extending me a courtesy, it was more like them exercising their curiosity. Pretty much any car with with a carburetor and and an independent ignition system can be tweaked to pass pretty much any smog test if it isn't smoking. And if it's smoking... you bring it through after dark in winter when the inspection station is open late... I had to do inspection 5 times until it got dark early enough for me to pass another car. And even smoking... it passed the machine test, just no one noticed the smoke.
In the 70’s and 80’s the engineers would throw spaghetti at the engine. Wherever they landed on the engine they would hook up vacuum lines.
And then in '91 Ford came out with the new Escort that had exactly 1 vacuum line. I was like holy crap I have to buy this car.
Isnt this just general knowledge they teached like in high school shop or am i just that old 😳
Shop has been gone since about 95 where I was. The kids knew more than the instructor in my class. He hated me!
All of my vehicles from the 1950's through the 1980's used manifold vacuum for vacuum advance, requiring the vac line be disconnected from the advance can and plugged off (I always used a golf tee) to check and set ignition timing. Some heavily emsioned vehicles (mainly 1974-ish through the early 80's California emission) used ported vacuum to reduce HC at idle or used a valve that delayed vacuum to the distributor like an OSAC valve (Chrysler version), sometimes using both methods (most of these engines were complete dogs and obtained horrible fuel mileage). Modified engines with hotter cams sometimes required ported vacuum, depending on the setup. This was usually a crutch though. The best method was to us an adjustable vacuum advance can and tune it, after the distributor weight springs were properly selected. Full out race engines back in the day didn't use vacuum advance and generally locked out the centrifugal weights in the distributor.
In the 1980's, dual diaphragm vacuum advance cans became the norm for most vehicles which used both ported and manifold vacuum, providing much more precise control for timing in all ranges of operation. My 1984 Toyota pickup uses one of these and requires the manifold vac line be removed and plugged to check and adjust timing (5 degrees BTDC).
Something I learned rather quickly in my younger days using a vacuum gauge to adjust fuel mixtures is that it'll get it in the ballpark range, but using a sensitive RPM tach with a large display (I use a 1970's Sears model) will get the fuel mixtures adjusted much more precisely.
I have had to use a vacuum gauge to adjust timing on stock engines which had 2 piece harmonic balancers that slipped as age and miles accumulated. The worst offender was a slant 6. The balancer slipped more than 25 degrees, and living at 30 feet above sea level, I'd adjust for 20" of vacuum after the carb was tuned, recheck fuel mixture adjustment again, then recheck timing. Of course, everything else needs to be in perfect working order to be successful: Ignition system needs to be up to par, zero vacuum leaks, tappets in good working order (if hydraulic) and valves properly adjusted (if mechanical).
Manifold vacuum advance on any good high compression engine always obtain the best results for me ported vacuum just doesn’t make any sense especially with a slightly bigger cam shaft
Most car companies all were using manifold vacuum, about 1968 they started using ported vacuum due to emissions and better gas mileage. By 1970 onward they all were using ported vacuum. Only full time race cars would be using centrifugal advance or locked out. For a street car, use a ported vacuum in all cases, even in a "lopey" camshaft because at idle there is no vacuum at all.
@@jeffkellner1585 same here enem with a slightly modified 350. Mild cam and I added a 1.6 exhaust valve into my ported world products heads. I have never used ported. I tried but I couldn't get the idle where I wanted it to be. Numerous vehicles too, not just one engine.
If engines died every day from full manifold vacuum people wouldn't use it. I also limited my vacuum advance to 8 degrees. Initial was 12. Total was at 34.
Replying Jeff, yes this is an old one but it's always bugged me too. Maybe Mopars respond better that way.
Lol! I have a vacuum gauge from the late 80’s . Vacuum gauge great for tuning and diagnostics . I use to have to do it at the rest areas . When driving thru the mountains.
I use full manifold vacuum for my '68 L36 Vette and '65 4-4-2 for the distributor vacuum cannister. Ported is for later, smogger cars.
60s buicks use a thermoswitch to switch between manifold and ported vacuum based on temperature. This allows full manifold vacuum at cold start and then switches to ported vacuum once warmed up. It also has a trick that when the car returns to idle it switches to manifold vacuum for better idle. All of this is done with thermosensor in the manifold... pretty neat and should be no problem to add to any old carbureted car with an extra temperature sender sized hole available.
on holley with power valve and 1/2 mercury between manifold vacuum on power valve vacuum reading. do u put one vacuum on manifold and and one on carb port and look for differential until it is at closest 1/2 way point? and do u use idle mixture screws to set it?
thanks, forgive me i'm learning. i just rebuilt my 2100 2 barrel on a 289. works great but i wanna learn more
Today's mechanics don't know what a carburetor is. Much less a timing light. Not a bad thing, just showing how old we really are. ✌
It's definitely a bad thing. Lol
Yeeeep almost 60. 43yrs trade life, I watch a fella tune carbys and listen to them.
Makes me sick knowing how much he charges for what he gives them.
I did a 383 chev on Friday. Has a 411 Edelbrock on it.
It flys now.
The man who owns it, has owned it for well over 30yrs, and swears blind it has never gone so well. Swears blind it has never fired up istantly from dead cold.
Maybe I am made different not sure.
I admit I had to go look up how edelbrock carbs work, because It's so long since last I tuned one. Thank You Tony for your imformation refresher course😊
You can blame the engineers for changing all this, including amount of electronics that run the vehicle compared to older cars. Not a bad thing for new technicians like myself. I just started 5-6 years ago. Just more things we need to learn on top of all the modern technology. I always love a challenge to learn. If only we can go back to these days🤣
@@smokeysmishaps4214government regulations created all this lol
Please stop spreading misinformation about how to connect ignition vacuum advance. Please do some level of research before just irresponsibly posting videos. The "ported" connection is used for emissions vehicles configurations, and even then somewhere in the mid to late 1970's they smartened up and started using "trapped spark ignition" instead, which is the complicated stuff you gleamed on briefly in the video but clearly did not understand. The only reason why they ever used ported signal for vacuum advance at all is because emissions go through the roof when you use a lot of vacuum advance at idle. So they decided to go with ported advance, and then use an A.I.R. system to burn the leftover hydrocarbons in the hot exhaust that were not burned off, otherwise other emissions types from unspent hydrocarbons were present. They eventually had to work around the other problems experienced with ported signal for vacuum advance by then later introducing the trapped spark ignition because it would run like total crap when cold. Also, not enough vacuum advance at idle will make the car run hot in traffic and piss through more gas. By telling people to only use ported vacuum for the spark advance, you are selling an idea that was used for complying with emissions standards in 1970's, without the benefit of the rest of the system. If your car is running better with ported signal instead of manifold signal for vacuum spark advance, then great. You probably have other things somewhat misconfigured that as a result make this appear to be the best way to go for you. My suggestion to you is to take your distributor to someone who has a Sun machine and have it recurved properly, so you don't have to pull in so much base timing advance to compensate. You would be surprised how out of wack those things can get when they are old and worn. Heck, I bought a brand new HEI unit and found that the springs were far too heavy for my application. If I were less informed, I would have just bumped up the base timing to make it run better, then realize that the ported vacuum works better for my application. Assuming that you have too much base spark timing advance, I can see why using ported for vacuum advance appears to make the car run better.
For more precise setting, always adjust curb idle speed and basic timing before adjusting carburator. It is advised to use a tachometer in conjunction with the vacuum gauge for the entire process.
Thanks, just bought an 84Chevy (350 with an Edelbrock), it ran decent on the long drive back. I pulled the plugs and they're black(mostly) and grey. I will follow your advice.
On a holley 2210 rebuilt the idle air screw on driver's side make no change... passenger side screw shows immediate change...what could be the issue with driver's side. I see no videos on idle air screw issues and what could be it's problem when no adjustment to idle is notice when turning one...any thoughts?
I was thinking at first you could kind of tell he was legit by the way he was holding his cigarette….but once he said “was that right, well it’s close enough for government work” I knew he was.
The reason you use ported vacuum to the distribution.
At idle the throttle blades are closed no vacuumed as you open the throttle blades you pull more vacuumed advance. So at cruising speeds you can pull more advance .
But when you floor it the vacuum drops and the vacuum advance drops off preventing detonation.
You can always pull more advance at low load on the engine cruising speeds.
Incomplete. You did not show where to plug the guage in. What about people who have never done this before? You can't use a vacuum gauge if dot dont know where to plug the darn thing up at. My carb only has one port. It's where the vaccum advance goes. the other carb port has no pressure in any direction, thus. it always stays at 0. There is no where to plug a vaccum guage up on my 350 (that I can find) Only a larger "T" plug into the manifold on the backside of the carb. . and if there was a place I would not know which one to use. I like your videos, but where are places you plug up a vaccum guage. Please use a finger to point to a few specific places please. Many people that have this type issue don't even respond, only the people who have several ports and can do this respond.
tis variable depending on what carb and intake u have. the possibilities are limitless 😮
If you seriously cant just look at the video and trace the rubber hose..... when its obviously doing a close up at one of the parts... Do you even need to try to tune your own engine? Probably not. Let your wife do it. 😂
Vacume gage will diagnose a restricted exhaust plugged cationic converter bad baffles in a muffler.
At idle full ported vacume snap the throttle instantly the vacuum gage should go to close to zero no delay or no wanting to change instantly means a restricted exhaust.
back in the day my dad had JC Whitney vacuum gauges on all the cars for max MPG. The '70 VW Squareback with fuel injection and the '74 Pinto 4 spd were always neck and neck for best mileage.
IA 2001 Chevy S10 4.3 V6 fuel injectin have you ever heard of doing plugs wires and cap you have to reprogram the computer please comment back I know somebody who got theirs done and their mechanic raced their vehicle so much this stuff from the catalytic converter was coming out the exhaust day more or Lass blew up this person's motor Am I right or wrong please comment back in let me know if you know thank you
I remember the good old days when one could start the car with a screwdriver on the solenoid.
Yeah because that energizes your ignition coil too.......
Only thing I ever needed for a vacum gage was for the holley power valve. If you still have a good ear you can tune just by the sound. A tack will help get the best idle but when you snap the throttle you most likely need to turn the idle screws out a 1/4 to half turn more out. This works with a stock cam or a little more of a cam. Big cams forget most that stuff. There is pump shot and a whole a lot of stuff that comes into play here. I have to use a electric vacum pump plus a vacum can so my power breaks will work. At idle with my cam idle at 1200 rpm I only get around 8 inches. Why I have a 3.5 or 2.5 power valve in both blocks on my 850 holley on a 454BBC. With MSD I don't even use a vacum dist. When am at full throttle my vacum is near zero. If I drive long distance I get 12 miles to a gallon. Around town maybe 3 or 5 miles per gallon. Power cost. A good video for a newbie though.
On anything without an ECU I advance the initial timing to the point where I can take off in 2nd uphill and not get pinging. If I have a timing light and want to set up the whole curve, I start Ford's and Chevy's around 30 to 32 total advance and mopars at 34. I then drive it and adjust the advance plates to feel, and again under load, with no pinging.
Nice, how to know about vacuum gauges
Not the whole curve, just centrifical + base.
i’m 38 my dads like this guy we have a machine shop still building race cars... carbureted still... i remember in the 80’s we had a oldmobile station wagon, it had a “fuel economy” gauge in the cluster i said how’s that work? he said vacuum and he smashed the gas it pegged over then came full back to the (+) side and he explained how it worked the more vacuum, the more the butterfly’s are closed the less fuel the more open the less vacuum and worse fuel idk why but i thought that was the coolest thing
Great info, I like how you actually started the engine and showed how to set the idle screws instead of just talking about it... Thanks!
Total ignition advance is basic timing you set by turning the distributor mechanical advance springs weights in the distributor and vacuumed advance add all 3 together you get total ignition timing advance
I thought ported vacuum advance was something that cars in the 70's used to try to improve emissions, not manifold.
nope
@@UncleTonysGarage That's an argument I can't find a answer to. My 67 Pontiac Tempest uses manifold vacuum from the factory. I've tried setting it up ported and it runs better on manifold.
My 1969 400 pontiac runs better on manifold vacuum also. Depends on the engine, do what works best for you.
Gm cars used manifold vacuum up until the 70’s when they switched to ported to raise exhaust temps to help burn off more emissions. I had a 1968 327 in a truck that always ran hot when set up with ported vacuum. Switched to manifold and temps came down and off idle power was way up.
@@ramblr1959 exactly, ported was just an emissions bandaid
All the performance gurus say manifold vac for advance, ive been back and forth with this for 40 yrs, what gives?
As far as manifold goes there's really little use to having your vacuum advance all at once off idle. Ported makes sense because the advance comes in while at cruising speed, so your timing would ultimately be in the beneficial 45ish range at cruising.
Back to the comment section Uncle Tony, very nice!
Used to back mine up against the cherry tree to set it by vacuum. Cherry trees work best. It only makes sense.
@3:44 "It's close enough for government work.." As a guvinment employee, I can attest to that.
My dad was trained as a mechanic. He did all of his maintenance and most engine repairs. He always tuned an engine with just a vacuum gauge, no timing light. He taught me a lot but I always had to use a timing light because I couldn’t get it right with a vacuum gauge. That cars I tuned were a 70 AMC Gremlin 232, 70 AMC Ambassador 360 and a 78 Honda Civic CVCC. After that, things got to complicated for me with all the electronics involved. This video brought back fond memories of all my dad taught me.
You keep this up and someone is bound to learn something!!!! Good on ya!!!
THANK YOU! for covering this and answering questions I had from the last video. Plus I look forward to seeing Bottle Rocket and the slant 6 Dart run. I'm curious to see what kind of numbers they run. You and Uncle Cathy keep up the great work! 😁
Uncle Tony, were is your egr valve, that thing will fail emissions tests in Ontario Canada.
The car is so old it doesn't have EGR. Its a 66 or maybee 67. There were no emissions back then.
Would love to see the results on a choppy cam💪
Pulling 16 and 1/2 inches..........
That would be stretching it.
Ouch!
I’ve always set my timing by manifold vacuum, with the vacuum advance disconnected, and backed off by 5 inches of mercury to account for ignition advance under acceleration and higher RPM. With a performance engine, I found that I had to back off the timing just a tad more to keep it from detonating, pinging and make it easier to start, but it usually isn’t by very much. Setting timing with the timing light was never really an option for me because the engines that I had used aftermarket camshaft, various different compression ratios and everything else was pretty much is thrown together so I really couldn’t set timing with a timing light according to any recommendation.
And that's why you set timing to total and let initial fall where it will. If more initial is needed, time to curve the distributor and narrow the advance range.
@@UncleTonysGarage If you have a large cam you can also use your manifold vacuum for the vacuum advance. If will pull that idle timing forward a bit for a smoother idle in a large cam situation. On stock engines they used ported vacuum because the advance would be too far at idle and you would be making NO based emissions they didn't like. When you have a low vacuum from a big cam the manifold vacuum and a very quick short advance curve helps a lot.
Hi UT! I have a billet distributor no vacuum advance. Where/what do I hook up my vacuum guage to? Holley 4160 750 cfm double pumper with vacuum secondaries. Thank you Uncle Tony.
This comment of mine is old and I now understand what to do. My new Holley came with a "timed port" for Vac Advance I see. Mine is now plugged and my vac gauge was plugged into the manifold port. Tuning this was a breeze and highly recommended alond with UT timing tips. Thanks UT!
2:28 did he just break wind?, he better check his draws, sounds like bad back pressure, lolof
🤡 I tried it but when the turbo spools up the gauge freaks out and it blows the hose off.
Thanks for the good info, can you do a video on diagnosing engine problems with a vacuum gauge.
Took me 64 years to find someone who knew what they were talking about,……and could (between spitting, shaking and thinking faster than any Ferrari mechanic,) teach me in four point something minutes, the most valuable, take it anywhere, knowledge that you can get! I don’t care what you wear, Tony, you just gained a believer!!!
I like how my '98 Ford 4.2 runs stuff with vacuum. The '03 4.2 that I got out of the yard had electronic IMRC controls. I just had to use my '98 upper intake, harness, fuel injectors and IMRC actuators on the '03 block, lower intake and heads. Had to do surgery to relocate the knock sensor though. And switch around a couple sensors. And use the '98 EGR and heater tube. Got the battery tray in today. First start maybe tomorrow. Can anyone recommend good explosion insurance?
UT starts with a stated 16" of Vac and ends with 14" on the gauge. ??? Each hash mark is 2" is it not?
Each hash is one inch. He started with it bouncing between 16.5 and 17. He ended with it solid at 17 inches. Zero is towards clockwise, more vacuum is counterclockwise on that gauge.
Over whelmed by ads..come on man. Too much.
Do not get me wrong..I do not kneel..love you uncle tony..but fk me already.
I love this channel. So many cool nuggets of information and tips. I'm a big 80s-90s euro guy, but I did own a 74 "Gold" 318 Duster for about a year. Was too young, an inexperienced to properly rebuild it so I sold it. Eight years later after watching much of this channel, I'm getting excited to give it a try once again.
When I was young I would always set my timing with a vacuum gauge. I'd increase timing by advancing the distributor for maximum vacuum and when the vacuum started to fall off I would reduce it by 1 inch of mercury. I would then recheck the timing with my timing light. worked for me!
It would take a couple hours to explain all the tuning points on a holley carb lol. I tried breaking it up into different videos on the channel and Im still not done! Good work uncle tony!
My Model T doesn't have any vacuum ports...
Hey I hope to hear back from you, I’m stumped. I have a stock 350 sbc with low miles. It is a GM crate engine. The issue I’m having is the engine is bogging out over 3000 rpm’s. Things I’ve done chasing this issue, new distributior, new plugs and wires, set timing at 14 initial, replaced mechanical fuel pump, replaced fuel filter, replaced fuel tank sock, replaced all rubber hoses, made sure gas tank is venting properly, replaced air filter, and rebuilt carburetor. I’m honestly baffled and worried it might be an internal problem. Also I removed the fuel pump push rod and stuck my bore-scope camera in the hole and had a buddy bump the engine over to inspect the cam lob to make sure it wasn’t flat. Everything checks out fine. The carb I am using is a Holley 1450 with vacuum secondaries, it is an old carb that I’ve rebuilt before. Also plugs look great, doesn’t appear to be to lean/rich. And the timing looks mint on the ground strap. Could it be a burnt valve? Or is the old flat tappet cam giving up? Idk, hope to hear back from you.
i found this video very helpful. I am new to carbureted vehicles because i was born well after fuel injection came out. I recently picked up a 1968 El Camino SS with a 396 Big Block and have been getting acclimated. Thanks for putting out this content. It is very straightforward and helpful.
Uncle Tony, talk about perfect timing for this video! I'll be taking an extensive road trip soon with an old carb engine and was looking to do a solid tune on my Weber carb before I head out. I had been planning on doing some research on this but haven't done anything yet. I purchased a vacuum gauge from china freight the other day and was hoping to get this done sometime during this week.
Wouldn't you know it, you uploaded a video that answered all the questions I had and explained it thoroughly for a rookie like myself who's hoping to keep the carb alive!
I really appreciate this video and can't wait to dive into this form of fine tuning myself soon!
I'm also gonna be using this method to help my friend fine tune his carb on a 5.0 mustang from an engine swap we recently did on it.
Really appreciate your videos! They're definitely better than enough for government work. Hahah.
I appreciate your videos and thanks for what you do!