same here, I put a Mikuni on an MGB and it would do this stuff so I just put the SUs back on boy was that a bummer Mikuni, remember looking to see what happened when you 'showered down' didn't ever see that squirt of gas...grr. It was new out of the box too.
seen a car with a sticker sayinG.- I LOVE CARS MORE THAN WOMEN in the rear I CHANGED MY WIFE FOR THIS CAR. and in the door: I kiss my dog not women,, well i can make an exception and kiss this car.
Dealing with this right now. My car wouldn’t be running if i wasn’t watching this channel. Shop told me i needed a new engine when after watching tonys videos i discovered that it was a fuel issue. Replaced lines and new carb and never looked back. Thanks.
@puttsr believe it or not... there's a few of us that follow UT because he reminds us of old ways. They do work. Hit him up in the next tech talk.. he'll help. If he don't solve it.. he'll send you to the one that can explain.
You may think a 30min video is expansive but I find it very informative and I learn something in everything you post. Thanks for taking the time to share your knowledge.
So much knowledge and experience in this one video would've taken me months to discover the hard way, like I did lol. Thank you Tony for carrying the torch
I really wish that the internet, TH-cam and Uncle Tony were available to me 40 years ago when I was in my 20’s and had my ‘65 Dart and ‘67 A-100 van. I know and experienced exactly the things you talk about in this video. It was maddening. Especially on the A-100 (318/auto, I wish I still had it). The timing light told me one thing, but it ran best when I adjusted the distributor by hand to where it liked. It all makes sense now. Hopefully, I can, one day before I’m gone, have another “analog” Mopar to tinker with and enjoy. Thanks, Tony. ❤
We all had to learn carburetors, its just that old guys like Tony and I learned it a long time ago, and younger people are learning it now without the massive wealth of information that was in magazines 30-60 years ago. Young people have the internet, and its full of people who have no freakin clue but tell it like they know what they're talkin about.
Amen to that brother... I'm appalled at the Facebook engine build groups that sling so much B.S. Unfortunately many self admitted young first time builders are asking questions and getting answers that just thicken the confusion. I'm no pro but at 62 years old I've learned how much i don't know. Guys like uncle Tony, Ben Alameda, Eric Weingartner, David Vizard and a few others are real teachers who i try and steer the new guys towards but I'm afraid many never get there. "How to hot rod your sbc" is priceless but books are viewed as ancient. Teaching is sooo difficult
Us well aged hot rodder’s also had the added benefit of having more well aged (dare I say vintage) hot rodder’s to learn from. Thankfully I didn’t think I knew everything when I was young… and soaked up as much knowledge like a sponge as I could. My dad forgot more than I’ll ever know.
I know you'll agree with this, many people will claim that manifold vacuum advance is better, yes for decreased exhaust temperature, but I've always found that for performance ported vacuum advance is better. My experience in industrial big block tuning says with manifold vacuum advance you may experience an off idle stumble and I'm absolutely sure that is the case for many many other engines.
Tony, true story.. Its been about 15 years ago now, I was working on my 70 vw carbs at the shop I was working at. At this time a man I knew brought in a guy my age who'd just graduated the local universities automotive program which is recognized as one the best in the country, he actually graduated the program with high honors. Well he had seen me working on my carbs and he was absolutely amazed and told me he had no idea how carburetors worked. I asked him, if you just graduated the auto program what were they teaching you? And his answer, fuel injection.. electronic fuel injection was the only thing taught in that program, they didn't even touch base on carbs
Great advice on the newer dial back lights. We purchased a HF model… 4-5 degrees off. I’d add that if using a light, after setting timing with vacuum disconnected, re-connect the vacuum line and watch the strobe as you blip the throttle. You should see the dampener mark jump ahead. This will also verify what the type of distributor and if you have it connected to the correct type of vacuum source. Jumps ahead- good. Jumps back- your distributor wants ported and is hooked up to manifold.
Great video once again. Couldn’t be explained any better. My distributor was seized . Once I freed it up and advanced my timing all bogging was gone and tires were spinning joyfully!!
DIESELING ENGINE: This can caused by a number of things: 1) Too fast an idle speed. 2) Too rich fuel mixture. (Long-term causing carbon build up which glows hot and ignites fuel after the ignition circuit has switched off) 3) Too lean a fuel mixture at top end from incorrect jetting or airleak, casuing the engine to overheat. The fuel/air mixture could be heated to the point that it self-ignites, causing the diesel run-on effect. 4) Timing is out. The timing itself won’t cause the run on as the ignition is switched off when the run in occurs. However timing too far advanced can cause an overheating engine which can attribute to over-run. USUALLY its this. Should have made this number one. 5) Lower octane fuel could aggravate the problem, because it will self-ignite quicker than a higher octane fuel. But it alone won’t cause the problem. 6) Carburetor idle stop Solenoid . 7) Sparkplugs have a temperature range. Are you running the right ones for your engine spec? Also are they clean and gapped correctly?
Good video Uncle Tony. I agree on power timing being best. I'd start out advancing distributer as far as possible to the point of starter telling me it wasn't happy. Then I'd brake torque car and listen for ping. I'd back it down to the point of not pinging then take it for a ride and finish adjustment after testing under load 4-5 times. Always had my wrench to snug distributer once I found engines happy place.
I used your power tuning method on my mild 318! I saw that on an older video of yours. So I don’t know what my timing is set at but it sure runs good! Also,I’m running a tuned Edelbrock 500 and after experimenting I found mine runs better using manifold vacuum. Quite a snappy set up now. Running a Comp 268 cam, Edelbrock performer intake, hei distributor and coil and a full 2.5inch exhaust. My biggest improvement was upgrading the diff ratio from 2.92 to 3.45. By far better now.
Unmentioned but important. Many of these supposed issues are non-problems that can be made mitigated by pedal usage/and understanding your particular combo. Unless you grew up with carburetors this can be a gigantic challenge to today's modern tech lovers.
I manage a group of forklift dealer service departments. We hire young guys out of trade school and they've never seen a timing light or adjusted valves. What's worse is most of them don't know how to use a multi-meter or scan tool either.
#uncletony'sgarage THIS VIDEO BELONGS IN THE SMITHSONIAN!!! At between 6:00 and 6:49, brought my 38 year old self back 20 years to a G body build I did, crank and crank and crank no start. After 1am I realized I wired the fuel pump wrong and my 383 jumped into life 😅😅😅 🤘🤘🤘
The way I find true top dead center without a piston stop or a degree wheel is similar. Bring 1 up to close to TDC compression stroke get long zip tie (or something that CAN NOT fall into the cylinder). Continue to turn the engine clockwise (normal rotation) until you feel the zip tie stop moving up. Mark the dampener (I use 0 on the timing pointer). Now continue to slowly turn the engine clockwise until you feel the zip tie start to go down and mark the dampener again. True TDC is at the exact mid point between these two marks. I go back and repeat this a couple yours because I'm neurotic like that but this has the fastest, easiest, and most precise way I've found to to locate TDC without tools. Obviously a degree wheel and piston stop tool is more accurate but this way gets you really close. And don't be surprised if your pointer doesn't exactly point at the mid point between marks which is true TDC some will some won't. If it's significantly off your dampener has slipped and needs replaced. What you're doing is finding the mid point of piston dwell at TDC.
Accelerator pump, timing AND I see a lot of guys running way to lean, this also causes the same issues. I have changed jets on hundreds of carbs for friends that had no idea how to, or even thought of jetting a new out of the box carb. They just buy them, bolt them on, then wonder why the car runs poorly.
This video described exactly what I'm experiencing with my 85 Jeep Grand Wagoneer. It stumbles at take off and then under load it's knocking. Factory spec calls for 19 degrees BTC and the brackets happen to block clear vision to actually set the timing accurately. I will be trying the power setting as you described today and I'm looking forward to it! Thank you!!
I remember reading all of this in Chilton's manuals 30 years ago on how to tune up your car properly. This type of knowledge is becoming lost because so few of us drive cars with carbureted engines anymore. One comment. On a Slant 6 you can't advance the base timing very much. I believe it's because of the long stroke the engine has. On most engines you can advance the base timing a lot and you're fine. On a Slant 6, in some years in the 70s, the spec was top dead center. You could advance it 4 or 5 degrees but that was about it.
I read David Vizards book and he stated at idle the vacuum lowers the boiling point of fuel allowing the mixture to vaporize. When the vacuum falls due to opening the throttle the fuel reverts back towards being a liquid. The accelerator pump compensates the lean condition due to the transfer of the state of the fuel.
In a downdraft Weber the transition "slot" is fed by the idle jets so don't listen to anyone telling you the idle jet doesn't effect driving. It will cause a major stumble at mid to high rpm.
Uncle tony I'd like to correct you on the fact that Motorcycle CV carbs do infact sometimes have a acclerator pump they get used on scooters, mopeds, superbikes and even harley used them on their Mikuni CV carbs for better throttle response they can be tuned aswell
@@jasonbusch3624 they can be handy and a pain when they decide to not function as intended rich mixture conditions or as uncle tony said a stumble or stall off idle circuit
@s.a.f.r.a6403 I started working on motorcycles back in 1991 and have worked in shops my whole life. I have a ear for lean conditions and engine problems. My buddy stopped by on his Harley and I told him it wasn't running right. A week later he stopped over with it and it had fouled a sparkplug and was only running on one cylinder. I checked compression and spark it was good so we put a new sparkplug in it and it lightly smoked out the exhaust for about 15 minutes, but was running great again. The old sparkplug electrodes were really wore and rounded, had a lot of miles on them.
People like Tony an his followers fail to realize new motorcycles two stroke or four, have carbs or efi as options in modern times. But they claimed old school lol. Also a tiny 150cc modern dirt bike has a bigger carb with more airflow that a slant 6 3.7liter single barrel carb. Pilot jets,main jets,leek jets, needle position,accelerator pump adjustment in modern KTM or Hondas etc is not old school they make them brand new in 2024 or efi of u want.
I am glad to hear you clarify vacuum advance timing based on manufacturer because everyone says one or the other and get into their camps as to why and I am so glad to learn things were based on manufacturer.
Nice job Tony, that will help a lot of people. You have amazing knowledge. I get cars other shops have looked at and could not get a stumble out of. Yes, carburetor or ignition. I also get Frankenstein motors in cars bored, stroked, over crammed, over carbed, etc. etc. Also odd swaps, especially GM’s like say a Chevy with a Buick motor or a Pontiac with an Olds motor, just about anything. Yes, if the accelerator pump is working and adjusted properly, most likely ignition timing or an ignition or electrical problem. Might be just me but I have repaired and adjusted many rotten carbs causing stumbling that had good accelerator pumps. A Thermoquad in the distant past comes to mind immediately. Like you perfectly stated, it is nice to know when something is good, like known good carb or known good ignition before someone changed the carb or whatever they did. I will give anyone a tip on a stumble I found. I get a hot rod in, barely touch the gas and it stumbles, mash the gas, it either takes off like a race car or it drowns and dies, it had been around to a lot of shops. Customer said he bought it that way, said the seller thought it was the carb needing adjustment but he had been driving it that way for years. I could see someone had been all over the arm bending for the accelerator pump but it appeared to be working well. So I am thinking ignition. This is a very old hot rod with some kind of replacement 350 with a cam, aluminum heads and manifold. I see it has a chrome timing marker and this thing is tiny and although true to top dead center on the zero mark was not spaced/marked correctly after that. Was not the problem but could have been. The problem was the 12 volts going to the distributor was keyed voltage and weak. At idle the engine is spinning the alternator the slowest giving anything and everything the weakest voltage it will get. I find it has an all out race ignition and it needed voltage as high as it could get. The resistor wire had been replaced with a nice thick regular wire. It was a half volt low, motor running or not, reving up or not. Keyed voltage was low anywhere, all the old fuse system was intact. The fix was to use the keyed voltage to run a relay to hit the high performance ignition with fused full battery power and it turned that stumbling, spitting dying thing into a tire fryer. The cam seemed big so I timed it to vacuum first. Then I took a piece of masking tape and taped it over the timing mark indicator on my 350 and rubbed in the marks, transferred that to customer motor indicator lining up the zero marks so I would know where it actually was set. It was a lot of timing, I took just a smidge more out. Anyway, that fixed it, slam dunk on the tune, the motor ran like a race motor, snappy, pulled hard, tested good, didn’t want to break anything. Very happy customer when he left. A rare problem but I have run into that type thing a few times now so hopefully that may help someone with a stumble.
So much gold in this one video! What solved my issue was using a quality rebuild kit. The rubber on the auto parts store accelerator pumps is crap and as soon as I had a good pump in the carb it was fine.
One of my favorite sources of info for chevrolet cars was the book put out by the factory on performance upgrades and tuning for chev 4 cylinder and V8s.
Don’t forget about a weak EGR valve. If spring is weak, valve will just pop open and cause a lean mixture. Just unplug EGR and test drive vehicle. If it goes away, just leave it unplugged or replace it.
In queens we used to get a guy in the car put it in drive with the break smashed down, the guy under the hood would turn the distributor until the the tires started to break traction. Lock it down and your ready to go.
@jerryakbar6147 another old redneck way... is listen to the engine at idle. If it's hitting correctly, (just under the rattle sound). Just rev it to 2500 ish.. turn it back and forth until happy.. adjust depending on application. That will make it run. Not correct.. but a good base point. Until fuels change of course. Lol
Timing curve , fuel curve . Wether it's analog or EFI it has to work properly. Your timing has to move as fast as the fuel curve. I learned the hard way but it's the best way to learn.
My 66 Dodge Dart had a bad stumble in sub-zero temps. So I fabricated an exhaust manifold shroud then connected it to the air cleaner with a flex tube. It fit perfectly into the snout just by chance!
Thank you. This is what I visit your channel for. Older mechanics looking out for younger mechanics is what our culture is about. Younger mechanics have an interest in older tech with less electronics. Plus it's awesome seeing and old car or truck still on the road.
Another good video. Watching your videos brings back memories of problems I encountered years ago as well as what I found was the solution to those problems.
I don't have any stumble, bog or any other troubles. But tuning has always interested me, so you got a view. You just reminded me that I haven't really finished the setup on the Edelbrock AVS2 that came on my SBC. Might be able to do some timed runs and get the jetting right. Once it's there I can see how it does using your power timing move. I have always just gone 34 to 36 degrees all-in on my 350's cause it's safe and works. I suppose I should be trying to get all the juice out of my car. Otherwise I'm leaving power (fun) on the table.
On Ford pushrod engine, I attach a piece of stiff wire,bent to dist side,near the Dist. Mark dist with white marker. Make fine adj roadside by moving dist.
I had a customer with a 78 Monte Carlo w/ 305 V8. Complaint was a major lack of power. It would have good throttle response, but then it barely had any power at all. It had all the symptoms of a plugged cat converter. After replacing the cat and not solving any problems I discovered that the centrifugal advance was totally stuck. Removing the distributor and freeing up the weights made it run like new! Why did it still have some pep off the line? The *ported* vacuum advance gave just enough timing to take off, but as you opened the throttle more, that vacuum dropped off, and timing was back to where it was at idle. I learned quite a bit about timing after that! BTW, I have always used the "advance til it pings and then back it off" method, with rarely any problems. Glad I didn't try that on the Monte!
This worked for me -- on a boat 351W -A vacuum gauge reading of 20 in. Hg Edelbrock 1409 Carburetor Step-Up Springs--stock was orange springs with bog than changed to the silver springs=8" bog gone
I experienced this with a slightly modified 360ci FE engine. and fought it for quite some time. the engine was bored .030 over stock with a 539 lift 280° duration camshaft. with four barrel intake manifold and carburetor. I tried multiple carburetors and distributors but still had a lean condition issue. where it would cough up though the carburetor. and on Fords ported vacuum is used with automatic transmissios. and manifold vacuum is used on manual transmissios. and this vehicle had a manual transmission. I finally found that it was because I had a speadbore carburetor. using an adapter on a straight bore manifold. and the back cylinders would lean out because the primary throttle plates couldn't feed the rear most cylinders. because of the straight bore manifold.
I've gotten turned around on tuning cars with accelerator pump problems it's just like the mechanism in a spray bottle like Any kind of spray bottle like Cleaning products windex come in or any kind of just bottle you fill with whatever same kind of mechanism If you pull the trigger you don't have a good solid squirt. I was always taught that it should be a clean spray throughout the throttle movement not A Half Squirt and then a dribble. Also need to make sure that the fuel bowl is full when you're checking this cause you cant do it a bunch of times and get yourself turned around because there's no more fuel in the bowl than the engines flooded and it won't start but anyway I hope you get my point I love this video Tony. This is the kind of stuff. That was lost in the generations after you.
20:07. While yes I agree.. it also made sure the distributors vacuum advance functions were all working correctly. If you did all this and still had issues.. put a timing light back on it with the advance hooked up and rev it up a little to make sure.. basic stuff to us.. but thought I'd share just incase.
Bad points gap can really mess up the spark timing, I have learned the hard way. A small amount of point gap error can cause the spark to come far too early, or far too late, and really mess up your timing!
Hey Tony, I totally agree with you on dial back timing lights. I have a Craftsman timing light from the 80s that I've had for years that I bought, that is the dial back style and I found it not being accurate at all so I took it apart and bypassed (removed the pot/dial). After that it works perfect and still does today. You just can't beat the old tools as long as you know how to use them. Later
The problem I see with setting initial timing by vacuum or by ear is it doesn't take total timing into account. Distributor mechanical advance amount are all over the place with OEM distributors. Most times you'll find 15 degrees or so runs really nice at idle. If that distributor was set up originally for a couple degrees advance, it'll be way over once the rpms come up. If the original spec was 2.5 degrees ATDC like my 68 D200's 318 it's WAY over. Jump to my 81 W250 with a 318 auto the fender tag says 15 BTDC factory spec. Same basic engines, vastly different amounts of built in mechanical advance! So I never recommend those methods unless you check the all in mechanical. Best bet, find the initial and all in it wants, mod the distributor to match.
@Joetechlincolns Somewhere around 35ish, but that's not carved in stone! Bore size, compression, combustion chamber design, fuel octane all play into it, plus, whether its naturally aspirated or force fed.
You forgot the off-idle circuit. Off -idle slots transition the carb from idle to main metering. Some early 70s two barrel GM carbs had a screw in the back of the carb under a plug that you were not supposed to remove. They were often set too lean and would cause an off-idle stumble before the accelerator pump had a chance to work. They were called “off-idle air screws” so turning them in richened the off-idle mixture.
great stuff thanks. when you are setting up TDC and adjusting by hand, remove your spark plugs so that you are not fighting compression (especially turning reverse when using the damper bolt),
The timing situation assumes your distributor gear and cam gear are in good shape and limited backlash. Older cars really need that examined and fixed as needed.
I had a problem with an edelbrock carb that was new . It had a bog I did everything to it. It turned out the thermostat temp was way to low no fuel atomization
Well UTG talked me into getting a g body. Said if he wasn't Mopar guy that's all he'd have. Just bought 83 olds toronado. Has a carb and a thousand vacuum lines. Guessing I will be watching lots of his videos know.
What’s your opinion on setting timing on a ported setup, then switching to manifold vacuum? It seems to help start easily and then have lots of timing down low without too much up top. Like a recurve kinda, with better starting possibly. I’m running that on my L20b for now.
Would love you to cover locking out distributors and timing on big cams, ignition and carb tuning. Ive onluy got 5" vacuum at best idling and even a 25 power valve is borederline. Im current running a locked out dizzy set at 40 degrees. That seems to be where it want to be from idle to top end, ut just works great, Any more and it starts to detonate and any less it wont idle!
You should look up the Chrysler Australia engine design plans for the mid 1970s , Chrysler Australia wanted bigger engines , GM Holden was going to import 403 ci Oldsmobile V8s for its Statesman long wheel base model and LE Monaro two door, Ford wanted the 400 V8 that it was going to use the low deck 302/351 Cleveland block it already cast at the Geelong Casting Centre and install a 4.0 inch stroke crank. So Chrysler Australia was looking to jump on the 400 ci band wagon , but a big block B400 was out of the question , so Chrysler was already casting the 215/245 and 265 ci Hemi Six here ( that they also wanted enlarged to 300 ci ) so the plans were drawn up for a 404ci LA based small block . The official Chrysler Australia paperwork listed a 4.10 bore Block Cast in Australia and 3.825 Stroke crank of nodular iron also cast in Australia , with 6 inch rods and pistons to match, the project called for a 6.7 litre V8 for the late 1970s beating Ford and Holden . Several 4.10 bore blocks were cast and one engine assembled . No idea were it is today or if it ever ran . But it's an interesting piece of Chrysler's history , a 6.7 Or 404 ci LA based Small Block Chrysler would have been amazing . All the LA after market parts such as intakes and cams would have fitted , plus a 6.7 litre SB is so much lighter than a B400 . Shame Chrysler Australia never proceed with that engine .
i was born in 82 so most of my driving/adult life society has been injection.... although my dad was a old hotrodder.....mom always had a newer car bud dad stuck to the older stuff from the early 70s and older.....i learned carb adjustment and points dwell way before i was old enough to drive....my firts car was a 49 willys wagon whn i was 14....now im in my 40s and prerty much only drive stuff from the mid 60s and back......now my kids are building classics too.....its wonderful passing this info to the next generation....if we dont its gonna be lost
Always set with a cheap neon timing light. Didn’t know about the difference between ported and manifold vacuum. I also used static timing setting it with a cigarette paper like one does on a motorbike. In retrospect I think I got good results timing my various 60s Chrysler cars but may not have got the GM cars timed right. My 63 383 would chirp the tires shifting from 2nd to 3rd at 85 and that good enough for me. I discovered those cheap timing lights were an excellent was to diagnose a weak or intermittent coil because they relied on the coil for power. Aimed at the firewall you could see when the light wasn’t consistent. Intermittent = bad coil.
lol, I wish I knew more bout engine tuning, more specifically timing in the 80’s driving old $200 dollar beaters. We would never dare stray from the factory recommended settings.
There was a third way to set the timing on car’s with a vacuum advanced distributor, but it did not always produce what I’d call a reliable result. And that was to disconnect the vacuum advance, block off the vacuum line and loosen the distributor locking bolt just enough to move it by hand with the engine running if you had a distributor wrench. Then rev the engine without touching the distributor, and when the distributor moved lock it in place and let it return to idle. The reason I say it did not always produce reliable results, was it could be difficult to get the distributor locked in place before letting the engine return to idle or have the distributor locking bolt loose enough for the distributor to move on its own. Or still have the distributor locking bolt tight enough, to lock the distributor down while holding the throttle at a fast idle in a single twist of the distributor locking bolt. I played with that method of adjusting the distributor in that manner a few times, and the results could be very interesting and sometimes wildly inaccurate. My dad had a strobing timing like that did not have that dial, and it was very accurate as long as the harmonic balancer was in good condition and the correct one for that engine. And had the timing marks in the correct location on the timing chain cover. If not, I had to go buy timing tape, to clock it at TDC.
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I'm watching this to fix a problem I had 40 years ago.
And it's already fixed
same here, I put a Mikuni on an MGB and it would do this stuff so I just put the SUs back on boy was that a bummer Mikuni, remember looking to see what happened when you 'showered down' didn't ever see that squirt of gas...grr. It was new out of the box too.
seen a car with a sticker sayinG.-
I LOVE CARS MORE THAN WOMEN
in the rear
I CHANGED MY WIFE FOR THIS CAR.
and in the door:
I kiss my dog not women,, well i can make an exception
and kiss this car.
Dealing with this right now. My car wouldn’t be running if i wasn’t watching this channel. Shop told me i needed a new engine when after watching tonys videos i discovered that it was a fuel issue. Replaced lines and new carb and never looked back. Thanks.
@puttsr believe it or not... there's a few of us that follow UT because he reminds us of old ways. They do work. Hit him up in the next tech talk.. he'll help. If he don't solve it.. he'll send you to the one that can explain.
Really good Master Tech video UTG.
You may think a 30min video is expansive but I find it very informative and I learn something in everything you post. Thanks for taking the time to share your knowledge.
So much knowledge and experience in this one video would've taken me months to discover the hard way, like I did lol.
Thank you Tony for carrying the torch
I really wish that the internet, TH-cam and Uncle Tony were available to me 40 years ago when I was in my 20’s and had my ‘65 Dart and ‘67 A-100 van. I know and experienced exactly the things you talk about in this video. It was maddening. Especially on the A-100 (318/auto, I wish I still had it). The timing light told me one thing, but it ran best when I adjusted the distributor by hand to where it liked. It all makes sense now. Hopefully, I can, one day before I’m gone, have another “analog” Mopar to tinker with and enjoy. Thanks, Tony. ❤
We all had to learn carburetors, its just that old guys like Tony and I learned it a long time ago, and younger people are learning it now without the massive wealth of information that was in magazines 30-60 years ago. Young people have the internet, and its full of people who have no freakin clue but tell it like they know what they're talkin about.
You mean there's BS and nonsense on The Interwebs? NO,can't be.Who would do that?
I only used holles on cars but, i mastered jetting and tuning motocycle carbs.
Amen to that brother...
I'm appalled at the Facebook engine build groups that sling so much B.S.
Unfortunately many self admitted young first time builders are asking questions and getting answers that just thicken the confusion.
I'm no pro but at 62 years old I've learned how much i don't know.
Guys like uncle Tony, Ben Alameda, Eric Weingartner, David Vizard and a few others are real teachers who i try and steer the new guys towards but I'm afraid many never get there. "How to hot rod your sbc" is priceless but books are viewed as ancient.
Teaching is sooo difficult
@@dddevildogg I know right! Just found out myself!
Us well aged hot rodder’s also had the added benefit of having more well aged (dare I say vintage) hot rodder’s to learn from. Thankfully I didn’t think I knew everything when I was young… and soaked up as much knowledge like a sponge as I could. My dad forgot more than I’ll ever know.
I know you'll agree with this, many people will claim that manifold vacuum advance is better, yes for decreased exhaust temperature, but I've always found that for performance ported vacuum advance is better. My experience in industrial big block tuning says with manifold vacuum advance you may experience an off idle stumble and I'm absolutely sure that is the case for many many other engines.
Good information for someone who is new to carbureted engines. Or refresher course for us old guys.
Good old tech is way more interesting than modern computer tuning!👍👍👍
Tony, true story.. Its been about 15 years ago now, I was working on my 70 vw carbs at the shop I was working at. At this time a man I knew brought in a guy my age who'd just graduated the local universities automotive program which is recognized as one the best in the country, he actually graduated the program with high honors. Well he had seen me working on my carbs and he was absolutely amazed and told me he had no idea how carburetors worked. I asked him, if you just graduated the auto program what were they teaching you? And his answer, fuel injection.. electronic fuel injection was the only thing taught in that program, they didn't even touch base on carbs
Being an experienced engine tuner is much like being a great lover. There is science to it, but at its best its a mystical intuition.
Yeah the go button is generally in the same spot but a little different each time eh?
Great advice on the newer dial back lights. We purchased a HF model… 4-5 degrees off.
I’d add that if using a light, after setting timing with vacuum disconnected, re-connect the vacuum line and watch the strobe as you blip the throttle. You should see the dampener mark jump ahead. This will also verify what the type of distributor and if you have it connected to the correct type of vacuum source. Jumps ahead- good. Jumps back- your distributor wants ported and is hooked up to manifold.
Great video once again. Couldn’t be explained any better. My distributor was seized . Once I freed it up and advanced my timing all bogging was gone and tires were spinning joyfully!!
The title of the video sounds like a car I had when I was 17😂
Great video, Tony, there aren’t many of us around anymore
You can use the sliped balancer simply by remarking it with a white marker that will work short term
DIESELING ENGINE: This can caused by a number of things:
1) Too fast an idle speed.
2) Too rich fuel mixture. (Long-term causing carbon build up which glows hot and ignites fuel after the ignition circuit has switched off)
3) Too lean a fuel mixture at top end from incorrect jetting or airleak, casuing the engine to overheat.
The fuel/air mixture could be heated to the point that it self-ignites, causing the diesel run-on effect.
4) Timing is out. The timing itself won’t cause the run on as the ignition is switched off when the run in occurs. However timing too far advanced can cause an overheating engine which can attribute to over-run. USUALLY its this. Should have made this number one.
5) Lower octane fuel could aggravate the problem, because it will self-ignite quicker than a higher octane fuel. But it alone won’t cause the problem.
6) Carburetor idle stop Solenoid .
7) Sparkplugs have a temperature range. Are you running the right ones for your engine spec? Also are they clean and gapped correctly?
Good video Uncle Tony. I agree on power timing being best. I'd start out advancing distributer as far as possible to the point of starter telling me it wasn't happy. Then I'd brake torque car and listen for ping. I'd back it down to the point of not pinging then take it for a ride and finish adjustment after testing under load 4-5 times. Always had my wrench to snug distributer once I found engines happy place.
I used your power tuning method on my mild 318!
I saw that on an older video of yours. So I don’t know what my timing is set at but it sure runs good!
Also,I’m running a tuned Edelbrock 500 and after experimenting I found mine runs better using manifold vacuum. Quite a snappy set up now. Running a Comp 268 cam, Edelbrock performer intake, hei distributor and coil and a full 2.5inch exhaust. My biggest improvement was upgrading the diff ratio from 2.92 to 3.45. By far better now.
Sweet.
There is always something with carburators. The time is passed on them, however, I have a mustang with autolite carburator. Pain in the neck.
Unmentioned but important. Many of these supposed issues are non-problems that can be made mitigated by pedal usage/and understanding your particular combo. Unless you grew up with carburetors this can be a gigantic challenge to today's modern tech lovers.
I manage a group of forklift dealer service departments. We hire young guys out of trade school and they've never seen a timing light or adjusted valves. What's worse is most of them don't know how to use a multi-meter or scan tool either.
#uncletony'sgarage
THIS VIDEO BELONGS IN THE SMITHSONIAN!!!
At between 6:00 and 6:49,
brought my 38 year old self back 20 years to a G body build I did, crank and crank and crank no start.
After 1am I realized I wired the fuel pump wrong and my 383 jumped into life 😅😅😅 🤘🤘🤘
Always great information. I grew up with carbs and I still learn great stuff from you Tony.
The way I find true top dead center without a piston stop or a degree wheel is similar. Bring 1 up to close to TDC compression stroke get long zip tie (or something that CAN NOT fall into the cylinder). Continue to turn the engine clockwise (normal rotation) until you feel the zip tie stop moving up. Mark the dampener (I use 0 on the timing pointer). Now continue to slowly turn the engine clockwise until you feel the zip tie start to go down and mark the dampener again.
True TDC is at the exact mid point between these two marks.
I go back and repeat this a couple yours because I'm neurotic like that but this has the fastest, easiest, and most precise way I've found to to locate TDC without tools.
Obviously a degree wheel and piston stop tool is more accurate but this way gets you really close.
And don't be surprised if your pointer doesn't exactly point at the mid point between marks which is true TDC some will some won't. If it's significantly off your dampener has slipped and needs replaced.
What you're doing is finding the mid point of piston dwell at TDC.
Accelerator pump, timing AND I see a lot of guys running way to lean, this also causes the same issues. I have changed jets on hundreds of carbs for friends that had no idea how to, or even thought of jetting a new out of the box carb. They just buy them, bolt them on, then wonder why the car runs poorly.
This video described exactly what I'm experiencing with my 85 Jeep Grand Wagoneer. It stumbles at take off and then under load it's knocking. Factory spec calls for 19 degrees BTC and the brackets happen to block clear vision to actually set the timing accurately. I will be trying the power setting as you described today and I'm looking forward to it! Thank you!!
Want to add, to much pump shot can cause hesitation as well as to little. It's all about finding that happy medium.
I remember reading all of this in Chilton's manuals 30 years ago on how to tune up your car properly. This type of knowledge is becoming lost because so few of us drive cars with carbureted engines anymore. One comment. On a Slant 6 you can't advance the base timing very much. I believe it's because of the long stroke the engine has. On most engines you can advance the base timing a lot and you're fine. On a Slant 6, in some years in the 70s, the spec was top dead center. You could advance it 4 or 5 degrees but that was about it.
Great info! The only thing I think you didn't cover is which way is advanced vs the opposite which I figure I can't say due to silly filtering.
Master of carburator cars.
I read David Vizards book and he stated at idle the vacuum lowers the boiling point of fuel allowing the mixture to vaporize. When the vacuum falls due to opening the throttle the fuel reverts back towards being a liquid. The accelerator pump compensates the lean condition due to the transfer of the state of the fuel.
In a downdraft Weber the transition "slot" is fed by the idle jets so don't listen to anyone telling you the idle jet doesn't effect driving. It will cause a major stumble at mid to high rpm.
Uncle tony I'd like to correct you on the fact that Motorcycle CV carbs do infact sometimes have a acclerator pump they get used on scooters, mopeds, superbikes and even harley used them on their Mikuni CV carbs for better throttle response they can be tuned aswell
You are correct. Most newer 1980's and up 4 stroke motorcycle and atv carburetors have an accelerator pump. Most 2 cycle carburetors do not.
@@jasonbusch3624 they can be handy and a pain when they decide to not function as intended rich mixture conditions or as uncle tony said a stumble or stall off idle circuit
@s.a.f.r.a6403 I started working on motorcycles back in 1991 and have worked in shops my whole life. I have a ear for lean conditions and engine problems. My buddy stopped by on his Harley and I told him it wasn't running right. A week later he stopped over with it and it had fouled a sparkplug and was only running on one cylinder. I checked compression and spark it was good so we put a new sparkplug in it and it lightly smoked out the exhaust for about 15 minutes, but was running great again. The old sparkplug electrodes were really wore and rounded, had a lot of miles on them.
People like Tony an his followers fail to realize new motorcycles two stroke or four, have carbs or efi as options in modern times. But they claimed old school lol. Also a tiny 150cc modern dirt bike has a bigger carb with more airflow that a slant 6 3.7liter single barrel carb.
Pilot jets,main jets,leek jets, needle position,accelerator pump adjustment in modern KTM or Hondas etc is not old school they make them brand new in 2024 or efi of u want.
@@apocolypse11 worked on both newer stuff easier to work on older stuff fights back
I am glad to hear you clarify vacuum advance timing based on manufacturer because everyone says one or the other and get into their camps as to why and I am so glad to learn things were based on manufacturer.
Nice job Tony, that will help a lot of people. You have amazing knowledge. I get cars other shops have looked at and could not get a stumble out of. Yes, carburetor or ignition. I also get Frankenstein motors in cars bored, stroked, over crammed, over carbed, etc. etc. Also odd swaps, especially GM’s like say a Chevy with a Buick motor or a Pontiac with an Olds motor, just about anything. Yes, if the accelerator pump is working and adjusted properly, most likely ignition timing or an ignition or electrical problem. Might be just me but I have repaired and adjusted many rotten carbs causing stumbling that had good accelerator pumps. A Thermoquad in the distant past comes to mind immediately. Like you perfectly stated, it is nice to know when something is good, like known good carb or known good ignition before someone changed the carb or whatever they did. I will give anyone a tip on a stumble I found. I get a hot rod in, barely touch the gas and it stumbles, mash the gas, it either takes off like a race car or it drowns and dies, it had been around to a lot of shops. Customer said he bought it that way, said the seller thought it was the carb needing adjustment but he had been driving it that way for years. I could see someone had been all over the arm bending for the accelerator pump but it appeared to be working well. So I am thinking ignition. This is a very old hot rod with some kind of replacement 350 with a cam, aluminum heads and manifold. I see it has a chrome timing marker and this thing is tiny and although true to top dead center on the zero mark was not spaced/marked correctly after that. Was not the problem but could have been. The problem was the 12 volts going to the distributor was keyed voltage and weak. At idle the engine is spinning the alternator the slowest giving anything and everything the weakest voltage it will get. I find it has an all out race ignition and it needed voltage as high as it could get. The resistor wire had been replaced with a nice thick regular wire. It was a half volt low, motor running or not, reving up or not. Keyed voltage was low anywhere, all the old fuse system was intact. The fix was to use the keyed voltage to run a relay to hit the high performance ignition with fused full battery power and it turned that stumbling, spitting dying thing into a tire fryer. The cam seemed big so I timed it to vacuum first. Then I took a piece of masking tape and taped it over the timing mark indicator on my 350 and rubbed in the marks, transferred that to customer motor indicator lining up the zero marks so I would know where it actually was set. It was a lot of timing, I took just a smidge more out. Anyway, that fixed it, slam dunk on the tune, the motor ran like a race motor, snappy, pulled hard, tested good, didn’t want to break anything. Very happy customer when he left. A rare problem but I have run into that type thing a few times now so hopefully that may help someone with a stumble.
Thunderhead 289 has a couple videos on carb and distributor tuning that can really help.
He actually makes the best videos about that but he's new school...odd
So much gold in this one video! What solved my issue was using a quality rebuild kit. The rubber on the auto parts store accelerator pumps is crap and as soon as I had a good pump in the carb it was fine.
One of my favorite sources of info for chevrolet cars was the book put out by the factory on performance upgrades and tuning for chev 4 cylinder and V8s.
If your accelerater pump and carb are working correctly, but rich. The rich condition is fouling plugs slightly. Go to a hotter plug to fix stumble.
Don’t forget about a weak EGR valve. If spring is weak, valve will just pop open and cause a lean mixture. Just unplug EGR and test drive vehicle. If it goes away, just leave it unplugged or replace it.
In queens we used to get a guy in the car put it in drive with the break smashed down, the guy under the hood would turn the distributor until the the tires started to break traction. Lock it down and your ready to go.
@jerryakbar6147 lol.. old skool stuff is still viable. Maybe not "right" but can get you in the ballpark. Cool story jerry
@jerryakbar6147 another old redneck way... is listen to the engine at idle. If it's hitting correctly, (just under the rattle sound). Just rev it to 2500 ish.. turn it back and forth until happy.. adjust depending on application. That will make it run. Not correct.. but a good base point. Until fuels change of course. Lol
Timing curve , fuel curve . Wether it's analog or EFI it has to work properly. Your timing has to move as fast as the fuel curve. I learned the hard way but it's the best way to learn.
Simply thanks Tony for videos like that!
My 66 Dodge Dart had a bad stumble in sub-zero temps. So I fabricated an exhaust manifold shroud then connected it to the air cleaner with a flex tube. It fit perfectly into the snout just by chance!
Thank you. This is what I visit your channel for. Older mechanics looking out for younger mechanics is what our culture is about. Younger mechanics have an interest in older tech with less electronics. Plus it's awesome seeing and old car or truck still on the road.
Thank-you UT, good info, love the old school stuff …. Cheers! 🛠️
I am sure this video helped a lot of people, Tony.
Tony. The GM rigs pull timing with vacuum. When the vacuum drops they advance.
Is that manifold vacuum?
@SchoolforHackers Yes.
Another good video. Watching your videos brings back memories of problems I encountered years ago as well as what I found was the solution to those problems.
Thank you Uncle Tony, I have been waiting for you to post some hands on wisdom I can learn from. I'm sorry, I just don't enjoy the "chat" sessions.
Uncle Tony giving me the confidence I need to tackle my first classic car project. Wish I knew some of this stuff years ago. Thanks TONY!
I haven't had a carbureted engine in decades. But hopefully soon I'll get back to basics. I'll definitely need this information
Gonna work on the 78 Z28 tomorrow. See if i can get this stumble gone
Wow, been so long I almost forgot I knew this stuff!
Love your vids Tony I am learning hot rod knowledge from you keep up the great work thanks bro
I don't have any stumble, bog or any other troubles. But tuning has always interested me, so you got a view. You just reminded me that I haven't really finished the setup on the Edelbrock AVS2 that came on my SBC. Might be able to do some timed runs and get the jetting right. Once it's there I can see how it does using your power timing move. I have always just gone 34 to 36 degrees all-in on my 350's cause it's safe and works. I suppose I should be trying to get all the juice out of my car. Otherwise I'm leaving power (fun) on the table.
Very useful. Now I have to figure out what type of carb and vacuum system my Fiat 600 has.
On Ford pushrod engine, I attach a piece of stiff wire,bent to dist side,near the Dist. Mark dist with white marker. Make fine adj roadside by moving dist.
I used to find seized up centrifugal advance weights and stuck power valves in carbs on old cars as well. They both have to move freely.
I had a customer with a 78 Monte Carlo w/ 305 V8. Complaint was a major lack of power. It would have good throttle response, but then it barely had any power at all. It had all the symptoms of a plugged cat converter. After replacing the cat and not solving any problems I discovered that the centrifugal advance was totally stuck. Removing the distributor and freeing up the weights made it run like new! Why did it still have some pep off the line? The *ported* vacuum advance gave just enough timing to take off, but as you opened the throttle more, that vacuum dropped off, and timing was back to where it was at idle. I learned quite a bit about timing after that!
BTW, I have always used the "advance til it pings and then back it off" method, with rarely any problems. Glad I didn't try that on the Monte!
(Zero lash )in-between the accelerator pump screw & arm
This worked for me -- on a boat 351W -A vacuum gauge reading of 20 in. Hg Edelbrock 1409 Carburetor Step-Up Springs--stock was orange springs with bog than changed to the silver springs=8" bog gone
When I switched out my edlebrock 800 avs 2 carb to a Holley XP 750 I also needed more advance timing
I experienced this with a slightly modified 360ci FE engine. and fought it for quite some time. the engine was bored .030 over stock with a 539 lift 280° duration camshaft. with four barrel intake manifold and carburetor. I tried multiple carburetors and distributors but still had a lean condition issue. where it would cough up though the carburetor. and on Fords ported vacuum is used with automatic transmissios. and manifold vacuum is used on manual transmissios. and this vehicle had a manual transmission. I finally found that it was because I had a speadbore carburetor. using an adapter on a straight bore manifold. and the back cylinders would lean out because the primary throttle plates couldn't feed the rear most cylinders. because of the straight bore manifold.
I've gotten turned around on tuning cars with accelerator pump problems it's just like the mechanism in a spray bottle like Any kind of spray bottle like Cleaning products windex come in or any kind of just bottle you fill with whatever same kind of mechanism If you pull the trigger you don't have a good solid squirt. I was always taught that it should be a clean spray throughout the throttle movement not A Half Squirt and then a dribble. Also need to make sure that the fuel bowl is full when you're checking this cause you cant do it a bunch of times and get yourself turned around because there's no more fuel in the bowl than the engines flooded and it won't start but anyway I hope you get my point I love this video Tony. This is the kind of stuff. That was lost in the generations after you.
#1 Best Channel on TH-cam
20:07. While yes I agree.. it also made sure the distributors vacuum advance functions were all working correctly. If you did all this and still had issues.. put a timing light back on it with the advance hooked up and rev it up a little to make sure.. basic stuff to us.. but thought I'd share just incase.
Great explanation, Thanks
Bad points gap can really mess up the spark timing, I have learned the hard way.
A small amount of point gap error can cause the spark to come far too early, or far too late, and really mess up your timing!
Uncle Tony…today’s shop teacher…Awesome & informative video UT, Thanks!!!
Hey Tony, I totally agree with you on dial back timing lights. I have a Craftsman timing light from the 80s that I've had for years that I bought, that is the dial back style and I found it not being accurate at all so I took it apart and bypassed (removed the pot/dial). After that it works perfect and still does today. You just can't beat the old tools as long as you know how to use them. Later
Hey Toni. It‘s always good to have a look at your clips. Would like t thank you that.
So I’m a slant driver from Germany.
Keep on doing that clips.👍🏻
A full advance ignition is my choice for performance. Never had any luck with the Vac.
The problem I see with setting initial timing by vacuum or by ear is it doesn't take total timing into account. Distributor mechanical advance amount are all over the place with OEM distributors. Most times you'll find 15 degrees or so runs really nice at idle. If that distributor was set up originally for a couple degrees advance, it'll be way over once the rpms come up. If the original spec was 2.5 degrees ATDC like my 68 D200's 318 it's WAY over. Jump to my 81 W250 with a 318 auto the fender tag says 15 BTDC factory spec. Same basic engines, vastly different amounts of built in mechanical advance!
So I never recommend those methods unless you check the all in mechanical. Best bet, find the initial and all in it wants, mod the distributor to match.
Wasn't 35 degrees total timing advance the rule of thumb for stock engines?
@Joetechlincolns Somewhere around 35ish, but that's not carved in stone! Bore size, compression, combustion chamber design, fuel octane all play into it, plus, whether its naturally aspirated or force fed.
That's why efi is so good it made timing computer control but people only mention the fuel delivery of efi. Noobs
Great Info. I'm getting ready to start a new (to me) engine. I'll be watching multiple times to get the timing and Carb set.
Terrific! Thanks Unko!!
FANTASTIC video, thanks!
You forgot the off-idle circuit. Off -idle slots transition the carb from idle to main metering. Some early 70s two barrel GM carbs had a screw in the back of the carb under a plug that you were not supposed to remove. They were often set too lean and would cause an off-idle stumble before the accelerator pump had a chance to work. They were called “off-idle air screws” so turning them in richened the off-idle mixture.
great stuff thanks. when you are setting up TDC and adjusting by hand, remove your spark plugs so that you are not fighting compression (especially turning reverse when using the damper bolt),
The timing situation assumes your distributor gear and cam gear are in good shape and limited backlash. Older cars really need that examined and fixed as needed.
Nice break down, how it will works.
I had a problem with an edelbrock carb that was new . It had a bog I did everything to it. It turned out the thermostat temp was way to low no fuel atomization
How much risk is involved with the spark knock technique regarding potential engine damage?
carb idle set to a square idle transfer slot also helps if theyve been monkeying with idle screw
With power timing listening for spark knock. Is that done with vacuume advance pod hooked up?
Well UTG talked me into getting a g body. Said if he wasn't Mopar guy that's all he'd have. Just bought 83 olds toronado. Has a carb and a thousand vacuum lines. Guessing I will be watching lots of his videos know.
Good news! Once you get it running right, all those vacuum lines will be in your trash can
What’s your opinion on setting timing on a ported setup, then switching to manifold vacuum? It seems to help start easily and then have lots of timing down low without too much up top. Like a recurve kinda, with better starting possibly. I’m running that on my L20b for now.
Great, great, great. Thank you.
Ol Carter BBD! My 73 318 Charger got 22.5mpg
Would love you to cover locking out distributors and timing on big cams, ignition and carb tuning. Ive onluy got 5" vacuum at best idling and even a 25 power valve is borederline. Im current running a locked out dizzy set at 40 degrees. That seems to be where it want to be from idle to top end, ut just works great, Any more and it starts to detonate and any less it wont idle!
What about the tranfer slots being uncovered by haveing the throttle blades open to far at idel
You should look up the Chrysler Australia engine design plans for the mid 1970s , Chrysler Australia wanted bigger engines , GM Holden was going to import 403 ci Oldsmobile V8s for its Statesman long wheel base model and LE Monaro two door, Ford wanted the 400 V8 that it was going to use the low deck 302/351 Cleveland block it already cast at the Geelong Casting Centre and install a 4.0 inch stroke crank. So Chrysler Australia was looking to jump on the 400 ci band wagon , but a big block B400 was out of the question , so Chrysler was already casting the 215/245 and 265 ci Hemi Six here ( that they also wanted enlarged to 300 ci ) so the plans were drawn up for a 404ci LA based small block . The official Chrysler Australia paperwork listed a 4.10 bore Block Cast in Australia and 3.825 Stroke crank of nodular iron also cast in Australia , with 6 inch rods and pistons to match, the project called for a 6.7 litre V8 for the late 1970s beating Ford and Holden . Several 4.10 bore blocks were cast and one engine assembled . No idea were it is today or if it ever ran . But it's an interesting piece of Chrysler's history , a 6.7 Or 404 ci LA based Small Block Chrysler would have been amazing . All the LA after market parts such as intakes and cams would have fitted , plus a 6.7 litre SB is so much lighter than a B400 . Shame Chrysler Australia never proceed with that engine .
Muscle Car Solutions also has excellent deep dive videos on carbs and timing as well... great stuff..
i was born in 82 so most of my driving/adult life society has been injection.... although my dad was a old hotrodder.....mom always had a newer car bud dad stuck to the older stuff from the early 70s and older.....i learned carb adjustment and points dwell way before i was old enough to drive....my firts car was a 49 willys wagon whn i was 14....now im in my 40s and prerty much only drive stuff from the mid 60s and back......now my kids are building classics too.....its wonderful passing this info to the next generation....if we dont its gonna be lost
Always set with a cheap neon timing light. Didn’t know about the difference between ported and manifold vacuum. I also used static timing setting it with a cigarette paper like one does on a motorbike. In retrospect I think I got good results timing my various 60s Chrysler cars but may not have got the GM cars timed right. My 63 383 would chirp the tires shifting from 2nd to 3rd at 85 and that good enough for me. I discovered those cheap timing lights were an excellent was to diagnose a weak or intermittent coil because they relied on the coil for power. Aimed at the firewall you could see when the light wasn’t consistent. Intermittent = bad coil.
How about deccel stall, don't think it's the secondaries spilling out the vent.
lol, I wish I knew more bout engine tuning, more specifically timing in the 80’s driving old $200 dollar beaters. We would never dare stray from the factory recommended settings.
Good info.
Great explanation
There was a third way to set the timing on car’s with a vacuum advanced distributor, but it did not always produce what I’d call a reliable result. And that was to disconnect the vacuum advance, block off the vacuum line and loosen the distributor locking bolt just enough to move it by hand with the engine running if you had a distributor wrench. Then rev the engine without touching the distributor, and when the distributor moved lock it in place and let it return to idle. The reason I say it did not always produce reliable results, was it could be difficult to get the distributor locked in place before letting the engine return to idle or have the distributor locking bolt loose enough for the distributor to move on its own. Or still have the distributor locking bolt tight enough, to lock the distributor down while holding the throttle at a fast idle in a single twist of the distributor locking bolt. I played with that method of adjusting the distributor in that manner a few times, and the results could be very interesting and sometimes wildly inaccurate. My dad had a strobing timing like that did not have that dial, and it was very accurate as long as the harmonic balancer was in good condition and the correct one for that engine. And had the timing marks in the correct location on the timing chain cover. If not, I had to go buy timing tape, to clock it at TDC.