The Myths And Realities Of Carburetor Sizing- History Proves The Formulas Don't Work
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- เผยแพร่เมื่อ 6 ต.ค. 2022
- Calculating cubic inches and volumetric efficiency to arrive at the correct carburetor size for any given engine combination seems like a reasonable way to go about things, and is ok when dealing with a completely stock engine, but when you start trying to make real power, it will leave you wanting a bunch more.
Here's a rundown of some of the factors at play, how the manufacturers chose carb packages, and a few basic guidelines that will get you going in the right direction.
#Holley #edelbrock #classiccar
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Did anybody else look at the Holley carburetor on the left side of the screen and wonder why the bolt for the air cleaner was so long? Then I realized there's a jack back there that's just lined up perfect LOL
Same lmao
Yeah, me, too.
Yeah my old 47 yo eye are .....weall just say I need to eat ton of carrots 🥕 😅
As a young hot rodder I love this kind of video! I would love to hear your just tell stories about the old days of hot rodding and what it was like. The history is so interesting to me!
If you haven't you should watch his video on street racing in NY during the 70s
I use to run with the Street Racers while "Big Willie " was president . This man was directly responsible, with some others for bringing drag straps into California.
As for me, I saw the closing night of the original Lions drag strip. I was there for the opening night of the new Lions, and I raced the last night of that venue.
There's a story for you.
@@raiderjohnthemadbomber8666 very cool sir! Hopefully we get another venue here in California soon instead of the irwindale 1/8 mile
@@KJ_Moore
Yeah, I hope so too, even though I don't live there anymore. So anyway, I've also visited and raced at Irwindale and OCIR, which had powered rollers in the staging area for anything without a starter. But Lions was my home turf, as it were. Good luck with whatever you're building. Currently I'm running a 74 Nova with the original small block. I've managed to get 536 hp out of it. It runs high 5s in an eighth. This'll probably be my last hot rod build. I'm hoping to get two more things built before my body refuses to help me. It and I are currently having creative differences. Hey, what are ya gonna do?
@@barneymiller7894 11
NEVER worry about your videos being too long. I appreciate your time and sharing your wealth of knowledge. There is a saturation point on learning. I bet some of the people who dropped off come back and watch this video again..and again!
Years ago I had a auto shop and also specialized in high performance tuning for street cars and drag racing. A good example: one customer had an 86 Monte Carlo SS that he drag raced. He didn't have the budget for an engine so we kept the 305, ported the heads, swapped the cam, installed an old Torquer single plane intake and a Holley 850. Everyone told me I was nuts it would not work. We proved them wrong! The engine was run up to 7300 RPM at the track and worked great. (Until the stock bottom end let go) Then I gave him a built 327 I had laying around.
I’ve got a 305 in my Grand Prix (Monte Carlo with some more chrome) and people underestimate them. They’re not power houses, but with a few mods they can be made into formidable motors. I want to do cam and heads soon, but I’ve got a lot of projects right now.
In the late 80s my buddy had a 79 Mercury Capri. We built a 2.3 Ford 4 cylinder rubber band motor.Punched .040, 10.5 :1 TRW forged pistons, ported the Hell out of the head, nasty Melling cam, home-made single plane intake with a 430 cfm Holley 4bbl, Ford Motorsports catalog header and flywheel, with a 4 speed. We went through allot of clutches. We stood it on the back tires regularly on slicks.
You saw daylight underneath the front tires with what sounds like a 210 crank hp manual 4 speed Fox? Really? Did it ever break out of the 13s?
Yup we have built a few for dirt cars, they are surprisingly decent
Thats awesome! I'm thinking about building a 2.3 for my '65 Falcon! It's currently got a 200 six in it but I estimate the 2.3 would give me even more room under the hood and save on weight! And there seems to be more aftermarket support for the 2.3!
@@jaylestingi5418 Troll.
The 200 is just a sad motor unless you're ready to pick up parts from Australia. They build some screamers out of 200's down there. The 2.3 still has such a following that the go fast parts are out there. Be a screamer in a Falcon.
12:38 - “What did I do, I broke it!?” This reaction, and result, is a big reason I like your work. Genuine AND reasonable reactions to twists and turns. Exciting things happen and it’s no worse than you grabbed a cold coffee versus a hot coffee… Just drink it and plan better next time. Perfectly and perfect.
My brother had one of those 2.0 Pinto engines in his Mk. III Ford Cortina - with just a cam and a DCOE Weber it would rev to 8k. Made for an amazingly quick car despite the perceived lack of cubes. 👍
I talked to Norm many times about the beginnings of his racing. The first car to actually have his name on it was a customer’s car, it was a super stock dodge that ran indoors at the amphitheater. He put the name on the car in return for spark plugs and tune up parts for that same reason. The “mr norm” name wasn’t painted on there, it was on a cardboard sheet. Soon after norm had his own team who later on ended up becoming the chi town hustlers. Oh, there’s a pic of that car online showing it running inside at the amphitheater.
I had some very interesting conversations with Norm back in the 90's. Did a five page feature on him for Super Stock magazine back around that time.
@@UncleTonysGarage I have that article. Many awesome conversations were had as we drove hours to car shows, I learned a lot from him that I will never forget. The best stories were from the days of match racing the 65 AFX car that he acquired from Roger Lindamood. He purchased the butch leal AFX car and was going to run two AFX cars, sadly it was crashed in epic fashion. Funny what can happen when creativity gets involved with young car guys in the late 50s/early 60s out of their dads gas station…
Fords cross Boss for the 302C, the 406 Tri-power, they had 3 350s, put a pair of 500s on the front and rear they make 425 hp they claim the 427 made, if you replaced the 2x4, on the 427 LR, put a pair of 750s on it. 500 hp instantly . OT/Pull on the choke lock Carters do that
One of the reasons I like Quadrajets is the ability to tune the secondary air valves and metering rods for maximum performance and use the primary side for driveability and economy. It does need a cut down, dropped float for sustained high rpm or it will starve.
I love Q-Jets. I developed a conversion to make early models dual feed. It works only at wide open throttle using a solenoid from a Nitrous kit and a throttle activated switch. I have a cust with a 540 BBC in a 70 Pro Street Camaro that has gone 8.80's with it.
I started with a 500 Caddy main body & airhorn which flow 1bout 900 CFM.
I lobbied NHRA & IHRA to make it legal but the politics play into it and they won't allow it.......some slick guy could possibly hide it if he was clever, but the float bowl capacity is the drawback........
I actually have a better way to control the air valve.......starting doing this in the 70's.
Use a long air cleaner stud and locate a spring appox .500 inside diameter that will fit over the air cleaner boss and sit on the hanger. I use ones that have about the same tension as a pump return spring........anywhere from an inch or so as long as it fits the air cleaner.
Put a 1/4 washer on the spring and I use a snug fitting wingnut. Loosen the stock air valve tension so the valve is really floopy but does return on it's own. Put some tension on the new spring and try it. You can now adjust it without playing with the stock hit or miss stock system.
Some Q-Jets I have to modify the air cleaner boss so the spring doesn't bind, but I do this on any car where tuneability is key. You'd be shocked at how well it works. I use a drop of Locktite red so the stud doesn't move.........
I'm using a Quadrajet as a blow through carb on a turbo'd 5.7 Vortec and it works great.
@@quietcool4884 we need to see a video of that! There were no cheap handy cams back in 1985 when I did mine.
Had me ah robchester quadrajunk once. Made a killer trot line weight🤯
I grew up watching quadra Jet carburetors cycle across my father’s work bench.
He worked for the railroad following several years as a mechanic with both GM and Chrysler.
He loved those carburetors. I don’t know how many people that would praise him for getting their fuel mileage back.
Several of his old drag racing friends that were still in the game would pass through town every year or so. That was always fun.
I remember several instances of them trying things with these carburetors through the years. As a kid I would just begin to think I had a basic grasp of what was going on with them, then I would see these experiments.
Some worked others not.
I’ve tried my hand at building a few. I could get mileage out of them at best mostly sealing the metering wells.
I’d ask my father what to do when I had rebuilt one. His answer was always the same. “Keep screwing with it until you understand there is no magic wand for these items.”
I just never had the patience to mess with them for very long or he would get tired of watching my frustrations and take over. By then I was spent. I never remember it taking him more than a few minutes to straighten out what I had done.
I’ve seen him and many knowledgeable carburetor tuners get into fights with various carbs of other types. Just don’t remember too many with these men and Quadra jets. Sure there were some worn throttle shafts that they were tooled up to repair back then but they could quickly identify that even I could.
One thing is for sure. It takes patience and tenacity to use a carburetor effectively.
I recently bought an old 4500 dominator 750 cfm.
Dad marveled over the 750. Sat down and took it apart and gave me a list of parts to order and told me to get it cleaned up and ready.
Damn if that wasn’t expensive……. Still yet it’s been fun to sit and visit with him over it.
I hope to have the patience now. I’m 52 dad is 77 and still getting up every day looking for something to get into.
Rough tough and gruff. There’s no doubt that instant gratification has taken its toll on my father’s posterity. Mine as well.
I feel like my life isn’t going to be quite complete until I learn how to be patient and correctly tune a carburetor.
I took an 87 Olds Cutlass Supreme with a 3.8 Buick V6 and a TH 220 tranny, up graded to an Edelbrock Performer setup with a 600 cfm, TH200R4 2200 rpm stall lockup converter and made it streetable (broke motor mounts every 3 months) and got it to give 30 mph. there were other mods but you are so right in that we threw away the formulas and went with our gut feelings for what was wanted. Please keep teaching this younger generation about what is really going on and less techno-junk, formula junk. Ah, for the fun of the 60's and 70's!
Here's my take on the formulae used by the aftermarket to determine the recommended CFM for their customers: The manufacturers grossly undersize the recommendation for the sole purpose of reducing warranty replacements. That's it in a nutshell. An undersized carb will perform well and the customer will be happy and won't wish to return the carburetor to the manufacturer with a scalding message attached to it or (in this day and age) post on the interweb how crappy the carb is.
Your wisdom, knowledge and ability to explain the depth of the the physics behind making something run is astounding.I am super appreciative of everything you've shared and look forward to everything else you will share with us. I look very much forward to more of the carburetor talk
Every time Tony starts talking about stuff like this I want to go out and start my 67 Impala SS just to play with the accelerator !
Recently found Tony 's channel and I'm quickly becoming addicted to watching every video! Endless amount of knowledge and no BS
I really enjoying when you talking about carburetors, I can watch you talking for hours because you really know what are you talking about!! Please do more of those carb videos cause there are many useful small information on these videos that makes huge changes on performance engines.
I would like to hear more about mechanical and vacuum secondaries and when to use them.
@@jonathanlawson4667
Also to add to our comment- I grew up being told by alot of racers, mechanical 2nds are better w standards. Vacuum 2nds better w automatic
Vacuum secondaries don't work well with a manual transmission because the throttle action is off/on/off/on much faster than the secondaries can actuate.
Why not stick with mechanical secondaries and drive with your foot, forget a vacuum secondary.
Also, an air door like you'll find on a quadrajet, isn't a vacuum secondary.
Vac 2nd... never use em!
Always use a mechanical carb ! If performance is your goal
Its often a matter of preference. On a dual plane manifold you can often get away with an 800+ carb with vacuum secondary or an air flap etc.. even on a moderate engine, these manifolds often show extra power when you increase the carb size. But with a single plane you might not find extra power using a large carb even if you are making more top end power than you could make with the dual plane, they often dont see gains from makking the holes bigger than they need to be. and as long as the transmission agrees the "right" carb might not need to be vacuum secondary. That's not to say you cant use a sensible mechanical carb on a dual plane or a vacuum secondary on a single plane to improve drivability a little. It sounds backwards that youd use a bigger carb on a less powerful engine and a smaller carb on a high revving engine but the manifold designs respond very different and have different pulse energy. And you may be more inclined to use the low speed power of the dual plane wanting the vacuum secondary there to help out if you floor it with a tight converter and a governor that doesn't encourage it to stay in a lower gear long enough or you just don't feel like downshifting and short shift as you cruise. But if you like the engine rev happy and your trans is tuned or you manually shft accordingly you may not feel you need vacuum secondary and may want the instant input of the mechanical carb.
I for one, can never get enough of your carb videos. Keep it up.
Awesome real word info, me and my brother have been tinkering with hot rods all are lives, every time i watch a video from UTG i learn something new.
Makes tons of sense and I guess would explain somewhat the performance of modern cars. Because they can build huge CFM capability into the intake tract and the computer makes it work in all conditions.
I run the factory numbered Thermoquad on a stock 340 with headers. Max flow on the small block Thermoquad is around 800cfm, sounds like a lot but the carb only gives the motor what it needs. That's the beauty of vacuum secondaries.
Same carb I have on my big block, runs fantastic!
And it's not vacuum secondaries, it's an air door like a quadrajet. Punch it WOT, all the butterflies are open no matter where vacuum is. The air door does the compensation for secondary transition.
Thank you for this video!! Awesome information. This is hands down the best channel on TH-cam.
An easy way to tell if you have too small of a carb is when your floor it and both secondaries are open and your still pulling a vacuum ( typically with a vacuum gauge routed in the vehicle) of 1 or 2 inches of vacuum or more you know is a good indication of a carb that’s too small!
If you have 1 inch of vacuum at the top of the rev range with 0 in the mid rev range you have the right size carburetor. Thats for the street use in my opinion. Always better to go smaller than bigger on the road
1 inch is fine, ya need some vacuum. If 3 or 4 inches, feel free to go up in size.
Good point.
First of all thank you for all of your knowledge. I am a Chevy guy but I watch all of your videos religiously! I agree with this video totally. I bought a new 950 holley xp for a 60 over 396. People were saying it was too much but it ran great. My argument was that the engine is only going to use what it needs and if I upgrade cubic inches later on I will be 👍
There is some truth to the engines only uses what it needs carbs depend on the signal from the engine and oversize too much you lose signal which effects driveability.
These videos are so informative!! I have a 1968 LA318 with intake and 650 CFM Holley double pumper mechanical secondary and it responds beautifully!!
I love your videos man, grew up workin on cars with my dad and grandpa and now I have my own classic cars that I love working on. All this knowledge is golden and unfortunately being lost. Thank you for passing it on to the newer generation with your videos!
Great vid! Built a 327 ('67-2 bolt mains) chev in 1975 , ported it like you do, 325hp corvette cam, lifters,valve springs. I used a Holley - double pumper Spreadbore and "Doug Thorley" headers. All shoved into a '59 Chev fleetside. Awesome power!, Sun Machines "dynoed" it at 364hp on a portable dyno at our College. I chose the 650 Spreadbore by 2 x the cubic inces. This helped a lot of my friends decide on their CFMs, too. When you use the veh. for cruising and the "Occasional" stoplight race, THIS is the best formula. Thanks, Tony!
Thanks Uncle Tony. I learned something today. Great video. Thanks for sharing.
Thanks Uncle Tony! Everybody says to go low with CFM but you bring up some great points that are indisputable facts. You helped me to make up my mind and dump my 750 dp for an AED Performance 1000 HO on my 496.
I always like when you do these type of videos, I don't care if it's a longer video.. I don't really think about the time.. I like longer videos personally.. It's not really the length but as long as the content is valuble.. The time steps to the side.. Or entertaining.. Sometimes I am in a hurry but I always will get to the video later.. At least your videos.. Hopefully you and Al are doing ok.. He took it pretty hard on that car.. Poor Al.. Lol.. He spent so much time on it.. He is a good guy.. I think he let the comments set him off too much tho.. You are gonna have na- sayers.. Life goes on and most of us appreciate.. It is easy to get upset as a viewer in that the suspense leading up to it and this car is sorta personal to us too.. I was pissed at first about Slaghammer but I quickly realized, dude, how you think they feel and it's not even my vehicle.. Lol.. But I was like, Damn it.. Then after a minute I calmed down and felt bad about tbe situation.. And you know, Over all, Al and you guys kicked ass! Made Power Tour, a few runs and then some trouble.. But it happens and in my mind you guy accomplished a mile stone with that car.. It was a crappy 4 door carcus not very long ago.. So I don't care what anyone says, Al kicked ass on that car after working all day and his days off and the man isn't exactly a spring chicken so to have that dedication is remarkable.. You guys need to go have some fun and blow off some steam or something.. Not that you are fighting, idk bout tht, but have a holliday somewhere fun.. Go race go karts or something..lol.. Love you guys! ✌
Thank you
Ditto, great video and great way of explaining it, Uncle Tony. It could have gone even longer and I would still be listening. 👍🏼👍🏼👍🏼
@@UncleTonysGarage Speaking of Power Tour, Thunderhead289 was there with his AMAZING! 45 MPG! V8 Maverick. The problem is it can barely reach highway speeds. He 3D printed an intake to mount up a lawnmower carb, added a home made, electronic air bleeder to continuously tune mixture, and 45 mpgs!
I have trouble understanding it, but I think he also advanced the timing to take advantage of the continuous vacuum, so maybe tons of vacuum advance could combine his mileage with some power? Or should he, or I, try to make another manifold to bolt a big carb up in addition to the lawnmower carb and a staged throttle linkage? or bolt his mower manifold to a dual quad manifold? I think, however, that he would have to then replace his advanced base timing with vacuum advance anyway.
So can anyone out there help me understand his amazing results so we can then use that understanding to combine those results with more normal power? or even high power?
@@alan6832 I think if you restrict the power output of the engine that much, and do it efficiently, those kind of mileage numbers are going to be achievable no matter how you do it. That's the only reason it worked. If you changed the setup for a "power on demand" with a separate carb and everything, it would end up being the same as just running something like spread bore or an EFI setup. Only way you get 45 mpg out of that is to keep your foot out of it. This is not to mention that his test was all highway miles on flat ground. Most well-tuned engines will have surprisingly high cruising mpg. It's the acceleration events that use all of it. With thunderhead289's limited testing, not only was it highway miles, he also made it impossible to use a lot of fuel under acceleration. Hope that makes sense.
Excellent, thanks. I saw this with two-stroke dirt bike engines, in the 1970s. In about ~1974, a stock 125cc motocross engine might come with a 26mm or maybe a 28mm carb. Then, one of the mags did an article about a tuner who was putting _huge_ carbs on them, like 36mm or 38mm -- bigger than the mightiest factory 400cc+ bikes! Everyone said, _This thing shouldn't even start..._
But it worked really well for racing and high-performance operation. Power, response, area under the curve, the whole thing. The factories started putting far bigger carbs on their hottest engines almost immediately. It swept the industry in basically one design cycle. Wish I could remember the tuner guy's name.
Uncle Tony, with the weighted air door on the secondaries on the Edelbrock carburetor, it has to be sitting in the normal position to function the throttle linkage. If you hold the carb on its side the weight counterbalance moves into a position where the throttle cannot go wide open.
Tony, I always wondered about that! In the 70's I had a 340 Cuda drag only that ran high 11's. I had a tarantula manifold,12.2:1 compression, .501 lift cam with a holley 850 double pumper. I bought a holley carburetor book and doing the formulas it said I should have a 650 CFM carburetor on it. So I sold the 850 and put a 650 on it. Brougher's speed shop told me that was a big mistake. I should have listened to them, it was! Thanks for finally explaining that and holley should have never put that in their performance carburetor book!
Some day someone explain to me what a "tarantula" manifold is.
So i had to finish the vid, and ur "Double the cubes" formula is WAY better than the others, like how my 950 is workin great on my 462......just had to add.....GREAT stuff my brother!!
😊 the world needs more uncle tony. Awesome information. You explain it sooooo good.
This episode was like waking up on Saturday morning and watching Kroft cartoon super hour back in the 70's. Great content and information Tone!!!
The highest quality guidance is completely appreciated your experience is hands-on and tremendous.
Lol, I actually had a 71 stock Pinto and ran a Holley 600 vacuum secondary on it. Surprisingly it ran pretty good! I also ran a 2X4 tunnel ram on a SBC in an Olds 442. It was mildly modified but the throttle response was incredible!
Many years back, I'm thinking about1978-79, I built a 318, Edelbrock LD-4B, milled the heads, headers, 268*/.450" cam, cool stuff. I got a great price, $80 on a new Thermoquad from Direct Connection. Got the spreadbore adapter. But it would bog big time off the line. Thought it was too big for the engine. Traded it off for a used AFB which I rebuilt. No bog, but I could tell I had lost power in the mid to high RPM range. I did not know at that time how to adjust the air valve on a Thermoquad. Those were the days of no internet, and I didn't have a clue how to find out, or what was really the cause of the bog. I know now the Thermoquad was used successfully on 318's, without the bog, even though it was somewhat larger CFM than the AFB. Live and learn.
I had a built 355 68' Camaro Street/Strip. I tried a 750 and it didn't work. I didn't know a lot and It had a stock converter. The wife had to drive it to work every day and I needed it to run good for her too. So I went to Super Shops and bought a new 600 vac secondaries Holly. The thing ran like a dream out of the box. No top end though. So I put a Nos plate under that 600 for when I would go race people. Tires were shit back then. It would launch great on the 600 but white smoke if I left on the squeeze. I had to wait till 2nd engaged to hit the NOS. My point is, you have to consider the converter also. And the rear gear ratio. Along with the weight. Auto or manual. Even tire size. I kick myself in the ass all the time for selling that car so I could buy the New GSXR that just came out a year or so before. A little cam advance and I never lost a race on that thing. It was lightyears ahead of anything else that was out in 87/88 whenever it was. Then i had no remorse. Now I wish I had that Camaro.
Absolutely perfect answer to the classic too big vs too small - Chevy vs Ford age old arguments. I couldn't have explained it better!
I always went by airflow. The more airflow you have front carb to rear exhaust, This will give you the most power. Hence the bigger carb. I run a 750 Holley double pumper 4 corner idle on a stock Chevy 350 with a mild cam stock heads 2 inch headers to a 3 inch collector with 3 inch pipes to 3 inch in and out mufflers and this motor runs like crazy.
Great piece of wisdom. I didn’t drop off. Thanks for the great memories..,yours and mine!
Great video. I had a turbo Buick 3.8 in a Chevy Luv, and installed a large carb off a ~'70 buick 455. I was universally informed that it would run poorly and be difficult to drive and wouldn't really help the performance. Initially drivability was poor but with plenty of tinkering, it became very drivable and smooth for normal use, and perceived significant torque increase at very high RPM. Generally I had to get the very low flow mixture dialed in for normal drivability, and elevated fuel flow for the secondaries (no intercooler on that engine). The biggest problem I had was wastegate over-ride and resulting detonation, which took some gas pedal skill to manage.
Awesome video!!! I can't get enough carb videos!!!
built a 454 chevy and put in a 1976 camaro. tunnel ram and 2 street brawler 600 cfm... dumped fuel.....first oil change was 90 %gas down jetted 2 X and finally got it , the timing and valves right.. have to have an 1100 idle so as not to be so rich at idle have a 700r4 and at cruise she runs great well at all levels she runs great but she wants to run plain and simple. great video wish i would have seen this before hand. she runs like a dream with all sweat and tears an struggles great videos watch all of them and learn alot all you do is helpful on all makes!!! keep rolling!! ill keep watching!!!
I like to experiment.My trailer-dragging,junkyard hoisting Dawg has a mild 390,headers,electronic ignition,C6,3.73 gears, and a big honking tunnel ram with a pair of 500 cfm 2 barrels.Gets 22 mpg.Got 16 with a '75 Mercury sled on the trailer.Up next,2 32/36 Holleys on my 200 six
That helped much - thanks again, Uncle Tony!
I never claimed to know Tenth of what Tony has provided me with since I subscribed.
You sir are "The Man".
I raced a 1967 Mustang with a Factory 289 and factory 4 barrel intake. 4150 if I remember right. That car ran like a banshee and ate a lot of small blocks' lunch.
I made a decent living off my wins on 2 lane back road raceways. Small tuning on that factory carb was priceless.
Thanks for the knowledge Uncle Tony!!!
American carburetors have always been a mystery to me. The SU carburetor is the only carburetor system that made sense.
Your videos have really helped me get a better understanding of downdraft carburetors and their functions. It’s understandable how so many great mechanics still struggle with proper sizing and tuning.
Im still clueless. But I feel a little more comfortable after watching each of videos.
Keep ‘em coming!
Amusing. SU carburetors are universally mocked for their ineffective dribbling performance. But for tiny engines with no power, they are fine.
@@oldmusher depends on the SU Size. 50mm + SU’s are pretty darn awesome. The beauty of the SU Carb is they can tuned to provide optimal performance across the entire RPM range. Where American style carbs can not.
The trick is to use the appropriate sized and quantity of SU and an intake flows well for the application.
The primary limitation is non-flow through heads used by the engines that came with SU’s.
My experience is limited to Datsun / Nissan L-Series Engines. Dyno comparisons show negligible improvement with Tripple Webbers vs tuned SU’s. The tripple webbers only outperform at the top of the RPM curve.
But ya. They’re not capable of feeding and engine greater 3.0L.
This is great info, I actually think I was close to coming to this conclusion myself when doing 'the' carb size calculation and seeing what fast cars were actually running.
Learned about this back in the day. Had an old 240z that had a few bolt ons, but the stock carbs. Ran and drove good, but wasn’t very fast. Ended up putting on a pair of Webbers with intakes I ported. Ran awesome at higher rpm, but would bog if you were to aggressive on the throttle at low rpm.
With modern stuff many engines have a much bigger throttle body than a similar engine from years ago. But, with the electric throttles the computer rolls into the throttle even if you punch it. That way it still responds good, but also doesn’t give up the high end power.
We found great success on Datsun L20Bs(approx 120 cubic inch 4 cylinder) by putting 2 barrel ADM Weber from 250 cubic inch 6 cylinder Ford Falcon, almost equates to what you said about doubling.
I had a 1300 datsun, cam in block.
780 CFM, Holley vac secondary on my 69 383 Super Bee automatic 280 Isky. Loved it, very responsive. Ramcharger hood scoop package.
Uncle Tony great videos, I enjoy watching and I have learned a lot from your videos. I was wondering if you will be doing a video on rebuilding an automatic transmission. I have seen your engine rebuilds videos. Maybe you have done an automatic transmission rebuild and I just missed it.
Very good info on all your videos , awesome stuff keep it coming
I had a somewhat rowdy 350 chevy back in the day, I used a 780 vacuum secondary holley square bore. One of my favorite street carbs once it's tuned right. Stomp the pedal through the floor and let the carb do the work.
Love the channel, so much good info! Ty Tony and miss tony.
I am running three 2 barrel holley's on top of a 351C and it works well. Drivability is good and when it's go time it revs quickly.
right now my engine is grannie tuned for gentle gas mileage. a quick carb swap makes my motorhome an overgrown chevelle SS. I only use quadrajets. My favorite carburetor since I was a teenager. My first motorhome was plagued with cooling system issues. after I had replaced the waterpump and hoses, what I thought was a blown head gasket turned out to be a cracked head. I picked up a set of heads from a performance shop at a decent price. Before I installed the heads, I ported the heads. I went as far as drilling the valve guides and making the bowls larger. I also deshrouded the valve bowls to match the diameter of the valve seats. I achieved a redline close to 6000rpms in a 350 small block chevy in a 21ft motorhome! This beast was a traffic monster. I also got into a few road rage chases where the other drivers were shocked that they couldn't get away from me! I destroyed the transmission and later had a modified rebuild on the transmission. My biggest error was that I had just a little too much timing advance and detonated the engine which snapped the crankshaft and I ruined the engine. It was still rebuildable. I didn't wreck the block. I could have done an engine swap for a few hundred bucks and been good to go again. I decided to get a bigger motorhome so I junked the 21ft. I kept the quadrajet from the 21ft and have it as a spare carb for my class A motorhome. I have tried out my 454 with the bigger carburetor setup and it performs well. But it's a pig on gas. I swapped back to the stock carb and run it gentle. I've run spread bore carburetors for over 3 decades. I used to have a couple of carburetor manuals that also showed how to change the settings and specs for track racing and drag racing. I had learned how to get the lean bog out of quadrajets and I make street sleepers that hardly anyone in this day and age even know about. I have occasionally played around with aftermarket edelbrock carburetors on other people's vehicles. But I never could make them perform in any way that ever impressed me. I have no experience with holleys or other brands of factory carburetors (I can't stand ford junk) I've stayed with the Rochester Quadrajets since I was a kid. I know these carburetors like the back of my hand. It's been my secret weapon on the streets and no square bore could even come close to it!
I agree with Tony, I have two Quadrajets on 310 cubic inches, it took some tuning but now runs fine.
nobody who wants to learn dropped off early uncle tony ,your real students stayed the whole 20 plus minutes. and thank you for the chance to learn great video
I ALWAYS GET SOMETHING FROM YOUR VIDS, YOU'VE BEEN THERE AND DONE IT, THAT'S WHY I LIKE YOUR CHANNEL.
Awsome info Unk !!!
....Just a point on the outboards on the 6pack. Compare the throttle bores on the standard 500 holley....The 6pack 500s are a 4 barrel rated
I really learned a lot from this video. I really appreciate you sharing your knowledge with us. I have a built 350 that I didn't build. I assume it's 383? It was my dad's car. Before this video, I was impressed with the 600 CFM Edelbrock that it has. After hearing what you said I believe it's starving. I just got it running and it needs to be tuned. But I think it's starving. It's a strong daily driver though. For now I'm going to say that carburetor is keeping me from blowing up the engine. Thanks again brother.
Good stuff! Could you use a vacuum gage to check wot vacuum and determine which direction to go and roughly how much?
Back in the early 90's used to run chrysler 360 2 barrel carbs on every sbc smog motor I had. I don't have any numbers but it definitely woke em up
Awesome video I swear it sounds like you have been answering the last four questions I asked about carburetors LOL right on Tony. Glad to hear all this as I ordered a 650 CFM carburetor to replace the 600 last night. Now I'm wondering if I should have went bigger lol.
Hey thanks for the info i got a 258 jeep and i got a cam intake ported head and full exauhst i got a bad off idle stumble i thought maybe it was to big running a holly 4412 maybee ill try a bigger discharge nosel i tryed everything else
Fascinating all the way through. No flies dropped off, I bet. Good topic, Tonester.
Great content 👍 what's your thoughts on the Carter thermaquad's 🤔 don't see many videos of them
Excellent video. Thank you for sharing. The cfm calculator lovers are one of the biggest reasons I left almost all of the car/tuning groups on Facebook. There’s no getting through to those people. They completely ignore the word MINIMUM and swear up and down, that the formula is to calculate the maximum carb cfm😂. I love running into those folks at the track, and watching them disappear in my rear view mirror.
Go big or go home
Hi uncle tony great video I remember those days that the mopars really ran good. I’m 74 years old I like everything back in the day with all the muscle cars 👍
Nice listening to you. You're spot on. I still love the 850 q jet. Have to meet you for a dinner sometime.
My 289 hi-po has the first centerfloat 715cfm quad. The engine loves it.
I had an old 69 cutlass with a 72 350 block and 65 330 HC heads. I put an offey dual plane low profile intake on it with 2 Rochester Quadrajets. I had a make shift dual exhaust on it as well. It had the stock economy cam. I didn't know what to expect out of it. After tuning it It just blew me away. I not only got great mileage 23mpg highway with the automatic and 25mpg with the 4spd manual but, It would just go ballistic when I opened the secondaries. The car didn't look like much but I loved it just the same. Great memories!
I have a Street Demon 625 that's going on the 318 that's going in my '82 Mirada, and a Quick Fuel Slayer 450 planned for the Slant Six in my '80. Nice to know I made choices that were perfect, or pretty close to it!
Tony is right about those formulas. Times in the past I've used those formulas. Most everything (as I recall wanted a 600 to 650 cfm) even big blocks. I like Q-jets or Thermoquads.
Love the video but need your advice please. I have a 289 Ford with 30 over with a cam. I the future I may supercharge or go with a 347 stroker. I like the edelrock vrs. What size would be best for all applications ??
I learned exactly what my problem was when you did a video on vapor lock. I was going to run an EFI or throttle body setup then I saw that video and I figured I'd stick with the big Holly. Do you think I can get that big Holly to be dependable?
I agree with the 750 carb deal on Small block for street cars if you have a little compression to with the extra cam
Great info and very useable
Thanks Tony
Love all your videos I'm wondering if there's any a carb can be too small I have a 600 cfm on a 400 sbc with a cam 10.1.3 compression I'm going through plugs like crazy
hey uncle tony, love your vids i always learn a lot and love the old school stories too...quest when you said the 440 6 had 1250cfm with the out boards being 1000 cfm each and the middle being 350 cfm would that be 1250cfm or 1350 cfm? did you say that right by saying 1250 or did you make a mistake on that i could tell you was way in that story talking bout ols school racing and dad haulin ass in the pinto lol. i get its really 975 cfm with the 3 2bbl set up but i always thought the 2 500cfm and the 1 350cfm was 1350 not 1250. thx love the vid and story im 58 and i can relate to what you say
Have upped the carburetor size on many cars I've bought used, once on a cuda 440 the previous owner installed a 600 CFM Holley ( car was slow ) first thing I installed was a used 780 I had which really wasn't big enough but still improved performance very noticable.
I had a 750 Holley with the choke housing machined off, mechanical secondaries on my big block and never could (a couple hours spent) get the two flat spots tuned out of it.
Thermoquad in it's place and off I went, it's still on there to this day.
My bone stock 66Chevy Caprice 396, 325hp absolutely LOVES the Eddy 600cfm
1406 carb. Absolutely no bog or hesitation when I slam it from a dead stop, she just eats and spins that one wheel peel on the 12 bolt, 2:73 rear gears. I had to fatten it up quite a bit, rods in the primaries, jets in the secondaries. Took about 20 minutes and didn’t spill a drop of fuel. Love those Edelbrock carbs. She’s a cruiser so it’s the perfect setup. 👍
Your combo sounds like you are correct.
Great stuff, definitely want more!
Love it. I learn so much from your videos
The best my old 305 ever ran in my '84 GMC 1500 was with a 390 Holley vacuum secondary.
I ran a 450 cfm Holley factory Ford replacement carb on a 351W for a couple of years that previously ran a 600 cfm carb tuned to application with a wideband o2 gauge. Not a damn bit of power loss between the two. Those smaller carbs definitely have their place on smaller engines and mild daily drivers, they give great response.
Thanks for the wisdom and experience
New to the channel, but lots of good info. It's getting harder to find people who know their stuff about carburetors. Lol been wanting to change carb on my 85 xj wagoneer with the 2.8l, some jack wagon installed a holley 4412 500cfm on it and I've done alot of tuning on it. It does exactly what you said about bogging down on mid acceleration. Yes I know the carb I have is used in circle track... been looking at a holley 390 4bbl with a new intake for the 4bbl, or possibly the 450cfm for the price difference. Any advice out there? Tia
Really like your carb break downs.
I agree wholeheartedly or except for one thing the day of the essentially operates as a vacuum secondary the upper air door doesn’t open until the flow dictates just like on a Quadra jet
Hi Tony,
You just brought up an old Memory from high school in the 80's. My second vehicle that I worked for and bought was a bright red 1974 Ford F 100 2 wheel drive pickup.
It was all factory and unmodified. It had a 390 4 barrel with an automatic transmission.
One of my buddies goaded me into racing him on the strip. He was running a brand new 1984 Camaro and this was in 1984.
My stock truck blew his doors off.
I ran just under 13 in the quarter for 3 passes. We were running best out of 3.
I remember when I punched that truck there was always a short stall or hesitation and then what felt like an explosion.
That 390 would come alive after about 1/2 to 1 second after you floored it.
It felt like the motor was trying to roll over in the engine compartment.
You were just sure it was going to fall on it's face or backfire and it would jump to life.
I have no idea what carb was on that or why that truck had so much more perceived power than the next old truck I got that was a 79 with a 390.
It almost felt like my newer truck was detuned compared to an almost identical newer engine.
What carb do you think they had on that 1974 F100 390 package?
I had a 1560 cc 4 cylinder engine that had two big side draft 2 barrel Webber carbs that had over 900cfm back in the 80s. It ran great often beating small blocks in light to light races. It never bogged but was a bit peaky and liked to rev. Often up to 8000 rpm through the first couple of shifts.
What was that, a Volvo b16?
What is maximum performance? My 84 El Camino Super Slow came with a 600 Edlebrock. Complete dog. I installed a 450 quick fuel, and it runs like a scaulded dog😂 It does cute lil one wheel burn outs and third gear pulls hard, all the way. Great MPG, great acceleration, starts on the first bump, every time, runs cool and never loads up during accessive idle. It is still only 200hp, If that. most of my torque is available off idle to 4 grand. for my daily driver, that is fantastic performance😂🇺🇸🇺🇸🇺🇸
For your purposes and engine, that 450 works fine, but I would have tried leaning the Edelbrock down a bit before making the switch. Some Edelbrocks are calibrated very rich from the factory
@@UncleTonysGarage I don't doubt you a bit. I had to weigh my abilities and time😂 If I found your channel a year ago, I may have. Edlebrocks are foreign to me. I know they are generally set it and forget it.
I did put a UT power tune, on it. 1/2 centrifugal lock out, the ol UTG delete a spring trick, and added weight to the advance weights. Runs so good, I like driving now😂 Serious, it runs like a current computor command EFI. All courtesy of this channel❤🚗🚓🚓🚓🇺🇸😂
Love these vids, Uncle T. Stuff I never knew!
Very interesting .. Thanks for the information ... I'm gonna try it on my dodge 383 with the stock carburetor ...
I watched till the end lol truly appreciate the breskdown
This video alone is worth a subscribe. Lots of knowledge