How to Choose the Right Size Carburetor

[@robpeters5204]

Thank you for such an informative video! I’ve been telling guys since the early 80’s that you have to spec your components for what you want out of it. They always said bigger is always bigger and you have to chrome it, etc. I’ve grown up trucking in my blood with the family business. Every truck is different and has to be spec’s out for different applications. If you spec it wrong, it will not be able to do what it was intended for and you can’t make money from it. It will end up costing you more money just to operate if at all. You explained it very well. You have to first figure out what you want out of it and go from there. That is why so many guys go and buy that dream car and end up crashing it moments after picking it up. You have to know what the vehicle is capable of doing and what you are capable of doing also. Once you get all the parts of the equation down, you will have a near perfect machine! I say near perfect because we are never satisfied once you start down this road. lol! Thanks!

[@MuscleCarSolutions]

Thank you! You bring up lots of good points. I like to take as much guess work out of things. If you can at least have a process, you can anticipate the results.

[@mattbauckman9907]

Even before seeing this, I believe most guys have too much carburetor on their engine. 750 cfm seems to be the default carb everyone uses, but I chose a 600 cfm for my bone stock 396 325 hp big block. The street manners and throttle response are impressive, better than any of my injected engines in fact. I've had many guys tell me I need a 750, that a 600 is too small etc. but nope.

[@MuscleCarSolutions]

Really all depends on what you use it for and what it’s set up for. I worked on a set up this morning that was WAY over carburated. I offered to tune one of mine on his set up to prove it. It really common and like you mentioned, doing it right will get you a better running engine. Thanks for watching!

[@bobkonradi1027]

Interesting, anybody's 350 cid V8 at 5000 rpms only needs around 375 cfm, maybe 400 cfm at 5000 rpms, and most street cars never go to a higher rpm than this. Yet most guys never go lower than 650 on a carb, and many go to 750. We need to be realistic when we enter data as to what the revs are going to top out at.

[@bigbelconut]

​@@bobkonradi1027 and the factory carb was a 750.

[@bigbelconut]

The factory carb was a 750 Q-jet, the 350 hp 396 had a 750 holley carb.

[@mattbauckman9907]

True. It’s easier to pick one carburetor and put it on everything than to switch it up. Doesn’t mean the engine is using all 750 cfm. They put 750’s on 305’s and the secondaries wouldn’t even open all the way even at 5500 rpm.

[@MarianoLu]

If anybody is wondering the 3456 comes from converting cubic inches to cubic feet and from considering that the car is 4 stroke meaning you will only pull air every other rotation.

[@Necronomous]

Then it means you need to half these numbers when using a 2-stroke carb. Or am I wrong?

[@chestrockwell8328]

Few weeks ago Brian helped me work through picking the proper fuel delivery for a project I'm working on; very nice and knowledgeable guy. Thanks again Brian.

[@MuscleCarSolutions]

Best of luck with your project!

[@cliffpeerson1426]

When towing or using engine in a heavy vehicle go smaller CFM. Air Velocity is what we are after in carburetor sizing. We want high air velocity so the carburetor works properly plus to fill the cylinders well especially at low rpms. If air velocity falls off due to carburetor being to big low end suffers. That's why smaller for towing and heavy vehicles. You can go bigger with lighter vehicles and higher rpms engines. When driving on the street we don't see much past 3500 rpms so the high air velocity of a smaller carburetor provides a much better driving experience. Good stuff!

[@ernestadamsjr.2662]

Just ran across this video. It was VERY informative. Here is my dilemma: I have a stock 350 sbc in a 72 Impala coupe (weighs about 3900 lbs.) with a 200R4 transmission and 3.73 rear end. An Edelbrock 1406 (600 cfm) sits atop a dual plane intake manifold that is fed by in-tank pump (max psi: 49-50) regulated to 5.5 psi by an AER fuel regulator. Max RPM for the engine is 5500; however, I have yet to hit 4000 even on the hills in my locale (3800 was the highest so far). I do not race but use the 3.73 gears for acceleration and the 200's OD to cruise. The 1406, IMO, burns too much gas. Edelbrock recommends the 1406; however, an older mechanic I know suggested moving to the 1404 (500 cfm). The math in your video also supports that mechanic. I'm looking for a final confirmation prior to spending the money for a new carb.

[@MuscleCarSolutions]

If you’re only spinning it to 4000 rpm, then that’s your number. Make the switch to a 500 and then TUNE it for your application. It’s not correct right out of the box. Never is. Once it’s tuned, then you can determine if it was the right move. Sounds like it will be.

[@ernestadamsjr.2662]

@@MuscleCarSolutions thanks for the IMMEDIATE response 👍

[@MuscleCarSolutions]

@@ernestadamsjr.2662 sure thing. Best of luck with it! My family had a 72 Impala sedan when I was a kid. Love those cars!

[@williamhenderson2661]

I just let your video audio Play in the shop when I’m working and not in the mood for music. It’s great background noise that also refreshes knowledge

[@MuscleCarSolutions]

Nice! That’s pretty cool actually. 😆 I’ve always wanted to be background noise! Thanks for the laugh. I really do appreciate that and glad you found a way to listen. It’s a great idea! I might start doing the same.

[@rjgenua4435]

Man iv follow you. I got a 350. 1972 Monte. It's a cruiser. But she likes to go fast. I put the fuel just like you I'm sitting at 5000 in Colorado. Adjustments made according to the chart. Still runs rich rich

[@Ratridez]

I'm running a junkyard low compression dodge 360 , edelbrock 340 manifold , A body manifolds true dual in a 3300 lb car and 373 diff with a edelbrock 600 cfm , mostly in town driving . Runs great , amazing fuel mileage and spark plugs are a light brown .

[@tareqshalsh9315]

I have chevy small block what size is best for saving fuel?

[@AreaThirteenThirteen]

I had a '77 Camaro back in the mid to late 80's that had a .40 over 350 with flat top pistons, roller rockers, stock exhaust manifolds a TH-350 trans, stock converter with 3:08 rear gears and 305 two barrel heads with small ports and an RV type camshaft ( I don't remember the brand name or specs on it though) that had an almost stock idle but you could tell it wasn't completely stock, the intake was a dual plane Edelbrock performer and I put on a 600 Holley with vacuum secondaries. I dont remember if the Edelbrock carburetors were around yet but the Holley was just over $100 brand new back then. I never had to fool with the jets or anything other than the idle speed and mixture, it ran pretty well out of the box. I ended up daily driving that car for quite some time. I had to watch the fuel quality and timing since the 305 heads bumped up the compression a bit but it had excellent throttle response and averaged around 17 MPG on the highway. I'm sure the cam, heads and exhaust held back any real top end performance but the low end torque was good enough for what I used the car for since it rarely saw anything over 4-5K RPM. I still regret selling it along with the other old cars I used to have which were cheap and plentiful back then.

[@michionwheels]

Q-jets use the airdoor to tune the cfm.Everyone of them has at least the 750cfm potential i.e. of some rare buicktypes. The factory used the angle of the airdoor for setting the carbs to tamer or smaller engines

[@jerrym6404]

Correct but my understanding and experience with them since I was a young man..2 types 750 and a 800 CFM..Look down the secondary if thier is a nub sticking out.. It's a 800 CFM...looks like the tip of your pinky finger..Other wise smooth it's a 750

[@stuckinmygarage6220]

I just had an "Ah-ha!" moment at @16:10 . It took me a couple runs through your other good videos. U never know what you missed when you don't understand stuff. Thank you, again!

[@MuscleCarSolutions]

Nice! Well I hope you got the answer you were looking for! If not, just ask and we’ll figure it out. ;)

[@stuckinmygarage6220]

@@MuscleCarSolutions Thanks! Yeah. I'm trying to piece how it all works. Fun to learn. 👍 I'll have more ?s down the road...har har...

[@MuscleCarSolutions]

@@stuckinmygarage6220 all good! I’ll be here!

[@williamhenderson2661]

Lol, here I am again listening to your videos. Just put all the side markers in my Mach 1. A tie rod end. And adjusted my reverse band all while listening to these

[@MuscleCarSolutions]

Appreciate that! Hopefully there was something in there you found useful. 69 or 70 Mach 1 is a bucket list car for me. One of these days!

[@Reece_466]

thanks for clearing alot of this up, I have been looking for a Holley DP for my 466 BBF in my 78 f100 street/strip truck (mostly street realistically), have been concerned about going to little or wasting time over carbureting

[@MuscleCarSolutions]

It’s a common mistake. It’s easy to say go way bigger and think it’s better than finding what the need of the engine is.

[@yurimodin7333]

Great video, alot of guys over cam & over carb their street engines......I am building a 350 Vortec and I picked up a used 600cfm Edelbrock Performer(gonna do a rebuild on it just to be safe). This entire engine is being designed around that 0-5,000 rpm street tourque band. Scored a dualplane non airgap intake. If/when I change the cam I am going for a tight LSA (probobly 108) with a 0-5,000 appropriate duration etc. I am all about that throttle response since I am gonna spend waaaaay more time at 3,000 rpm vs 6,000rpm.....heck I am gonna roll manifolds since headers are a nightmare. Hp/cu-in in a light weight 2wd GMC Jimmy is gonna be FUN.

[@bobkonradi1027]

Interesting: The Holley website has a formula and also a little electronic tool where the data is entered and then you get an answer as to what size carb to use. Edelbrock has the same thing. HOWEVER Holley then says to take the cfm recommendation and add 15% to it, for whatever reason. Edelbrock doesn't say this. They just stick to the initial number that their little electronic tool spits out. Both websites do agree, though, on the fact that you have to be realistic in what rpms you're actually going to run the engine at. Don't tell the calculator that you're going to run to 6000 rpm (or whatever) and then actually you never go over 5000.

[@thewoodsman5261]

Great video by the way very informative for people such as myself. My truck has a 700r4 tranny and the axel gear ratio is unknown at the moment.

[@CKirk2727]

First - Thanks so much for all your Wonderful Video's. I've never been very well versed in Cars/Working on them. But have just acquired a new care "to me" and have been trying to learn about Carbs and how they work and how to work on them and your video make thing very clear and understandable even for a 71 yr old Rookie ;-) So, I have a 1990 Chevy 383 Stroker Motor, in a lightweight car (2700lbs) not sure of any of the internals with the exception Of it came with documents for an Isky Mega 280 Cam, and it has an Edelbrock 1405 that has had an Electric Choke added at some point. I did check the Metering Rods and they are the .070 x.047. I've been learning about the timing and have 18 deg Adv and 34 in at about 2500rpm. Hope this is enough information to be able to make some suggestions. Thanks again, Take Care, CK

[@MuscleCarSolutions]

Glad you’re enjoying the videos! So the root question here is the 600 the right carb for the 383 in a light car. First things first. We have to ask the question, “what are you doing with the car”? Just a fun cruiser or something more aggressive? I don’t know a thing about the specs on that cam but I’ll assume they’re around 230 and a fairly tight LSA. 107? That cam is likely going to be done by 6500, so now we know what the max rpm is. The rest is simple from the video. On a lighter car, a little more CFM isn’t a bad thing. If you’re going to work in the power band of that cam (if my assumptions were correct) then a 750 would be a great carb for that set up. Just have to make sure the rest of the engine combination match and you’ll have a screamer of an engine!

[@CKirk2727]

Hi, Thanks so much for the reply and information. I'm just going to be cruising around in it on Nice Sunny Days. I think all in at 6500 is probably all my Heart can take ;-) Appreciate everything, Take Care, CK

[@MuscleCarSolutions]

@@CKirk2727 I just found that cam. It’s not going to be a lot of fun for a cruiser. It will sound good, but it’s going to be down on power below 2500. Not very fun. I’m assuming that’s what you’re after though. In which case, the 600 might be ok.

[@CKirk2727]

Hi, LOL I had that feeling even with the short amount of time I've had it and driven it. BUT It is what it is, at least now I know and so that will make things a lot clearer on it's performance, and drivability, and makes me feel a little better about my driving and tuning attempts. Thanks so much again for all your Help and the Great Video's I've learned a lot !!!

[@erbthatsright1103]

Thanks for mentioning the dump truck engine. I’m I’m the beginning stage of planning a rebuild of a Ford 460 for a stake body that it’s sole purpose is to haul firewood. Not much information about building high torque low RPM work engines.

[@MuscleCarSolutions]

Yup. Every year I get quite a few low rpm, high torque applications to help select components for. Dump trucks, yard dogs, logging trucks. Lots of gas powered stuff out there. Surprising how small a carb will work for a 460 when you’re only turning it less than 4000 rpm. Good stuff! Thanks for stopping by!

[@roha8993]

When I was a kid, the math was, max rpm x ci displacement ÷ by 3456 = cfm flow of engine. Add 10-15 % for low gear ratios low vehicle weight ECT.

[@bryanrodriguez6759]

Hi there so I have a 78 bronco with a 460 out of a 70s motorhome. Can’t get it to run fast and efficient lol what carb do you recommend. Currently has a 750 with Edelbrock dual plane manifold

[@MuscleCarSolutions]

Not sure I understand what you mean by fast and efficient. What is it doing that you don’t like and how have you attempted to tune it? What size did you come up with after watching the video?

[@johnbutler1323]

425 cadillac bored .600 due to cylinder wall damage, so 439 Cid. Stock cam. Dropped into a 64 Buick LeSaber with 3.42 rear gears. Max rpm before valve float is 4500 rpm. Torque peak is 2000, horsepower peak is 4200. I honestly thought the car had had higher rear gearing, but it was originally a manual car with a 300 Cid v8. They all got deeper rear gears. 2000 rpm is 50 mph. Top speed is 107 before valve float shuts it down. Car is primarily a weekend cruiser. I have a 750 cfm Edelbrock on it. Original carb was a 800 cfm Quadrajet.

[@MuscleCarSolutions]

The Qjet can be a little deceiving when you just look at the CFM number. Yes it capable of 800 CFM but I’d you look at the primaries, they are in fact substantially smaller than the secondaries. It’s how GM wanted to control the fuel and give the air and fuel needed when the demand was needed. The difference in the two carbs really can’t be compared on CFM alone. But you certainly have a lot of cubic inches to feed if you decide to go bigger on that cam! Awesome to hear you’re running a big Caddy. Always fun to see those big old school engines still on the road!

[@johnbutler1323]

@@MuscleCarSolutions Thanks for the reply. I got the Caddy and TH400 behind it pretty cheap and went with it. It's been fun, but frustrating at times. Partly because I chose a car that isn't common, and an engine to swap that isn't common, either. I'm considering upgrading to a mild cam and stronger valve springs to go to 5000 rpm.

[@MuscleCarSolutions]

@@johnbutler1323 that’s the downside of the cool factor. Fewer things available for their engines that don’t have a lot of volume to support lots of aftermarket parts. Which just makes what you’re doing even cooler!

[@johnbutler1323]

@@MuscleCarSolutions Thanks. One of the crazy things about the 425 Caddy is they debored the big 472 from 4.3" to 4.082" and kept the same 4.06" stroke. When they did, they knocked off every ounce of excess metal in the block and heads and actually opened up the water jackets quite a bit. The 425 Caddy big block weighs 100 lbs less than the 472 it's based on, putting at 525 lbs, which is 50 lbs lighter than a fully dressed Chevy small block with iron heads and intake and comes out about even when the Chevy small block has aluminum heads and intake. It's a very light engine for its displacement, especially considering it's all iron. The block is so light, I could pick it up and carry it around when it was stripped. It does take up a lot of real estate, though, and is every bit as wide as a Ford mod motor.

[@reginofung6028]

I used to race a 454 Chevy Big block with rev limited to 7000 . According to equation 1 , The engine should have a 930 cfm carb. I used both a 850 and a 1050 carbs. The 1050 worked better. Iddle was lower ( 900 rpm compared to 1200 rpm with The 850 carb. ). Power was Also better with The 1050. For racing, The equation si a little bit conservative.

[@rolandsgarage8640]

So glad I stumbled across this. I'm building a 351w for a 92 f150 4x4 AOD transmission. I'm running a .513 lift 270/276 duration 110 lobe separation roller cam. Stock Gt40 heads with a spring kit an edelbrock performer intake. Motor will be natural aspiration. Cam is rated 1500- 5500 rpm and intake is idle - 5500. It will be a daily driver and toy hauler. I have an edelbrock 1405 600 cfm sitting my shop now, but im wondering if I should step up to one of the new avs 650 cfm. Great content btw.

[@MuscleCarSolutions]

I’m glad you found it too! I don’t think you can go wrong with the AVSII. Sounds like for what you’re doing the 650 will be exactly what that combination is calling for. The windsor engines are exceptionally versatile and should deliver everything you’re asking from it!

[@troyboy9308]

I built a 351w 0.030 over 9.6.1 with a typhoon hi rise Intake. I also am running the same roller cam and I put it in my 87 f150 4x4 with a C6 and 3.55 gears. I have tried a 750, 725, 600 and currently using a 570 (all carbs are Holley) so far I think the 570 works the best.

[@GrandeTime]

Love your content, I have an 86 cutlass supreme with 307, nothing else done. It would not run with the q-jet, so a friend gave me a 1406. Not looking to race, just have a little performance and decent gas mileage. I think this 1406 is way too big and getting about 10 mpg, where I used to get 20 mpg with the q-jet. Again love your channel and thank you.

[@MuscleCarSolutions]

Yup. 600 CFM on a 307 is over carbureted. Get a 500 and tune it. Thank you! Glad you’re enjoying it.

[@GrandeTime]

@@MuscleCarSolutions great thank you, which 500 do you think; 1901

[@MuscleCarSolutions]

@@GrandeTime yes go with the AVS2. Either manual or electric choke - your choice.

[@KingJT80]

i had a carter AFB 500CFM carb 20 yrs ago on my 80 impala sports coupe and that had what they called an "Rv cam" 204/214 duration @ .050 and that was more than enough had the stock freeway gears stock heads and i found a cast iron 4bbl intake

[@gfalexan]

70 chevelle 10:1 383 230-240 , advertised 280-290 duration, 489 int lift, 519 exhaust, rpm air gap intake, header and full 3' exhaust, th350 2500 stall and 3:42 gears.

[@airkore]

307 Small Block in a 3/4 ton manual 4 speed GMC pickup. Street drive only with a mild RV cam. Thanks for the great information.

[@MuscleCarSolutions]

Yup. You’ll have a much smaller CFM carb on that application for sure! Thanks for watching! Glad you found it useful!

[@aussielad88]

I had a slant 225 ran a 600 double pumper on it ran like a dream with the 4 speed manual

[@MuscleCarSolutions]

The ole pig rich, but it still runs so it must be right theory!

[@mogie620]

Awesome man Ty. I’m using 93 octane 1978 stock vette 350 and according to this a 650 is more than enough for street driving. I got a 670 avenger holley

[@MuscleCarSolutions]

Sounds like a good choice!

[@jeffjohnon4223]

600 Edelbrock on that, I bet that Avenger gets horrible mileage.

[@jb-wj3wn]

I have a 1978 ford weekend fun truck 2wd 460 .040 over Flat top pistons to bump compression of the Stock 3dve heads Performer rpm Intake Holley 750cfm vacuum secondary 1970 straight up timing set Headers 2.5” dual exhaust Manual transmission 4800-5000 rpm max Runs good But is old and was thinking upgrade Since I have no other carbs to compare it to , I was considering an 800cfm edelbrock avs2

[@MuscleCarSolutions]

Maybe. But that’s a very mismatched intake. It works from 1600-6500. You’d be better off with the performer that works off idle to 5500.

[@LarsR.Christensen]

First of all thank you so much for superb information regarding carburation. You have put my understanding of carburation to another level. Thanks again. I have aquestion for you thats puzzle me alot. I Have a '70 Cadillac Deville, stock engine (375 hp), stock TH400 and stock 2.94:1 rearend. Never passes, and never will, 5000 rpm. When the QJet came to age i put on a Holley 4160 600 cfm (0-80457s). I have a O2 sensor in my exhaust so i can check AFR. What puzzle me is that when passed idle i have almost perfect 14,7:1 AFR. But.... at idle, whatever i adjust or fiddle around with, it never go past 12.0:1. So my idle is a little rough and smell rich. Is there anything i am missing out when adjusting idle or do you have any idea why my AFR are so low in idle?

[@robertclymer6948]

Great info as usual! Appreciate all the knowledge you share with the car community, it really really helps!! Thank you and cheers from Motown. Oh, new subscriber and hit the bell.

[@MuscleCarSolutions]

Nice! Thanks for that. Just years and years of being around it and making many mistakes. Glad you’re here! Don’t hesitate to ask any questions. I try to answer them all. Motown thawing out and summer is almost there!

[@robertclymer6948]

@@MuscleCarSolutions We have hit over 80 this week and set records. Scrambling to get my Mustang full spool out and go with a LSD so I can turn the darn thing. Also struggling with Deadhead or Bypass regulator. Probably Deadhead with gauge port Holley 12-840, if any problems will do bypass over winter. Mild built 460, RPM performer, Holley 4160 750,MSD 6al, C-6 manual valve body, full headers, 3" into magna flows, nodular 9" 4:11 gears, 4 link, was ex 8 sec race car, streetable now. Thanks See ya soon.

[@MuscleCarSolutions]

@@robertclymer6948 sounds like a heck of a fun ride!

[@bcframers5423]

I run a quick fuel brawler 650 on a built amc401 took a little tuning but works great. AFR gauge is key to carb tuning

[@MuscleCarSolutions]

Always will get the best results with an AFR.

[@paulhare662]

Howdy. Just found your channel, subscribed and will be viewing more episodes as time permits. I'm taking a bit of a backwards journey from the bigger, faster, louder way of thinking. Car is a 65 Chevy Two station wagon with a 350 topped with Edelbrock Performer RPM heads, intake and 1411 carb. I have removed the RPM cam and installed a Summit 214/224 mild "RV" cam, chucked the 350 turbo for a 700R4 and am currently rebuilding a 1406 carb for it. I drive it a lot and with fuel costs what they are, MPG is important. It cruises the interstate at around 2400 RPM, has 18 in. idle vaccum but still is lousy on gas. The 1406 has factory tune jets/ rods/ springs. Any suggestions? Anyone else shooting for more MPG not worried so much with ET anymore? Doing the math real quick, I come up with a 405 CFM being sufficient.

[@MuscleCarSolutions]

If fuel economy is truly what you’re after, a 500 would have been the better choice. But aside from that, the next video you should consider watching is kzbin.info/www/bejne/rITJcpWJfZ6Bh80

[@MuscleCarSolutions]

It’s the way the OEs have gone after the growing restrictions on economy. Keeping the operating rpm as low as possible will increase fuel economy. Less rpm means less fuel used. So a modern 6 speed would be an even better choice. You’ll see the largest gains in the trans. Welcome to the channel! Eager to hear how your quest goes for more MPG!

[@ahmadbeepoetic5606]

I'm running a hot setup on the street. It''s 468 big block Chevy with a 7,000 RPM range. According to the formula it equates to approximately 947.9 (950 cfm). As of right now I am running a 950 carburetor. Pretty much spot on. However, I'm running a FST 4500 series 950. My question, is there a big difference between 4150 style base plate, and a 4500 style base plate? The car loves the 4500 at high rpm.

[@ericthompson3551]

I’ve seen this discussed on engine masters and the saying an engine has too much carb didn’t play out on the Westech dyno.

[@MuscleCarSolutions]

So put too big a carb on your car and see how it is driving around town. Dyno and real world operation are two entirely different things.

[@KingJT80]

it wasnt that it was too much carb. it was more of the TYPE of carb. but i know which episode youre talking about but they did another episode and a double pumper is obviously gonna flow more fuel. thats why they made 24 more HP vs a vac secondary of the same size. both flow 750 CFM. fuel curves are completely different. mechanical secondaries flow more on the secondary side . exactly why the double pumper is what it is, an extra shot of fuel,.

[@pnwoods]

Thanks, much, Mr. ... Picked up an old stock '70 318 Dodge W200 Power Wagon, truck gears, seldom over 3000 rpm, Carter BBD 2 barrel. .. Shop manager, & local mechanic suggested a low rise/ 4 barrel Edelbrock. Folks at Edelbrock set me up with matching manifold & #1405 600 cfm carb. ... questioned Edelbrock's service dept. about size of carburetor, & they qualified it. ... ... Just about to install. .. This video suggests I would make an incorrect/troublesome decision. .... Any knowledgeable input is welcomed.

[@MuscleCarSolutions]

They’re always going to go a size larger. It’s way better to be on the rich side than the lean side but in this case, if all you ever see is 3000 and below, the 500 would have been a better choice.

[@Necronomous]

So, what I have learned for example is that a Pontiac Bonneville with a 389 means that a 700 carb ain't too much because my numbers ended up in 714 point something.

[@jessicaembers924]

You can use a little larger cfm on a full dual plane manifold, because each side is only Drawing off one side of the carburator! :-)

[@MuscleCarSolutions]

Incorrect. Using a larger size will need the air speed through the venturi and booster to get the fuel flowing as the carb was designed. If you run too big a carburetor, the speed isn’t there to meter the fuel correctly. Running the correct size for the application is always best. Doesn’t matter the design of the intake.

[@thewoodsman5261]

Hello from Canada! I recently picked up a 1977 GMC Sierra K15 4x4. It's 98% complete. The previous owner dropped in a late model gen1 350 TBI and running gear from a 1987 Chevy Suburban. It's not running it was just placed in, nothing hooked up. I would like to swap out the TBI set up and put an aftermarket dual plane intake and carburetor on it, possibly headers I can't find any cam specs on this engine but do know it makes 200hp and 300 ft/lbs, At what rpm I don't know. Realistically this engine wont be seeing to much time at high rpm, probably 5500 max. I keep doing my calculations with a 350 ci and 85% VE and the number keeps coming up at or around 470 cfmchevy. This seems way small for a small block Chevy. It's a truck build and I'm looking at getting the Holley 90470 off-road carburetor. The website says recommended for 4cyl, v6 and inline 6 engines. Is this carb a poor choice or just what I'm looking for. The next size up in this series is a 670 cfm. Im in Canada and these carbs are going for just over $1000, I gotta get this right the first time. Your opinion and knowledge means a lot to me right now, thanks

[@MuscleCarSolutions]

The thing is if you’re not sure on the cam profile or you feel like a 500 CFM carb would be too small, then put on a bigger one. I can tell you at that Hp level and likely won’t spin that thing past 5000 rpm, I’d have no problem putting a 500 on. But like I said above, if a larger size will make you feel better, then go for it. You’ll know if it was the right choice or not if the tuning becomes difficult.

[@pyphus]

I'm so lucky that you used the 351W as an example, since that's what I'm building! Is "Operating RPM" the same as "fast idle RPM"? Ford shop manual states fast idle RPM @ 1400. Seems very low, compared to 6,500.

[@MuscleCarSolutions]

Operating RPM generally refers to the zone in which the best power is made. If the set up was chosen to work together, the range is easy to determine. Most go by what the cam is rated at. It’s become a universal term of where the vehicle will be driving. Race car, high rpm. Street car, low to mid range and majority of the time.

[@robertclark7848]

I know what you’re talking about but my original 327 sbc Chevy run great on a 600 cfm edelbrock fine tune to my performance cam and heads , some guys think slapping a huge carb on equals more power while it can but it depends on what your doing I’m a street cruiser I like the power but don’t race my 67 Camaro and the 600 works great

[@MuscleCarSolutions]

If that size fits the rpm range and use of the car, then you’ve found the right size! 👍

[@rono3045]

The right way to do this is either at the track or on a dyno each change you make to your carburetor just see if you're faster in the quarter mile or slower same with having your engine on a dyno that's really the only way you're going to know if the changes you're making are better or worse.

[@MuscleCarSolutions]

Much simpler to just use an AFR for monitoring and tuning. The formula is a guideline. There are far too many otter variables as I mentioned that have to be taken into account. Sometimes it just boils down to years and years of experience to make the right call the first time.

[@b-17wingman37]

Thanks so much for the info . I have a 460 that I want to put an Edlebrock carb on .

[@StLouisSled]

Putting together a 289 Ford engine in a tiny 2500 lb Sunbeam Tiger. Small 270 cam, dual plane intake, stock exhaust manifolds, 4 speed manual. Will be driven conservatively with the occasional spirited sprint down the on ramp, maybe 5500rpm max. Math works out to 459 cfm. I'm thinking about a 500 cfm 4 barrel...what do you think? Do you know if Holley makes a 500 cfm carb? Or would Edelbrock be a better choice in this case

[@MuscleCarSolutions]

In this case with a lighter car, I’d use a slightly larger carburetor. 600-650 would be just fine. Everything you have mentioned would match up well with that. Part of the issue with these formulas, they aren’t an exact science. 👊

[@StLouisSled]

@@MuscleCarSolutions Thanks! Do you have a personal preference between Holley and Edelbrock?

[@MuscleCarSolutions]

@@StLouisSled all depends on what you’re going to do with the car. Drag race only? Holley. Street driving? Edelbrock. For what you explained, I’d lean towards the Edelbrock. Easy to tune and will be very friendly for what you’re doing with it.

[@kennethcohagen3539]

500 to 550 sounds fine. My friend used a 600 vacuum secondary carb on his 65 Mustang with a 289. Keep in mind two thing. A manual transmission can help a car with too much CFM. When I was in HS, we built a 10.90 comp car at the winter nationals at the old track just outside of Phoenix, Beeline Dragway. We ran a 283 bored out to 292 cubic inch engine. It had a solid roller cam and a 1050 dominator. Again, running a manual trans would have helped, but this high winding screamer was backed by a 2 speed powerglide automatic. It took a good tuner to get that combination running well. We ran under the index in the final, losing a 10.89 pass to the other guys 10.94. Kind a hurts when you lose because you went too fast!

[@MarkSpalding-qc7ym]

@kennethcohagen3539 I remember beeline in the 70s. Left PHX 20 years ago. Would run out there as an adult just to remember my youth

[@f150bft]

I was using a 1.08 Autolite 4100 on my 302 in my 78 Mustang ll, I thought it ran awesome.....until i put a Summit 600 cfm on it and it woke it up. I now have aluminum heads, BluePrint HP 9008's and a much hotter cam so I'm thinking a 750 might be more in line, it will see 7k rpms at times. I looked up a 302 boss (real) engine and it show it came with a 780 Holley. Your thoughts? I am a subscriber and I have learned a lot watching your videos.

[@MuscleCarSolutions]

If it’s a race purpose built engine and that’s where it’s going to operate. The 750 might be a bit much, but it will ensure your top end will remain rich. Given the small cubic inches and on a race engine, I’d run a 650 HP. Give some tune ability to the mid and high range circuits.

[@Fire.4Effect]

The Holley Carby maths is 99% spot on every time, be it N/A or Blown carb applications. There's waaaayyyy too many over carbed street cars getting around with that " mystery" flat spot at WOT

[@dedreman2227]

Huh

[@dylansretreat]

Hey your video are awesome, I’m learning every time. I just got a 1968 Chevelle with a 307 a 1406 and performer serie manifold intake is it too much? Runs nice at high rpm if I got stuck in traffic eddy gets flooded….I think

[@MuscleCarSolutions]

@@dylansretreat could be too much. Really depends on the things I mentioned in this video. Tell me about the 307. Is it stock?

[@349a4]

Thanks for the awesome video! I have a 289, uprated cam but nothing too aggressive in a 1931 Model A hot rod. Pretty light car, I would guess around 2200lbs and its a automatic. Currently has a 600CFM Edelbrock Performer and I’m thinking about moving to a AVS2. Its street driven with 91 pump gas. Thinking a 500CFM?

[@MuscleCarSolutions]

@@349a4 probably. But also need to know the cam specs so you’ll know what the engine is capable of RPM wise.

[@349a4]

@@MuscleCarSolutionsI appreciate the reply! The car is new to me and the internals are unfortunately unknown. It has a very slightly lumpy idle and it still pulls well off idle which is all I know about the cam. My assumption is pretty mild but bigger than stock. I calculated with the assumption of 6500rpm.

[@MuscleCarSolutions]

@@349a4 so in this case, you can just go by how you’ll drive it. If you’re going to put it on the cams redline often, then yes use that rpm number to calculate your decision on a CFM size. If you’re not planning on driving it that aggressive, then you can use that number. If you go the second route and you have a situation where the math gives you a number in between two sizes, then go with the bigger option.

[@Trump985]

The problem is 4 barrel carb CFM ratings are measured at 1.5 inches of mercury. So in order for a 850 CFM carb to flow 850CFM it has to be strangling the engine and you would have to have 1.5 in hg at WOT! It’s quite obvious that this carb will flow less than 850 CFM at a lower pressure drop. Now the question is how little pressure drop can you get away with? In my experience you can get a carb to work below .5 InHg with annular boosters and minor modifications. When it comes to 2 barrel carbs they are rated at 3 in hg! So in order to get flow rating of a 2 barrel your absolutely strangling the engine!

[@Trump985]

This is why a fuel injected engine will always make more power then a carburetor. A carburetor REQUIRES a pressure drop to function. If a carburetor has zero pressure drop there will be zero fuel flow. Fuel injection DOES NOT require pressure drop as the fuel pressure provides the flow so a fuel injection system should be sized to have zero pressure drop.

[@jrsgarage3244]

Dual plane uses 1/2 carb, single plane runs whole carb Major difference 🚩🚩👍

[@brandonnolen8729]

Love the video. Would love some input on my situation. I have an 87 suburban with a mild 454 BBC. Mild cam, long tube headers. Running a 4 speed manual and it’s also on 40 inch tires and 4.10 gears. (needs 4.56) Just a cruiser/ off-roader that I never take above 4500 rpm. But I do live in the mountains with lots of decent grades where you really need to roll into the throttle to get it to move. I ordered a Holley 570 street avenger because of the low rpms I consistently run but I’m second guessing myself because of the load it sees with the hills and grades. Any ideas would be appreciated!

[@jeffjohnon4223]

Get a Performer intake, not an RPM or an air gap. Just the regular Performer, they have faster air velocity that makes more torque.

[@joemesadiver]

Great video!! my application is a little different 350ci only turning 3000 MAX rpm on a airboat by your calculations a 500 cfm holly is more than enough. my question is i hear they make a 480 cfm holly 4 barrel would that be a better fit than the 500 2 barrel? Thank you in advance .

[@FanciscoNavedo]

Love the video I have a 462 Chevrolet with Pro race right heads elder aluminum 850 cam max rpm 6500 my spark plugs go bad very quickly. Is this carbureted working properly Is it big thank you

[@xpirxtion]

I got an 350 small block hard to find a carburetor here I need a lil help

[@ricardssamuls9152]

@@xpirxtion same here.

[@bigbelconut]

​@@ricardssamuls9152 what's the application?

[@nathanspeidel2969]

I have a 350 chevy in an 1981 Chevy k10. I installed a new crate engine in it to replace a worn out 305. I used an Edelbrock AVS2 650 with electric choke. I have the initial timing set a 10 degrees BTDC. The issue that I am having is that when it is warm out and I turn it off, it is hard to restart and acts like it is flooded on restart after 20-30 minutes. I have not made any changes to the carb at this point. I put hedman hedders and glass pack mufflers on it when I installed the engine 3 years ago. So there is no catalyst now. OE fuel pump, no regulator. I'm wondering if the fuel pressure is coming up with a hot engine and leaking past the needle and seat. I have a thermal shield on the fuel line from the fuel pump to the intake manifold, Edelbrock thermal mounting gasket and the adapter to mount a carb. to a quadrajet manifold also. Thanks for any advice that you can give.

[@MuscleCarSolutions]

It sounds like the thermal gasket isn’t enough. Should have plenty of room under hood to run a thicker spacer. I did a video on heat soak and ways to help cure it. What you’re experiencing is common with the crappy ethanol and fuel we have today.

[@averagebogarage]

I have a mild cam. Aluminum heads. Performer intake. Roller rockers and headers on a 351w. With that calculation it says I should be running a 500cfm 😳. Every hotrodder I’ve talked says I need to go up in cfm. I have a 600 on it now.

[@MuscleCarSolutions]

@@averagebogarage everyone should experience at least once how an engine runs and wears with too big a carburetor. Sounds like you’re being pushed into that lesson.

[@averagebogarage]

@@MuscleCarSolutions not now. Lol. One more question and thanks for ur reply. Would u go w 500 in my case or stick w the 600. It’s just a toy I drive around town and get on every now and then I’d say never anything above 4500ish rpm. Which works out to 507 using that equation. So 500 or 600. In ur opinion? Thanks again

[@MuscleCarSolutions]

@@averagebogarage if that’s your upper limit on RPM, both will work, but the 500 will be very easy to calibrate and have much better throttle response. Really all depends on the cam specs and how you’ll operate it. I just put a 500 on a 496 a few weeks ago into a tow rig. Flawless.

[@erniehampton5809]

Hi, very good explanation of how the carburetor works and how to do the math . I’ve got a 65 Olds Cutlass with a olds 403 .060 over, headers , olds 350 heads w 65 cc cambers 9.1 :1 , Edelbrock performer rpm intake, Carter 750 , isky 262 / 262 cam , stock rear ended , HEI TH2004r w lockup converter. Runs so so. I did the math and it looks like a could go with a 625 or a 650 CFM Edelbrock 408cid x 5000rpm 3456 = 590.2777 Any suggestions? Thank you for your time and efforts Job well done. Ernie

[@MuscleCarSolutions]

Kind of really depends on this one. I’d probably step up to the AVS2 and go with the 650. You’ll get some better throttle response with the annular discharge carb. Should have no trouble tuning it for that fun Olds motor. Big fan of any of the BOP engines and cars. 👍

[@erniehampton5809]

@@MuscleCarSolutions thank you very much for your prompt reply and time . Always a pleasure to talk with someone who has been working with this kind of thing . I’d send a picture of my car but this site won’t let me . Take care and be well Regards Ernie

[@MuscleCarSolutions]

@@erniehampton5809 always happy to help!

[@ericneilson1198]

Well without a tachometer, I'm sunk. I have a malaise era Elky (145 hp, 2bbl, 5.7). just need enough power to pass slow moving semi's on a 14% grade maintaining 65 mph.

[@jb-wj3wn]

Trying to figure out carb size 78 Ford F-250 pickup , 2 wheel drive .daily driver 78 460 bored.40 over , flat top pistons, rpm dual plane intake , 3” headers, mild cam , 70 429 timing set , zf5 5 speed manual transmission , stock heads I believe..currently has a Holley 750 but considering edelbrock avs2 650 or 800cfm

[@MuscleCarSolutions]

Well, ignore the intake that’s mismatched to your combo and tell me what number you came up with in the equation? It’s usually very close to what size you’ll actually need.

[@jb-wj3wn]

Thanks for the response.. I’m getting 575 cfm by plugging in 468 cubic inches and max rpm of 5000 on a few different carb size calculators so my 750 is way too big .. the intake was on the motor when I purchased it and not sure the cost to replace it is worth it …. Also I’ve heard that edelbrock carbs flow less cfm than Holley of the same size .. any truth to that

[@rong4189]

I’ve heard several times that Holley and Edelbrock use different vacuum ratings for their cfm ratings?

[@MuscleCarSolutions]

It’s an interesting question. I know they are all a little different in how they are rated from the manufacturer. What’s interesting is when they are flowed with one manufacturers process, and you put another brand on that used a different process, you’ll get a different CFM rating. Doesn’t mean it’s wrong, it just means a different set of standards was applied in the rating. I’ve thought of doing that video but I don’t have a flow bench at my disposal.

[@woodrowkirkpatrick207]

I have a 84 Silverado 3/4 ton truck with a 350 motor. Truck will be used for towing/hauling and weekend driving. It had an edlebrock carb when I got the truck but I want to upgrade it. Holley 600 or 650? What do you recommend?

[@MuscleCarSolutions]

If towing and hauling are your plans, the Edelbrock is a better choice. Holleys works exceptionally well in WOT and racing situations.

[@mikelyle6697]

I got a 1971 Chevelle 402 big block 4 speed Bored over 30 on the cylinders. Trying to find the right carb for street use

[@MuscleCarSolutions]

Nice! What did you come up with?

[@allansnow4516]

Kingswood ute, 308 CI W/ 204/214@0.050 lift camshaft, 9:1 CR, 3.00 diff gears, 4 speed manual, Edelbrock Performer Intake manifold. Mostly highway and daily driving use, barely ever go over 3000 rpm.

[@MuscleCarSolutions]

Would love to see more Utes here in the US. Love what the car culture is in Australia!

[@allansnow4516]

@@MuscleCarSolutions Quite bit over here. What kind of carb would you suggest for that? Currently running an Edelbrock AVS2 500cfm however going off all those calculations I should see 350-390

[@MuscleCarSolutions]

@@allansnow4516 depends on the things talked about in the video. What’s your cam specs? How are you planning on driving it? Other engine mods? Without knowing more details, you’re probably ok with the 500cfm especially if you’re going to keep the rpm down that low. Would be a very nice responsive system.

[@allansnow4516]

@@MuscleCarSolutions Cam rpm range 1700-4700, 9:1 Compression, Dual plane manifold, High flowing exhaust, car weighs 1300kg ,3.00 diff ratio. Majority country roads and highway driving (100km/h).

[@MuscleCarSolutions]

Sounds like a nice carburetor for what you’ll be using it for. Have fun! Cheers!

[@sb328]

Hi. I know this is an older video but I greatly appreciate it none the less. Hope I don't overload you with info here but.... I'm less confused after watching it but still wondering which way I should go, possibly because there are so many people running over-carbed motors and I can't seem to shake that. Anyhow, I have a 66 mustang fastback with a 72' 302 and C4 3 speed Auto. It was my Dad's years ago and I managed to buy it back... cool story actually. Anyhow, I have no idea what the cam is but It definitely sounds a little more aggressive than stock. I still get 18 hg at idle from manifold when tuning so its not a crazy cam. It also has dual exhaust with long tube headers, H pipe with flowmasters (40s I think) and currently has a Holley 650 Double pumper (List 4777-3) with mechanical secondaries. Stock mechanical fuel pump. Fuel I usually run is the shell v power nitro + 91 octane (10% ethanol I believe) with a bottle of lead substitute and Orielly's octane booster. I drive pretty conservatively and only cruise it. Will never see a race on the street or strip but I might stomp on it when getting on the highway. When I run the formula, 302 x 5000 / 3456, I get 436.92 CFM. Quck Fuel makes the HR-450, a 450cfm double pumper with vacuum secondaries and Summit makes the M2008 500cfm DP with Vac. secondaries. I guess I'm ultimately asking if that's the cfm area you think would be ideal (is 450cfm enough) and if you think either of these carburetors are a good choice. OR, what would you suggest? Again sorry for the napalm of information.

[@MuscleCarSolutions]

So the question would be, how does the car run with the 650?

[@sb328]

Very sluggish from the line but has plenty of top end power at 65mph highway speed. Idles rough for sure. Had the carb rebuilt and spent hours tuning it to get rid of the stumble it had on initial acceleration.

[@sb328]

​@@MuscleCarSolutionsand wow. Thx for the quick response.

[@MuscleCarSolutions]

@@sb328 so you tuned out that hesitation and it runs well now? If that’s the case, then what’s the trouble?

[@sb328]

@@MuscleCarSolutionsNo, I tuned out the hesitation but it still idles rough and is sluggish. I thought maybe it was low compression but I checked all the cylinders and they're all in a good and equal range and there's no leakage from the valves if I let the gauge sit there a while, so compression is good. So I'm just thinking its over-carbed. Thought by dropping to a smaller carb I might get a smoother idle and a little more pep on the street. Just not sure how much lower I should go. My options are 450, 500, 570. Plus I'd like to keep the driver side fuel inlet as that's where I've got factory hard line running to and would be a cleaner look in my engine bay.

[@davidparker6415]

Awesome and enlightening video! I recently purchased a '67 GTO with a 400ci and Edelbrock 600cfm, intake and a 2004R w/od trans. Runs rough and runs on. I'm now running 93 octane and I'm thinking a Holley DP 750cfm and new TV cable/throttle setup. Am I on the right track? TIA.

[@MuscleCarSolutions]

Don’t know. What was the size CFM you got from the information in the video? What are you using the vehicle for? Drag only? Cruiser? What have you done to address the running issues you’re having? I’d be a lot more concerned about those before I made any carburetor changes.

[@davidparker6415]

@@MuscleCarSolutions I’m looking at 400ci at 6000rpm w/93 octane came to a 750cfm. Definitely a cruiser. I’ve run the higher octane and even tried Seafoam but to no avail.

[@MuscleCarSolutions]

What’s your timing set at? Initial and all in?

[@jaydurych]

When that thing was new, it probably ran great from the factory using a stock 750 CFM Quadra jet. I know gas today is not as good as it was in 1967, but the engineers at GM knew a thing or two. I would try a QJ.

[@heinzmichels8535]

Thx for the vid! Do you think a stock 351 Windsor 2 barrel will benefit from the "big" Autolite 2100 from a 2 barrel 390? It's one venturi size above the stock carb. Stock cam street driven, FMX auto. It ist more about fiddeling around and finding the sweet spot set up for the car.

[@jeffcampbell2710]

How about a Ford, 351M-400, stock, with an Edelbrock performer intake, Holley, may even put on some headers. IT hauls garbage off on Saturday. Goes by the church to work. Go to the Hardware. And back home. An occasional 50 mile round trip to work and back. By this video, looks like it needs a 500 CFM.

[@MuscleCarSolutions]

500 CFM could be right. That’s a low rpm torque engine. As long as you don’t have anything that would take it past that 4000 rpm mark, I’d be 100% ok running a 500.

[@jeffcampbell2710]

@@MuscleCarSolutions Yea, I'm not building a race engine. It started as a timing chain. My friend brought it for a parts truck. But, in 79, they had them choked down for emissions. I just want it's full potential. Not rebuilding it. But it's got serious gunk from sitting probably 15 years. And I'm just taking the intake off before I even try to start it. Compression feels good, but gonna yank the heads and take a look, have the heads worked. So I thought an intake and Holley would get all it's got to offer. It will be a good Truck engine. It's a camper Special truck. Someone took care of it at one time. I assume they died, it sat, and got sold for junk. I just love making old things run again. I'm a body paint man mostly thou.

[@mini_maniac4205]

Just purchased 66 gmc believe it had stock motor and carb 305 v6 and strombreg 2 barrel wondering where I’d be able to buy a remanufactured carb possibly or how to figure out what aftermarket carb would fit on it just for daily driving

[@MuscleCarSolutions]

Last time I looked there wasn’t a heck of a lot available for those engines. They’re for sure different, but I’m not sure how easy it’s going to be if you want to upgrade anything. I’d have a builder go through the factory carb and leave it be. Unless you plan on swapping the engine to something a little more modern. Then all options are available.

[@josephkiszczak3889]

I've got a 72 ford 390 fe, rv can this thing rarely sees 300 rpms I've got a 570 cfm holley carburetor on it, I think it came with a 2 barrel I think, but I do like to go fast a little bit

[@boss351gt6]

Back in the day many engines came with larger carbs. Take the boss 302 for example, it had a 780 Vac sec. Howcome the factory put such large flowing carbs on? Ford had mandates on factory cars for them to operate smoothly so you'd think they would have put a smaller carburetor on.

[@MuscleCarSolutions]

Same with GM and the quadrajet. Mopar with the thermoquad. All very large CFM carbs used on smaller engines. Primaries are smaller so it would idle and cruise without using a ton of fuel. WOT and the secondaries open and in come in very large secondaries with a lot of CFM and.....leaded gas. Completely different fuel than today’s ethanol garbage.

[@mickangio16]

The car companies sometimes put bigger than necessary carbs on certain cars that were expected to compete in racing so that part would be factory installed and accepted where mandated.

[@BPattB]

I've been meaning to ask this question for a while so here we go. Do Holley and Edelbrock measure CFM the same. Another KZbinr I watch says "Holley is wet flow tested and Edelbrock is dry flow tested". He has a car with a tunnel ram with 2 600 Holleys he said that if he switched over to Edelbrocks he would have to run 2 750 Edelbrocks to match the 2 Holley 600's. When I bought my mustang it had a 650 Holley on it and since I switched to the Edelbrock I can't replicate the low, choppy idle I had with the Holley. The idle has a different sound completely. Anyway, as always thanks for sharing your knowledge!

[@MuscleCarSolutions]

The standard flow bench is used to measure CFM on prototype carbs. They’ll usually make a 3-D printed one these days so they can tear out the bore sizes to get the flow data and measure what the final CFM will be. Once it’s in a testing phase, that might get checked again (wet or dry) but it’s already been determined at that point. Your tunnel ram example is how they both meter fuel. CFM won’t have too much to do with it but it can be corrected with the linkage set up. The Edelbrock’s that I’ve set up will bring in the secondary carburetor earlier to get the fuel flowing to match the engine load. What your friend was describing could have been fixed with the linkage, not by going to a bigger CFM carb. To your last example on your car going from a 650 Holley to a xxx Edelbrock. Goes back to how it meters fuel. The Holley is more mindless - dumps more fuel. The Edelbrock is more calculated in how much fuel it delivers.

[@BPattB]

@@MuscleCarSolutions Right on, I appreciate you. If I continue to tweak the Edelbrock 1405 I should be able to get a lot closer to the same idle RPM and sound as the 650 Holley. That's good because I was about ready to give up lol. It's my information on the to Holly 600 comparing to two Edelbrock 750s came from a KZbin channel with quite a few subscribers. He actually gave you and your channel a lot of credit when you brought out the new Edelbrock race carburetor. He's great for entertainment and some technical things, but if I'm actually going to put my hands on a carburetor I'm checking your channel first for tutorial!

[@MuscleCarSolutions]

@@BPattB no. The Edelbrock doesn’t delivery fuel like the Holley. It’s going to sound different. It’s a much more efficient carburetor. Everyone has their own preferences and that’s ok. Some folks will say that everything else is junk other than their preference which is not ok. Different situations call for different solutions. That’s why there’s no one best camshaft for a 383 Chevy. Or big block mopar. FE Ford. Pick the right cam for what you’re asking the engine to do. Carburetors are exactly the same. Choose the one that gives you the best result for what you’re asking of it.

[@BPattB]

@@MuscleCarSolutions I totally understand what you're saying the right part for the right situation. So let me ask you this do you think a avs2 carburetor would give a different sound to the idle than a 1406? I'm soaking up so much of your time today I'm sorry. I have also heard and didn't believe it because I haven't heard it from you 😂 that the boosters on a 1405 are different than a 1406, is there any truth to this?

[@MuscleCarSolutions]

Possible. In all honesty it’s not anything I’ve observed. In a month or so I can possibly get to that and see. Good question!

[@nickrodriguez7293]

Thank you very much first time I've had this explanation. Installing a Holley 570 CFM for my 351m Ford F-150.

[@petskudahlman]

I have a '67 Dodge charger, 360cid (sheet metal kits/better camshaft) I put an edelbrock CFM: 600 on it with an electric choke, it worked really well, then the electric choke broke, I didn't know you could buy a repair kit. I bought a new edelbrock 600, manual throttle, I've never gotten it to work well, the nozzles have been changed and sometimes too much petrol or too little, when I'm sitting in a wheelchair, I can't install it myself anymore, Finland has good installers for sure, but they're too expensive for someone on a small pension , would it be a replacement, for example, a holley double pump??

[@MuscleCarSolutions]

Don’t blindly change parts. Figure out the resin for the issues and fix it. Just mindlessly swapping parts/carburetors isn’t going to solve your problem. Finding the problem is a whole lot less money than the expense of buying an expensive new carburetor every time. I’ve got videos on all the issues you mentioned.

[@petskudahlman]

@@MuscleCarSolutions is the edelbrock 600 the right size?

[@MuscleCarSolutions]

@@petskudahlman I don’t know. You didn’t provide enough info to make that statement. You watched the video? Based on what was in it, what CFM did you come up with?

[@waynetirey2730]

Yes I could use some help with my build, I’m building a 525 cubic inch motor, I’m using a Chevy big block 427 tall deck block 4.310 bore and 4.500 stroke, I bought 26cc dome pistons, use Brodix heads, either 345cc are 366cc, 119cc combustion chamber, I’m shooting for 1.7-1.8 HP per cubic inch, any help would be appreciated, thanks

[@MuscleCarSolutions]

Well, based on the information in the video, what did you come up with?

[@merritts3515]

Carburetors are very forgiving. And I've tuned a 750 on a low buck sbc. I wouldn't even try to make a 650 work on a big block. They'll only flow so much air, and because of that only so much fuel. But I'd rather be bigger for sure.

[@MuscleCarSolutions]

It’s all about the combination and the operating RPM. I’ve put 500 CFM carbs on big block yard dog trucks that operate well under 4000 rpm. Bigger isn’t better. It’s a very common mistake.

[@merritts3515]

@@MuscleCarSolutions that makes since. A big block that only idles could run on a 390 cfm carb just fine. Once you start to open up the throttle you reach a point where the engine will need more than 390 cfm. As you mentioned with efi. They offer up 1000 cfm. But you run smaller injectors. I agree there's a right carburetor size for every displacement, and what the engine will be used for. I've just been far more successful getting way too much cfm to work in a pinch. Than vise versa.

[@roywarren6275]

496 bbc. 6000 rpm, roller cam 250/258 @ 50.. 3500 stall. Single plane intake 373 gears. Carb recommendation, thx

[@MuscleCarSolutions]

So what did you come up with based on what the video taught you?

[@roywarren6275]

@@MuscleCarSolutions I came up with a 850, mechanical secondaries because of the cam and intake . Well.........

[@MuscleCarSolutions]

@@roywarren6275 I'd agree the intake can handle that, the cam can for sure and the CI of that big block sure can. How are you planning on driving it? Drag car? Street bruiser?

[@roywarren6275]

The car will be one weekend out of the month bruiser. 68 Camaro ladder bar set up. Like the reviews of the “QFT” carbs. Like the street Q but for better street use I like the QFT SS 850. Specs about the same for both carbs.

[@MuscleCarSolutions]

I think you made the right choice on the size. Sounds like a fun driver! Then again, big cubic inch big blocks are rarely boring.

[@KingJT80]

if i used the first equation, thats what id wanna use for a mechanical secondary i just multiply it by VE 1.1 and get the bigger carb BUT its vacuum secondaries. a double pumper flows way more fuel vs a vac secondary of the same size. freiburger and company tested a 750 dbl pumper vs 750 VS MS made 20+ more HP with no other changes other than the carb type so just up up in size on a street carb this all N/A pump gas 91-93 octane

[@MuscleCarSolutions]

The formula, no matter what is used, is going to be a ballpark result. This one is easy to understand and is a good starting point to determine what direction the user needs to go size wise to get the best CFM. Certainly a race application will look at race carburetors and not the VS models. Fortunately is a wide spread on sizes. Hard to get too wrong. The alternative is what I see time and time again. Someone talked them into putting way too much carburetor on their application. The street guys always seem to have the most trouble.

[@KingJT80]

@@MuscleCarSolutions yeah ive read about a lot of guys going for too much carb. i figured a 6500 RPM 302 with 4.10's and a 3000 stall and aluminum heads and about 10:1 a 600 dbl pumper would work in a 2900 lb car with me in it @ 3100+ mercury zephyr close enough i guess

[@MuscleCarSolutions]

Depends on what you’re going to use it for. Sounds like you’ve got it dialed in. I’d trust a 600 to tune through those things you mentioned and the aggressive driving that it’s built for.

[@KingJT80]

@@MuscleCarSolutions yeah I'd say it's gonna be "hot street" somewhat MAYBE a couple of track runs but nothing serious. Just want it to get up and go pretty decent for a fox body on the street

[@crackpotfox]

I'm guessing the 750cfm carb on my 305 low compression el camino is slightly oversized. It's a qjet the PO put on to replace the feedback carb it came with.

[@MuscleCarSolutions]

Probably way way too big.

[@marquisephillips1637]

I’m having my 5.3ls rebuild with a mild cam heads all that good stuff. Thinking of switching to a high performance carburetor. What size should I use. I think I have a 650 double pump on it now

[@MuscleCarSolutions]

What did you come up with after watching the video?

[@ezekielmoore4081]

I have a 94 Chevy c2500hd with a 5.7l with a automatic and 3:73 gear ratio I am planning on getting a edelbrock cam with a 204/214 duration @ .050" with a. 420/.442 lift with a lobe sep. 112° and some shortie headers with 2.25 exhaust pipes. I bought a demon 625 cfm, I did the math originally and came up with a 500 cfm but I figured with the mods the 625 would be better.

[@MuscleCarSolutions]

I’d say you bought the right size.

[@ezekielmoore4081]

Thank you sir I appreciate your reply, take care.

[@MuscleCarSolutions]

@@ezekielmoore4081 anytime!

[@88classic]

That's like a stock cam not really a upgrade cam

[@robertswick7654]

I ran your equation on a ZZ4 Chevy motor , 350 x5800 /3456 = 586.3 CFM carb. Chevy documents for the carb calls out for 750 CFM Holley. I have a 600 CFM double pump Holley carb. I am assuming the 750 must be jetted down and my 600 jetted up. Kinda confusing.

[@MuscleCarSolutions]

You cant tune CFM. It’s a fixed number. You can however adjust fuel and spark to help tune the engine to its full potential. Are you using this as a drag only engine? Any other upgrades of significance? Nitrous? Boost? Then maybe... and that’s a big maybe, a 750 would work. Only if it were a vacuum secondaries carb. Like what was mentioned at the end of the video in other details to look at to confirm the right size. What are you using the engine/car for?

[@robertswick7654]

No it’s not a drag vehicle, I have a 1965 El Camino . It’s just a street Rod. I have an appointment with RPM carburetor shop to get it tuned, but I watched your video and ran your numbers for curiousty. Chevy 750 carburetor was most likely for drag car. Thanks

[@MuscleCarSolutions]

Well a street car is a whole different story. How often do you see 5800? If you’re just cruising, not often at all. You may see it if you’re doing some more aggressive driving, but unless that’s a common occurrence, you’ll never use the CFM that carb delivers. With a 750 it’s going to be very rich pretty consistently. There are a number of other things to consider but in very general terms, it’s all about assessing how you’ll drive it and those factors that are unique to your situation.

[@dwilkes6]

@@MuscleCarSolutions I have a ZZ4 in a 29 model A that I just got. It has a 750 on it now but leaking and I was going to replace it. The motor has a performer RPM manifold and edelbrock mechanical fuel pump.Was told it was a stroker motor. But I'm not sure. I was wondering if you think a Edelbrock 600 or the AVS2 650 would be best? Just a cruiser hot rod. Just trying to get it running right to enjoy.

[@funintheshop1247]

400 small block bored 30 over with small cam. Got a 750 cfm and a 600 cfm amdni camt seem to get either one adjusted to get the stumble out when the throttle is hammered down

[@MuscleCarSolutions]

Well. Start with the CFM. Which best fits your situation based on what the video showed? Next if verify initial and full timing. Then verify proper fuel system set up. Then you can start tuning.

[@zx600e93]

Will a 750 (CFM???) Edelbrock for my soon to be machined /rebuilt 1970 472 V8 Cadi CDV (keeping engine as OG as possible and boring only)? I've been advised to go electric choke too, so will I need press. reg, and electric fuel pump too or can I keep my og mechanical fuel pump? Thanks for awesome Vid I think my calc for CFM = 601. [472 X 4,400]/3456= 601 This car will run. 91 gas, mostly cruzin to shows and with low riders, but want to drive say within 100 miles distance on freeway 70mph. Thanks again from Sunny SD, Cali. Cholo Clem

[@MuscleCarSolutions]

Go with the 650 AVS2 carburetor. Better choice for what you’re doing.

[@cutl00senc]

Since the 70’s, the math I’ve always heard was cid x 2= cfm in most street/strip applications

[@MuscleCarSolutions]

I suppose you could start there. Maybe those folks had different ways of thinking about it back then. For sure the parts were different. Fuel was for sure different. Less access to lots of cam grinds and cylinder heads. But like the common math problem of today, it leaves too many questions unanswered.

[@cuzz63]

Doesnt really work like that. You would be putting a 900cfm on a 454.

[@stuckinmygarage6220]

@@cuzz63 Based on the video(s) 900+ might work, believe it or not. It's situational. 👍☺ Re-listen.

[@cuzz63]

@@stuckinmygarage6220 I actually agree but its not as simple as 2x CID.

[@diagonalley1785]

I have an AMC 360 CID V8 5.9L with 5500 RPM. I am trying to get it street and autocross but I want it to be a little above average, I'm not sure what Carburetor will give me the tuning freedom to allow me to push my '78 Wagoneer from 0-60 in 11.9 seconds

[@MuscleCarSolutions]

That engine isn’t really knows for its high rpm capabilities. You’re really going to spend a significant amount of effort (and money) to get what you want. Why not swap in a mopar engine that would allow you to reach that goal at a fraction of the cost? Either way, you’re going to spend more time on intake, cylinder head, compression ratio, valvetrain, transmission/differential gearing than you are on carburetor size. That would be your last decision.

[@adampell1607]

Hi, love the content, I've got a 383 Chrysler stroked to 489, mild hyd roller cam and alloy heads, Thinking 750cc will be enough for street, auto 4 sp and 5500 max revs ?, thanks

[@MuscleCarSolutions]

@@adampell1607 that’s probably where I’d start but knowing the cam specs and being honest about how you want to drive it are the some big factors.

[@adampell1607]

Awesome, yep street car 99 of time. Cheers for the help👌​@@MuscleCarSolutions

[@MuscleCarSolutions]

@ then it will be a very easy size to tune for that application. 👍

[@brandonford7421]

What size carb and what type of carb would be best for a 4×4 off-road truck with a Ford 408W stroker? 6000 max rpm manual transmission 3.55 gears. The truck weight is about 5000

[@MuscleCarSolutions]

That’s a good one. As the mathematical answer falls at an uncommon number. So you’re using it as an off roader. You should have a cam profile and intake that is around idle-5500 rpm. If that’s true, then the off road 650 Edelbrock would be perfect.

[@ronnieyoung7510]

I have a 360 Chevy big camera 202016 exhaust for tens in the rear 4 speed to Chevy Malibu 78 I'm going to ask for a size cop should I put on it

[@jamesfitz1227]

If an engine is basically an air pump the engine is only going to flow as much air through that carb as the engine can injest. And the carb meters the air to fuel. So wouldn’t a oversized carb really not be an issue.

[@MuscleCarSolutions]

If it only flowed air then sure, that’s probably a good theory. But they also flow fuel and the bigger the CFM the more fuel they meter and the more raw fuel that gets dumped into an engine that’s not capable of using it is a big problem.

[@firetowngaming4306]

Great video. I’m new to this and I’m hoping you can give me some guidance. I recently bought a ‘70 c10 that has a sbc 400 with a th350 trans & a 373 rear gear. As far as I can tell the motor is stock. According to some forums I read my trans should shift at around 4500 at wot. When I do the calculations I come up with 520cfm without using the Volumetric efficiency. I’m looking at an edelbrock AVS2 carb in either 500 or 650 cfm. Would you go with the 500cfm if you were just using the truck as a cruiser for the most part?

[@MuscleCarSolutions]

Because of the cubic inches, I’d probably opt for the 650. Especially with that rear gear. But the biggest question would be, are you planning on any upgrades in the future? Headers, intake, better ignition, etc. if the answer is yes to any or all of them, go with the 650.

[@firetowngaming4306]

Not planning any engine upgrades. There are lots of other things that need attention. I can’t say for sure if I will do some in the future or not. That being said do you still think the 650 is the way to go? When it comes down to it I guess what I am wondering is how much the throttle response will suffer with the 650 if no changes are made to the motor.

[@cargeekscott1871]

Ford 302 bored 30 over manual going to use a t5 with 3.55 gears in a ford ranger. Looking for a torque cam and wanting to tow/haul with it and also just daily drive it. I was thinking a 600cfm would be great.

[@MuscleCarSolutions]

If you’re using a smaller duration cam that’s typically all in by 5000-5500 RPM, the 600 or new 650 AVS would work just fine for that application.

[@cargeekscott1871]

I'm thinking the melling 24110. Advertised intake is 282 and advertised exhaust is 298 with an operating rpm of 1,200 to 4,000. The factory cam is advertised intake is 283 and advertised exhaust is 273. Max rpm id go is probably 5,000 for either cam. And could you tell which cam would supply more torque at lower rpm?

[@MuscleCarSolutions]

@@cargeekscott1871 I’d need to see the specs at .50 to know which would be better on the low end side.

[@cargeekscott1871]

@@MuscleCarSolutions the stock is 186 intake and 197 exhaust and the melling 24110 is 210 intake and 211 exhaust

[@MuscleCarSolutions]

@@cargeekscott1871 that is a very mild cam. Should be all in by 5000 rpm. Should be just fine with your combination. Just know that the cheap cams are typically valvetrain noisy.

[@johnharvie4537]

Was wondering what you think of a 750 Holly 4 barrel on a 428 cobra jet Torino, with air ram, 1969 fastback

[@MuscleCarSolutions]

For the same reasons in the video, I can’t answer that question without a bit more info.

[@donbrown842]

Hi 454 Chevy 100 octane fuel in a Vdrive boat 6000 to 6500 RPM roller cam what do you suggest for Carb. thanks

[@jackreisewitz7219]

Why is the RPM not ÷ 2, as a four cycle intake stroke only comes every other revolution?? Never did it that way - always wondered why not??

[@markmccarty9793]

With dual plane intakes and modified vacuum Hollies I've ran 750 hollies on 302s to 460's! 50cc pumps and change the shooter size a 28 secondary on 302"s to 31 460's !! A 28 shooter works on 302, I use a 31 to 33 on everything from 351 to street 460. The bigger cams have low vacuum so use a light spring till it bogs and back off to the last one! It's not rocket science, and it's not expensive!

[@4739-g9c]

Pounds of air would be a way better calculation. We have math for fuel. X amount of pounds fuel per hr or minutes gives us x amount of horsepower capability. We also know that desired air fuel ratios are between 11-18 air to 1 fuel. So by figuring out lbs per hr fuel we can calculate air required then the last variable would be what type engine. 1cyl or 12 cylinder. Most engines come with plenty cfm it's merely the tunability of of carb from there. Those equations were made to sell carbs in the market

[@MuscleCarSolutions]

Those equations were made to give a far far less complicated target CFM. It’s not a finite science. If there were more sizes of carb available and a better result by drilling down to that level then yeah. We’ll leave the big math to factoring injector and pump sizes for the EFI world.

[@mathewruppert8682]

Thank you for the knowledge but I wanted to ask to be sure I have a 1978 Ford F250 super cab 4x4 with a 460 4000 rpm would probably be my max rpm I'm looking for fuel efficiency more than anything daily driver if you could help me pick a cfm that would be great I run maybe 85 or 87 from the gas pump

[@MuscleCarSolutions]

Well, you have the key components there. What did the math tell you? Something to keep in mind here. If you really want better fuel economy, and this is something you’re driving frequently, you’ll find those big gains in the transmission, not the engine. I did a video on how to get better fuel economy in a muscle car a few years ago to illustrate how that’s possible.

[@mathewruppert8682]

@@MuscleCarSolutions sounds good I'll find the video I have a C6 automatic transmission if that helps

[@stacetriebwasser6425]

Got a Ford 300 that i plan on keeping the internals mostly stock, just playing around with porting and cleaning up the factory manifolds, in your experience are the 1 barrels that came on these engines decent or should i ditch it for a smaller 2 barrel?

[@MuscleCarSolutions]

Boy I’ve had great luck with the 300s in the past. No kidding. I drove a cargo van from Dallas to KC with the factory one barrel zip tied onto the manifold. Somehow they vibrates loose and was stuck on the side of the road and zip ties to the rescue. Honestly unless you’re really make some big changes; cam profile, CR, you’re likely going to be ok with the factory carb. If you get into those areas, that’s when I’d look at a slightly bigger carb.