When 850 were as big as it got… LOL!!!
NEVER put a 750 on a 318........
- Thread starter 318willrun
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955 converted IIRC
How's that?
Ironracer
Gearhead
Seems to be a Workin" Deal on most of mine, over the years...
Not in the metering block/plate, just in that other than the earlier 3310(-1), almost all 4150's were double pumpers, except the line of SA's when they appeared....My mind was processing a response to 2 posts at once, lol..
Problem is they way carbs are rated, if your engine displaces 500 cfm of air at peak power that will be how much your carb will flow no matter if it's labeled a 650 750 850 or even a 250 they will all flow the same just there will be different amounts of restriction aka hp loss.
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Ironracer
Gearhead
YESSIR!
Rat Bastid
Dunamis Metron
All 4V carbs are tested at 20.4 inches of water. IIRC that is 3 inches of Mercury. 2V carbs are tested at about 10 inches of water which is 1.5 inches of Mercury.
You can 850 CFM through a 250 CFM rated carb by running the test pressure up.
The biggest mistake in running a bigger carb than the math calls for is not getting the booster correct. You can run a much bigger carb if the booster is carefully selected and not lose a single HP down low and gain from the middle all the way up.
Thats the real question is depression you want to run at full throttle not how much cfm.
I don't know what a restrictor plate flows but it's lot less then what a nascar engine needs, the air still gets minus the pumping loss hp cause of the restriction. My cousins late model pulls to 6500 plus through a two barrel.
Actually it's the other way around, but 2V-3.0" & 4V-1.5" are typical, conversion is sq.root of 2; 1.4142. Going "too big" just presents more tuning challenges, but will outperform too little if You've got it right for sure.
Cam & compression makes that possible, NOBODY chooses that strategy, long aggressive cams give more time & get the port flow up & sustained so they gasp as much as possible. Then You squeeze the poop out of what You manage to get in there. Time-bombs in NAPCAR prompted the rules for locking up the engines & shocks they qualified with.
Rat Bastid
Dunamis Metron
Lol! Been there! 850 thru' a 250 = train whistle, lol!
cudavert
DARTAHOLIC
"You'll lose your lower end!"
"You'll drown it in fuel!!!!!!"
"The computer chart says... cfms's!!!!
"Blah Blah Blah BLAH !!!!!"
I've heard it all, but the wind is out of my sail to continue the beat. I simply walk away. I say "ok", then smile. I will charge to explain it anymore. LITERALLY! You will PAY me before I go rounds again and explain it to you. LOL
Shelby, now there's a name. A recognizable name. A name that's tied to performance. What did he know?? Obviously, not much!! Because he put over 700 cfm Holleys on 289's. Yes, if you bought a Shelby 289 Mustang, you got a over 700 cfm Holley.
Yes, those 715 cfm "Lemans" vacuum secondary carbs may not have been optimal, but the fact that they're vacuum and not a DP kept things civilized. What is the cfm rating on the ol' 1987 318 Dodge diplomats' quadrajets? Or how does 1350 cfm on a 440 6-pack's trio of Holleys work? It just DOES!
dirty white boy
50 yr old Juvenal delinquent
my J headed 318 with wolverine cam, wealiend intake, high com pistons loved the 750dp really woke it up alot compared to the carter avs!!!
I got tired of rebuilding them all the time to keep them running good. Friends raced Super Stock and Stock, kinda opened my mind to what was possible. I stopped reading magazines and started listening. A friend was racing a 396 in a late 60's Chevelle 4 speed and was using a 850 DP Holley. He was running real slow times, so I asked him if he had the original Quadrajet. He did, so I spent a day doing it up right. Next race day we went to the track and he had so much low end power he shredded the clutch right off the line, first run. Well, he blamed me and the Quadrajet and put the stupid Holley back on. He continued to run slow. I'm not saying a Holley won't run good or make more power, but for me, they are not worth the aggravation for little to no gain. Thermo-Quads are amazing.
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I’ve been saying this for — EVER!
But yet! Some people say there engine only consumes *** of CFM on the dyno, so there’s no reason to use a bigger carb. I give up, run what ever the help ya want, just don’t ask my opinion on it.
Same as above! But I’ll add, it’s also amazing how well a factory intake offering will do as well. I’ll suggest it when the combo is right for it, where the focus is driving the car on the road and rpm’s on the highway or down the local neighborhood are low, there ideal. A lot is where the car/engine live and what your doing with it.
See posts #27 & #36...
thesiren74
Well-Known Member
If you can find a good one probably work for little while.
IfItsGotWheels
XS Tech-Anything worth doing, is worth doing in XS
I'm using a 750CFM C&S Aerosol Billet Carb on my 273. Goes like a scalded dog.
650 is perfect. why bother with a 750 on a street/strip 318. because you can I guess.
Two Edelbrock 500 AFB style carbs on my 340 - smooth as silk once it warms up, but again (as has been said here more than once) - air demand secondaries.
Exactly. It's all dependent on the combination and the type carburetor(s) used.
I just always had to try different things. I did not care what anyone said. The difference is between a 600 and a 750 was a lot more than noticeable, and I was running a 273.
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