The main criteria for your or any engine for the purpose of carburetor CFM is the cubic inches. Talked to the guy at Hot Heads and he said that he has a 331 Hemi with their aluminum heads, and high rise 4 bbl dual plain intake and he recommends 500 CFM carburation based on their dyno testing. I'm building a 331 55 Chrysler with 10-1 pistons, mild street cam, mild head work, dual plane high rise and headers. I asked about using a 600 Holley for dyno testing and maybe use afterwards and he said the 600 would be too much. Recommended a 500-550 cfm. https://www.inchcalculator.com/carburetor-size-calculator/ The Hemi engine is such a large impressive looking engine and it's hard to deck it all out in chrome and have a small 2 or 4 bbl carb sitting on top when the hood is up. Dual fours or other multi carburation setups just look right on the engine wither they hurt performance or not. Most of the people running a early Hemi in a period correct hot rod do so for the looks, not the performance.
How many people know the Volumetric efficiency of the engine? And unless your racing with a tach that can be checked how much is max RPM on the typical engine? One "rule of thumb" method is to double the CID & the multiply by .8. 331X2=662. 662X .8 = 529 CFM .
I have a '54 331 bored .060 with 12.5:1 pistons, an Engle roller tappet cam and other ***orted goodies in my dirt modified (avatar). I have run a variety of intakes on it from a stock 4 BBL to 4 in a row 97's and everything worked fine for vintage racing except the 4 BBL. Right now, I'm running 2 large-base 2G's adapted to a Weiand dual quad manifold (mainly for looks). Truth be told, the best the car ever ran was with a 500 Holley dirt track two BBL adapted to a the stock 4 BBL manifold, but it didn't look right. I do have the rev limiter set at 5500 RPM (I have a LOT of money in this engine and this is exhibition racing), so I'm sure that has a major effect on the overall performance, but I think it shows that 500-550 CFM is probably enough on the street.
I've run the 3x2 Stromberg 97's (SBC), 2x4 edelbrocks (Nailhead 401) and the single 4bbl. Of all the setups if you are going for reliability I'd go single 4bbl. If you want cool factor, go 97's with the frog mouth breathers. Never tried the inline 4 carbs, sounds like a headache.
6x2's compared to single 4 bbl. Hemi Induction Shootout: Does Retro or Modern Make More Power on a 354 Hemi?
This brings out a couple of thoughts. When I was in my late teens, one of the local guys had an early fifties Pontiac coupe with an Olds Rocket in it (any easy swap if you used the Hydramatic). He ran 6 twos with the aforementioned "frog's mouth" scoops, with their insides painted bright orange. It had a big rake and he didn't run a hood and when you saw that thing comin' at ya', it was COOL! Also, for a while I ran 4 inline 97's on a Weiand manifold on my dirt car. It ran fine, but for some reason, the carbs got messed up and I had to rebuild them every season. This got a little old after a couple of years, so when some guy made me an obscene offer for that setup, they went down the road.
The Jalopy Journal
