318 carb requirements
 

i found a formula for figuring out the cfm requirements for an engine. the formula was

Cubic inches x maximum used rpm / 3456 = ideal cfm.

Ideal cfm x voulumetric efficiency = actual cfm

so i put my 318 into the equation. maximum hp is at around 4000 rpm so i went with 5000 rpm cause thats the highest i ever had it. Mopar muscle magazine said that racing only vehicles had a volumetric efficeincy of 100%
a high performance street/strip was about 90-95% VE
a stock to slighly modded motor runs at 80-90% VE


im going to assume with the 302 heads that i gasket matched, the headers, and a 4bbl intake manifold that im running around 87% VE

318x5000=1590000 1590000/3456=460 ideal cfm
460x.87=400 needed cfm.

in the magazine article they said you dont want to go less than the needed cfm but i figured i need between a 390 and 450 cfm carb for my application. I was wondering if anyone knew of a carb that came stock on something that i could use instead of shelling out 300 bucks for a new one. I was shocked to see that i needed a carb this small but i assumed 600 or 650 was too big.

Put a 600 cfm Carter/Edelbrock on it, & forget it. While the old cfm formula makes sense, it rarely works in the real world. You can get a manual choke 600 Edelbrock on sale for around 200 bucks, if you're really on a budget, get a used one & rebuild it.

it just seems like 600 is way too big. ive talked to other people that said that when they put 600's on they got sluggish

carter/edelbrock has a 500

i was thinking of the edelbrock 500 with manual choke but wasnt sure if that was going to be too much for my engine