[A Snake]

This direct from the Holley site.

How To Calculate CFM:
Engine size (CID) x maximum RPM / 3456 = CFM
CFM @ 100% volumetric efficiency

(Example: 350 CID x 6000 RPM = 2,100,000 / 3456 = 608 CFM)

Approximately 608 CFM would be required for this engine. However, most Street engines are capable of achieving only about 80% VE; a modified street engine with ported heads, headers, intake and carburetor can achieve about 85% VE; a fully modified race engine can achieve 95% or greater VE. The CFM number arrived at with this formula must be factored by this percentage.

As can be seen in the above Holley information, it doesn't take near as much carb as you think. Actually, if you run out the formula for a 289 or 302, you'll find that 500CFM is a lot closer to what will really work right with a mild engine.

I tried the big carb(600CFM) trick on my '64 El Camino with stock 283. It didn't like it at all. Nail the gas at under 3000RPM and it just bogged.

Get some compression (11:1) stiff cam (.550@.050" 108 degree lobe centers) low butt gears (3.73:1) do the head work and a 600 or 650 will probably do a decent job on a 302.

I will add the Holley part to the new FAQ forum Brent and Ron are starting.

Al