Two-barrel vs. Four-barrel CFM Ratings

six packs were rated lower because the draw across 6bbls was weaker than across 2 or even 4 bbls. I think Vizard only rated the 340 six pack at like 780 due to the fact that the smallish 340 just could not pull more air through them. The 440s were rated higher simply because they could pull more. Dont confuse Carbs CFM to what they can pull on your motor. A darn quadrajet will run a slant six nicely cause itll only pull what it can ecen with the larger secondaries as they are variable.