Originally Posted by JiMerit Boltr#43
That said, a friend went with this carb on a 300 ci inline Ford and found it was to small, moving on to 500 cfm I believe.

???

Race or street?

CFM at 100 % volumetric efficiency = (CID x RPM) / 3456

Rewritten RPM = (3456 x CFM) / CID

Or, for the 300 CID Ford

400 CFM is sufficient for 4608 RPM at 100 % VE

Or at 90 % VE 5120 RPM

I had a 400 CFM on our 300 CID, and it was a bit large, but still worked OK. The secondaries never opened in 4th gear.

Jon.

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