Holley cfm selection

[Right hand drive]

Don’t know if this has been done to death or rarely ever raised. How do you guys decide on cfm for your application?

I remembered this chart at the back in the technical section of a 1987 Holley catalog:



Very different from the mathematical formula that has been around a long time - ci x rpm x VE / 3456 = cfm. Another version being ci x rpm x VE / 2820 = cfm

Thoughts on both methods above and how do you hone in on cfm for your combo?

Discuss.

[jmarkaudio]

That's old, doesn't account for newer engines efficiencies, higher stall converters, vehicle weights, gear ratios...

[Right hand drive]

[jmarkaudio]

A chart isn't realistic, too many variables. That chart was designed for the average street car 40-50 years ago. And then you have manifold designs, booster types, I find with annulars you can put a bigger carbs on and still get great throttle response.

[Right hand drive]

[novadude]

I assume this chart (and the formula) is based on WOT. Do you give up part throttle response running a 750 vs a 600 on something like a 400 ci mild street engine? Would the difference be something the average driver could perceive?

[hysteric]

Here's Holley's latest recommendation:



Looks like the recommendations are very close to the original. Question then might be do the HP's flow more air and how much?

[Right hand drive]

[hysteric]

[Right hand drive]