Slightly strange head flow question.

Rat Patrol said

Maybe this will help

XS282S Cam - .520/.540 lift @ .50, 244/252 @ .50 duration, recommended 2500-6500 rpm

If I have access to two two pairs of identical Edelbrocks (springs valves etc)

- one set flows 260cfm at .550, the other 290cfm at .650,

For arguments sake, lets say both display "healthy" low-mid lift figures also.

Which should I use and why?

Assume the cam, M1 SP, 800cfm carb and everyting else will not be changed.

Click to expand...

on the dyno....the head that flows more from .0001 to what ever the actual valve lifts will make more power, given all is the same otherwise.
If they both flow the same throughout but one go's to a higher lift to make it's peak....the one thing I can say about that is port distribution/csa,..hmmm glug glug.. not gonna side track yet...

But the 1st line answers you're question.
The why is obvious.
you arent opening the valve to .650 lift or even close.

heads flows x amount peak at .600, cam lifts only to .540, then figure geometry losses and intake tract losses, mainly you arent lifting the valve to the .600 peak.....you are only gonna get .500'ish flow, if you open the valve to .600....then you'd see that flow...