Head flow and power differences question / discussion

coloradohill said

I am curious how much difference does let’s say 30-40 cfm of head flow make in HP.

Example: N/A small block 416 cu. 11.5 / 1 +/- compression

With a set of heads that flow 325 +/- compared to heads that flow 293 +/-

Everything else on the engine would be the same,intake,carb(s), cam,headers,ect.

Will the different heads be noticeable driving on the street or on a dyno only?

(edit)
What I am really trying to find out is, is there such a thing as too much flow and after a certain number, does the power curve go flat ? Or, is it always best to have the highest flowing heads available?

Let me know your thoughts and if I forgot mention anything.

Thanks in advance.

Click to expand...

Depends on application. Will this be a mostly hot road engine, a more track oriented engine or something along the lines of engine masters where the dyno rules. Track and dyno would be closer as low RPM response is not a factor. With street use in mind throttle response and lower RPM torque are the major concern. In this cituation the smaller heads are probably a better choice.
Max flow is good for street racing bragging rights (basically playing bullshit poker). What matters is port density and port efficiency, which contribute to cylinder filling. A smaller port contributes to higher airflow speed which helps fill the cylinder after the piston starts coming up on the compression stroke, but before IVC. The larger port contributes to lazy airflow and lower swirl. In a race engine at higher RPMs the larger ports should tend to more power.