This calculator is for entertainment value only.
Not to be used in place of real testing.

For a more accurate calculation try Larry Meaux's Pipe Max.
His program is excellent and will provide a lot of info.
Pipe Max

Estimate RPM That Peak Horsepower Will Occur
Enter Head Air Flow in CFM (at 28 in. of water):
Enter Engine CID:
Input Head CFM and CID, Please

This calculator shows at what RPM peak HP should occur based on engine displacement. These calculations are for port work with no 'choke'. "Choke" is defined as the intake port with flow, but not adequate cross sectional area to provide real intake flow to fill the cylinders. To figure your 'choke' - Choke Calc