Inliners International Forums General Discussion Hi Performance GMC/Old Chevy Single Headre Design Questions.

Thanks for the Wallace Racing reference. I used their header equation. I am not sure about peak power rpm or volumetric efficiency numbers but I used these inputs for my 302 GMC: stroke =4.0, Bore = 4.03, Ex. Valve dia. = 1.6, Ex. Valve opening pt. = 61 BBDC., ex. valve duration = 264, ex. Valve centerline = 109 BTDC, peak power rpm = 4,000, Vol. Eff. = 80%. Cam is an old Isky E-2.

Here are the equation outputs: header length = 55 in., tube I.D. = 1.38 in., collector I.D. 2.74 in. This equation is for dual header design with 2 collectors.