Exhaust Header Tube Length Computation By Bowling

The following "empirically" determines the best header length to use for a given tube outside diameter, CID, and maximum engine RPM. The equation I am using is from the company "Hedders by Ed" and I do not know if this applies to differing cylinder configurations (I am assuming 8 cylinders, 4-to-1 collector), and if this is for open headers or a free-flowing downstream exhaust. However, the calculation is still interesting, and may help you get into the "ballpark".

Program Inputs:

Header Tube OD (inches):

Engine Cubic Inch Displacement:

Engine Maximum Revolutions Per Minute (RPM):

Press this button to submit a computation:

To reset the form input:


The following equation was used in the above calculation:
BestHeader = (CID * 1900)/(rpm_max * tube_od2)

Bruce Bowling
Bowling Superior