Exhaust Header Length Computation By Bowling &
Grippo
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
am not sure 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 - go ask Ed. However,
the calculation is still interesting, and may help you get into
the ballpark.