Wallace Racing
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These formulas are from A. Graham Bell's Performance Tuning in Theory and Practice
or Philip A Smith's Scientific Design of Exhaust and Intake Systems.
The following calculator can be used to calculate the header dimensions best suited to your combination. The input terms are below:
Exhaust Valve Opening Point is given in degrees before bottom dead center (BBDC). Entered values should be greater than 0.
Engine Speed or Peak Power RPM For a street engine, the RPM used should be the peak torque RPM. For a race engine, the peak hp RPM should be used. .
* Exhaust Port Length - Take distance from roof of port to exhaust valve seat + distance from floor (short side) to the exhaust valve seat then divide by 2
Pipe Thickness - Wall thickness is assumed to be .050" and result is O.D. (outer diameter)