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.
For a street engine, the
RPM used should be the peak torque RPM.
For a race engine, the peak hp RPM should be used.
The following calculator can be used to calculate the header dimensions best suited to your combination. The input terms are below:
CID is given in inches.
Exhaust Valve Opening Point is given in degrees after top dead center (ATDC). Entered values should be greater than 0.
Peak Power RPM is the RPM value at which your engine makes peak power.