Water-Cooled VW Performance Handbook

Calculate intake and exhaust valve sizes

If you know your engine’s bore, stroke, and rev limit, you can calculate the ideal sizes for the intake and exhaust valves. Note that this is for two-valve cylinder heads.

Bore mm
Stroke mm
Maximum RPM   mm
Intake valve mm
Exhaust valve mm

For example, a 1,588 cc engine (bore of 79.5 mm and stroke of 80 mm) and a rev limit of 6,000 RPM should have a 36.4 mm intake valve and a 31 mm exhaust valve.

This calculator uses the following formula:

Valve diameter = √((rpm × stroke × bore²) ÷ 2,286,000)