NO DISCOUT ON CUSTOM VALVES

According to Jim K research undersize exhaust valves make better power than std 40 or oversize 41mm valve by reducing over-scavenging. Several customers have been successful , so we have produced these undersized valves by popular demand without our own testing.

• The 1mm smaller stem allows better flow.
• 20% lighter (21 grams) than the 1mm oversize 4.5x 9mm stem valves. This is worth power since the exhause seat pressure can be reduced.

• For more information on valve sizing and cylinder head performance buy a copy of the Jim Kartalamakis book advertised at the top of this section.

• NOTE: We can special order any valve size you decide is best for your engine.