hese heavy duty single valve springs were developed together with the JPM MS230 cylinder heads but can be used on every other Type 1 (or with some modifications on Type 4) cylinder head.

They are made out of shot peened, heat treated OTEVA 90 material, a spring steel also used in NASCAR engines. The kit contain eight valve springs.

inner diameter: 23.6mm

outer diameter: 32mm

spring pressure at 39.6mm install height: 50.4kg

spring pressure at 25.4mm: 103.3kg

compressed height: 20.4mm