How To Build An Engine - Build Your First Engine

Coil bind is the point at which the valvespring wire compresses against itself and becomes solid. On the JMS valvespring tester, a stock Chevy spring goes into coil bind at 0.510 inch lift. That'd be a parts-breaking disaster with our 0.540-lift Isky cam.

Valvesprings must be set at the manufacturer-specified installed height. For our Isky 305-DHS single springs (with surge dampers), that's 1.750 inch. This delivers 125 pounds of seat pressure and 240 pounds at the 0.540-inch full lift value. Coil bind doesn't come on until 0.625, leaving us a safety margin. Because the heads originally featured exhaust valve rotators, the exhaust valvespring seats are factory-cut 0.060 inch deeper than the intake seats. We compensated with 0.060-thick spring shims to reach the 1.750-inch installed height and 125-pound seat pressure on the intake valves. CHP