Designed for 1997 & later GEN 3 & 4 LS1/LS2 Chevy engines including 4.8L, 5.3L, 5.7L & 6.0L. All E-CNC Cylinder Heads feature fully CNC'd intake ports, combustion chambers and exhaust ports for improved air-flow. Dyno tests proved these heads are capable of 457 hp & 438 ft-lbs. of torque. High-quality conical beehive springs are secured with steel retainers and valve locks for performance up to .600" valve lift. Match with any one of Edelbrock's LS series intake manifolds and camshafts for a dyno-proven performance combination. Rocker bolt kit 350-8597 includes 8 rocker bolts that are shorter than stock to prevent the bolts from protruding into the intake ports. E-CNC 215 head is 50-state street legal.