The Edelbrock #5862 Sure Seat Valve Spring for Big-Block Chevy 396-402-427-454 V8 O.E Cast iron cylinder heads are made of highest quality spring wire and precision wound to close tolerances, our Sure Seat Valve Spring sets are for use on original equipment heads when installing Edelbrock Performer-Plus, Performer RPM and Torker-Plus camshafts. These are the same high-performance springs used on Edelbrock Performer and RPM cylinder heads. For camshaft warranty compliance, use only the springs recommended by Edelbrock for each camshaft application.