Made of highest quality spring wire and precision wound to close tolerances, our Sure Seat Valve Springs are designed for use on original equipment heads with our Performer-Plus, Performer RPM and Torker-Plus camshafts. The #5900 Series valve springs are designed for use with OEM valve rotators. To keep your warranty valid, use only the springs recommended by Edelbrock for each camshaft application. Valve Spring Kits contain non-rotator valve springs, retainers and matching valve stem locks. See Application Guide below.