The Edelbrock Sure Seat Valve Spring is made of highest quality spring wire and precision wound to close tolerances. The Sure Seat valve spring is designed for use on original equipment heads with Performer-Plus, Performer RPM and Torker-Plus camshafts. The basic purpose of a valve spring is to close the valve while also ensuring that the valve train stays in contact with the cam lobe. Good valve springs provide adequate seat pressure to allow a tight fit between the valve face and the valve seat to seal the combustion chamber. The valve spring seats provide protection for aluminum heads and locate the valve spring to prevent it from moving around at higher engine speeds. Valve springs require checking the clearance between the rocker arm and the retainer before starting the engine. The valve spring rates and camshafts must be compatible to avoid valve float and severe engine damage.