Valve springs are mounted between sup-ports. These supports, commonly referred to as SPRING SEATS, are located at the ends of the spring. The LOWER SPRING SEAT may be simply a recess in the top of the cylinder head, or a steel washer that rests on top of the cylinder head, and is shaped to fit the bottom coil of the spring. The UPPER SPRING SEAT, called the SPRING RETAINER, is a steel washer that is shaped to fit the top of the spring. The upper spring seat is attached to the top of the valve stem by removable fastenings commonly known as valve keepers.

Valve Keepers

A widely used type of valve spring retainer is provided with a conical recess in the upper seat. The valve stem is locked in the recess by means of a conical split collar, called a LOCK or KEEPER. This collar fits around the stem and into one or more grooves turned in the valve stem (fig. 4-2).

Valve Rotators

On some engines that are subjected to long periods of idle or light loads, valve rotators may be used to keep the valves from sticking due to combustion deposits (carbon) forming on the valves. Valve rotators also serve to extend the life of the valves and valve seats by ensuring an even distribution of wear on the valve stem and valve guide. Without rotation, the combustion deposits that form on the valve stem, face, and seat would be cleaned off on one side only. Standard valve spring seats allow rotation but do not assure it. With controlled rotation, carbon deposits are cleaned off all around the valve stem, face, and seat. Valve rotators may be installed below or above the valve spring according to design requirements.