Valve springs are mechanisms that serve to close the valves. Valve springs are made of highly tempered round steel wire that is wound in a spiral coil. Only a small percentage of the spring force is required to keep the valve tight on the valve seat of the head. The majority of the spring force is used to keep the pushrod (fig. 4-1) or the rocker arm (fig. 4-2) in contact with the cam while the valve is being opened and closed. This force of the valve spring prevents the bouncing or fluttering of the valve that would otherwise

Figure 4-2.Valve operating mechanism with valve bridge (General Motors 16-278A).

occur from the rapid motion of the opening and closing of the valve at high speeds. So that the spring can have sufficient force, it is always compressed when it is installed. (It is further compressed, of course, whenever the valve is opened.)