You will probably hear them called valve tappets or vale lifters. In the L-head engine, the followers directly contact the end of the valve stem and have an adjusting device in them. In the overhead valve engine, the followers contact the pushrod that operates the rocker arm. The end of the rocker arm opposite the pushrod contacts the valve stem. The valve adjusting device, in this case, is in the rocker arm.
Many engines have self-adjusting, hydraulic valve lifters that always operate at zero clearance.
Valve operating mechanism for an overhead valve engine. Figure 12-26 shows the operation of one type of hydraulic valve tappet mechanism. Oil under pressure is forced into the tappet when the valve is closed. This pressure extends the plunger in the tappet so that all valve clearance, or lash, is eliminated. When the cam lobe moves around under the tappet and starts to raise it, you hear no tappet noise.