Lesson 1/Learning Event 1
which rests on top of the tappet and extends up to one end of the rocker arm. Notice that in this system the
valve clearance adjusting screw is located at the pushrod end of the rocker arm. A cover, bolted to the top of
the cylinder head, covers the rocker arms.
FIGURE 34. OVERHEAD CAM.
In the other method of operating the valves of the overhead valve engine, the camshaft is located on the
cylinder head. This engine may be called an overhead cam engine. In technical manuals, it may even be
shortened to read OHC engine. Rocker arms that pivot on studs are the only link between the valves and
cams. Valve clearance is adjusted by inserting shims between the cam lobe and the lifter.