Wear at the points of contact on a rocker arm is generally in the form of pitted, deformed, or scored surfaces. Wear on the rocker arm pads and end fittings is greatly accelerated if lubrication is insufficient or if there is excessive tappet clearance. Pushrods are usually positioned to the cam followers and rocker arms by end fittings. The pads are the rocker arm ends that bear the valve stem or valve stem cap. When the tappet clearance is excessive, the rods shift around, greatly increasing the rate of wear of both the rocker arm and the rod contact surfaces.
Worn fittings necessitate the replacement of parts.
Continued use of a poor fitting and worn pushrod is likely to result in further damage to the engine, especially if the rod should come loose. Worn tappet adjusting screws and locknuts usually make maintaining proper clearances and keeping the locknuts tight very difficult. Wear of the adjusting screws is usually caused by loose locknuts, which allow the adjusting screw to work up and down on the threads each time the valve is opened and closed. To prevent this wear, tighten the locknuts after each adjustment and check the tightness at frequent intervals. If the threads are worn, replace the entire rocker arm.