GM Service Manual Online
For 1990-2009 cars only

Inspect the following areas:

    â€¢ Inspect the valve rocker arms and ball at the mating surfaces. These surfaces should be smooth and free of scoring or other damage.
    â€¢ Inspect the valve rocker arm valve pushrod sockets and valve stem mating surfaces. These surfaces should be smooth with no scoring or exceptional wear.
    â€¢ Inspect the valve pushrods for scored ends or bends.
    â€¢ Inspect the camshaft and crankshaft sprockets for wear
    â€¢ Timing chain for teeth that are no longer concentric
    â€¢ The valley between worn teeth
    â€¢ The key and crankshaft keyway for wear
    â€¢ The timing chain for binding or excessive wear