GM Service Manual Online
For 1990-2009 cars only

Tools Required

J 8520 Camshaft Lobe Lift Indicator

Inspect the following areas:

   • 
Object Number: 11481  Size: SH
  • Inspect the valve rocker arms and ball at the mating surfaces. These surfaces should be smooth and free of scoring or other damage.
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  • Inspect the valve rocker arm valve pushrod sockets and valve stem mating surfaces. These surfaces should be smooth with no scoring or exceptional wear.
  •    • 
    Object Number: 65453  Size: SH
  • Inspect the valve pushrods for scored ends or bends.
  •    • 
  • The camshaft and crankshaft sprockets for wear
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  • One edge of worn teeth or that are no longer concentric
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  • The valley between worn teeth
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  • The key and crankshaft keyway for wear
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  • The crankshaft timing chain for binding
  •    • 
    Object Number: 35243  Size: SH
  • Measure the camshaft lobe lift.
  • 0.1. Position the J 8520 with the ball socket adapter on the valve pushrod. Be sure that the valve pushrod is in the valve lifter socket.
    0.2. Slowly rotate the crankshaft until the valve lifter roller is on the heel of the cam lobe. The valve pushrod will be in its lowest position.
    0.3. Set the J 8520 on zero.
    0.4. Slowly rotate the crankshaft until the valve pushrod is raised fully.
    0.5. Compare the total lift shown on the J 8520 with the specifications.
    0.6. Remove the J 8520 .