Probable Cause(s):
* End Of Stem Worn Or Rocker Arm Contact Surface Worn
* Worn Push Rods
* Broken Or Worn Valve Lifter
* Worn Lobes On Camshaft
* Not Enough Lubrication
1. End of valve stem worn or rocker arm contact surface worn:
If there is too much wear, install new valves or rocker arms. Check and make necessary adjustments as per Testing and Adjusting Section of the Service Manual.
2. Worn push rods:
If there is too much wear, install new valves or rocker arms. Check and make necessary adjustments as per Testing and Adjusting Section of the Service Manual.
3. Broken or worn valve lifter:
Install new valve lifters. Check camshaft for wear. Check for free movement of valves or bent valve stem. Clean engine thoroughly. Check and make necessary adjustments as per Testing and Adjusting Section of the Service Manual.
4. Worn lobes on camshaft:
Check valve lash. Check for free movement of valves or bent valve stems. Install a new camshaft. Install new valve lifters. Check and make necessary adjustments as per Testing and Adjusting Section of the Service Manual.
5. Not enough lubrication:
Check lubrication in valve compartment. There must be a strong flow of oil at high engine rpm, but only a small flow at low rpm. Oil passages must be clean, especially those sending oil to the cylinder head.