Volvo 740 Oil Pump failure.

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undefinedI have a 1991 740 Volvo 16 valve engine with 147,000 miles. At 145700 I reworked the head due head gasket failure. At the time I did not remove the oil pump.
After approx 1200 miles the Pulley bolt attaching the the oil pump to the pulley sheard off. As this pulley is driven by the belt that drives the overhead cams I bent 8 valves.
I replaced all vavle guides and valves.
I removed the oil pump dismantled it and cleaned it . I replaced the failed bolt and rebuilt the pump.
Rebuilt the engine and it was running fine until last Friday.
After 600 miles the oil pump/pulley bolt has failed again. Again I have lost valves due bending (only 2 this time).
The only explanation I have is
1. a foriegn object got stuck in the oil pump causing it to jam. When I took it apart this time I was careful to check for debris. Nothing
2. The oil pump shaft is worn sufficient to cause the gear to jam in the housing at temperature.
Has anyone out there ever had this before, if so what was the cause.
Any assistance would be appreciated.

posted by  stuwild

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