540milotalon

This is a V6 Buick actually but I really could use some suggestions. A friend had an engine, a high mileage ( over 100K) but good running engine installed in his '78 Buick. The guy that installed said he had to change pan from original engine to donor engine, and also said there was plenty crud in engine lifter galley etc.

Besides changing pan he removed some or all oil and saved and mixed with trans fluid supposedly to "clean" the engine out. This engine has been rolled around, pressure washed at a car wash and then started and drove home, when I was called for my two cents worth opinion the lifters were clacking terrible. I had the owner change oil and filter and noise continued so we hooked up a remote oil pressure gauge and NO oil pressure at all.

Question, finally you are thinking, after removing the front cover and tearing down oil pump and finding it pretty good as far as tolerances, could all this screwing around have caused a loss of prime to the oil pump which it never recovered? Could I reassemble a pump that shows well except for some mild scoring, and pack with vaseoline and expect it to pick up prime and work?