Well, I had an engine rebuilt a few tears ago and never started it but from time to time I would turn it . It was always very tight , Well the other day I finally started up the engine and it was running very smooth and quiet. I have started and stopped the engine a few times maybe total running time 1hour. Today when I started it cold there was a low end knock that went away after a few minutes as the engine warmed up. I decided to take a look at the oil when I drain it out the oil was black like it had 5000 miles on and old engine . This is a newly rebuilt engine with 1 hour on it sorry if I am repeating myself. I was amazed how dirty the oil was examining the oil further it had a silver sheen to it and when I drained the pan I found small bits of what I am sure is bearing material . I am sure that the machine shop did not clean the oil passages correctly its evident how dirty the oil was with no run time .  Now the question , since I have really no run time on the engine can I drop the pan install new rod bearing and hope the crank has not been damaged .  It only knocks when it cold as soon as it warm its sounds great . This guy screwed me because I was charged for a new water pump and as soon as the engine was started the leaked and I had to replace it . The impeller on the pump was old and pitted so I knew it was not changed . I was charged for an oil pump but I have my doubts about that also . So what do you guys think can I get away with a new set of rod bearings and a new oil pump. Cheer me up . Thanks in advance .