Yesterday I was taking a Combat engine apart to rebuild for a customer. While doing that I inspect things to see what I need to buy, service, or fix. This engine has over 78k miles and was apart once when almost new for a bad piston and never since.
When I took the oil pump off it turned very freely, already means worn, but then I noticed that when I looked into the return port turned the drive gear, it appeared that the gear was not turning and was broken. Took the pump apart and it turned out that the gears were all turning and there were no broken teeth but there was a chunk of metal stuck in that port that looked like the end of a Woodruff key. Also, the gear nearest it had small marks from hitting that metal.
Since the oil pump bolts were not staked and there was nothing to tell me otherwise, I assume it left the factory with that metal in that port. The metal blocked about 60-70% of the passage so the pump could work. The metal came out easily by pushing inward once the gears were out of the way.
It is clear that the metal could not go through the pump, so it was in the pump when the pump was assembled.
