Loose Wrist Pin In Rod

[damnyankee36]

What would cause a wrist pin to come loose in the rod? The engine developed a knock and upon tear down I found that the wrist pin had moved back against the cylinder wall and gouged two grooves in it. It's a stock build with 9.5 pistons and a mild cam. The engine has 1,000 miles on it since a complete rebuild.

A little background:

There have been two sets of pistons installed recently. The first set was during the first rebuild, 7,000 miles ago. The second set was after the engine overheated and the engine rebuilt again. The overheating caused piston and cylinder scuffing on two cylinders. The majority of the damage was with the same cylinder as the loose pin. The adjacent cylinder also had a little bit less scuffing.

I'm thinking the overheating had something to do with it. I'm wondering if the machine shop should have detected a little bit less force required to remove the damaged piston. I'm sure if the overheating did in fact cause the loose pin, it should have been noticed then.

At this time, the pin is loose enough to be pushed out with light tapping.

Any ideas? Thanks!