[Cam]

I think you are on the right track. When I took the intake manifold in that I bought from you to have sonic cleaned, the guy that runs the place (Robbie) told me that it may take off some of the powdercoating. I told him I didn't mind, as looks took a back seat to performance and reliability. He said that was the right decision, because he could not count high enough to tell me exactly how many cars he had done machine work for that had the owners lose bearings due to not cleaning all the glass beads out of powdercoated parts.

This would explain the bearing loss in your car, just as YT has suggested. It could explain why you lost combustion in the last shortblock as well, since the glass beads in the intake could easily make their way into the combustion chamber and do irreversible harm very quickly. Good luck with your rebuild.