The old engine had a bad knock, and it turned out to be a rod bearing knock. I removed the oil pan from the old engine and the oil was full of small metal fibers that were once rod bearing
Btw, I started the new engine today !!!!
it looks and sounds great. It was dark when I finished, so tomorrow I'll take a good long look at it and see if anything'* wrong. Amazingly it started right up, only a second or so after turning the ignition key for the first time. The only problem so far is that I don't have an oil pressure reading, but I saw that one coming - I'll probably need a new (or used) sensor.
I'm still amazed at how smoothly it all went. I never thought I was up to replacing an engine