I just rebuilt my 4.0 1997 Wrangler, and I heard knocking so after I dropped the oil pan, I found I had a spun rod bearing, and the main bearings had significant wear. What could have caused this?
The rebuild included new the block bored .030 over, honed, line honed, new camshaft bearings, freeze plugs, crank ground, all new crank bearings, new pistons, lifters, reconditioned rods, valve job, etc. Is this something that machine shop could have done? I didn't plastiguage any of my bearings. But, they installed the crank. I did everything else.