2003 300ex broke a cylinder sleeve so bottom end got trashed, picked one up from a guy, shined a light inside thing was 100% spotless. So I put it in after swapping some little stuff from what was good of my crap one, assembled my top end threw some oil in and it fired right up. Lightly reved it up and on its way back down to idle seemed like from the lower end was a slight knock. Reved again, lighter but still there, again and it was still there so I shut it off. Fired it up again ten minutes later and I didn’t hear it but I didn’t let it run long. Hoping to get it out tomorrow but not sure what the deal is. Really not looking to trash this bottom end. Beginning to get tired of working on it… Lol