About 5 years ago the good running '54 235 in our '40 Chevy suddenly began making a noise that I could not identify. It sounded like something hitting sheetmetal, like maybe the oil pan. I thought something had been left inside the pan, for the crank to hit. Maybe like part of an oil pickup screen, from a previous rebuild. I could find nothing. I checked everything else inside the engine for problems, and found nothing. The crank and all bearings look great. The pistons and rods checked out fine as well. The cross hatching was still there in the cylinders The cam and lifters were beautiful. Timing gears were obviously replacements.
Now I've located a '51 Chevy sedan delivery that I hope to buy, and would like to put the 235 back together for it. I guess I'll start with the block and go over everything with a strong light and a magnifying glass and put it together. I hate to think that it could have been the tailpipe hitting the frame but that's about the sound it made.