This one has me scratching my head a bit... My dad's tractor developed a bit of a knocking sound last spring, so I pulled the pan thinking it was bottom end bearings, as with the stethoscope, the bottom is noisy. I plastigauged all the mains and rods, and they all checked out ok. The oil pressure is around 60 lbs at idle, and I went ahead and adjusted the valves since they hadn't been done for since he put the motor in back in the 80's... This motor has never been torn down likely since it was built, and when I listen with the stethoscope, the head area and middle of the block are pretty quiet, but the bottom end has just gotten louder.I'm thinking perhaps we should just throw in some bearings for good measure, but std bearings are definitely not cheap, but of course, neither is a crankshaft if one goes. It does appear to have the original injectors as well, but it has no smoke or missing at all, runs as smooth as always. Listening to the injector pump is noisy, but it may just be how the Roosa's are, can't answer, should probably compare it to my 6.9. Opinions/ideas?