hemijim

was trying to help a friend out, he has a very nice class47, when he first got it, there was a knock in the motor, after pulling the o/pan off, he noticed the #3 con rod was loose, the babbitt was chewed up, the crank didnt have any deep scores, he had another rod, so he replaced the bad one, everything was great until today, after a short trip for an inspection, the knock came back, same rod #3, any clue as to what may be the problem here? or advice on what to look for, etc... his daughter is getting married next week, and planned on going in this car, any help greatly appreciated.....