How long have you had this engine? What is the stroke, bore and deck height, fuel system and fuel, and any other info you have. I had a 463 with a olds rocket block, dry sump, injected on alcohol and also had main bearing problems. Mine was a 4.250 stroke with a 6.030 aluminum rod. top side of rod bearings would be a little hammered but never into the copper. Tell me what you can and we will go from there! Thanks,Don