DAHAYES

I have a 99' Malibu that has a 3.1 V6 in it. My engine locked up on me the friday before last and what had happened was that i had spun a cap bearing on my crank soi bought a new crank with new bearings and put it all in and then i started my car....It ran fine but the very next day i started it up and i had a piston rod knocking so i jacked up the car and dropped the oil pan and got a look at the crank and everything was fine.....all the bearings are the right size.....so now i am stuck and idk what to do.....anyone have any answers for me?