Lifters

[Batman]

If you go into the oil pump to do the O-ring get a ported pump and an LS2 timing chain while you are in there, money in the bank for the future. But if your oil pressure isn't dropping I'll tell you now it isn't the pump or O-ring. Navy's issue was different as his Oil pressure was getting down between 15 and 20 PSI at idle. If you are sitting at 35-40 PSI at idle the oil pump is fine. You can't have a lifter knocking from starvation if the car has good oil pressure.