Brak Attack

iTrader: (10)

I had just completed a head and cam swap on my car. I put in a ported LS6 oil pump and I am absolutely positive I did not pinch the O-ring. When I first started the car I was getting a steady 45PSI right off the bat for 15 minutes straight until I had to shut the car down (overheated). The 4th time I started the car the oil pressure was normal for the first 2 minutes (40PSI) and then it dropped to 20PSI. Shortly afterward I had 0 and I gave the throttle a quick blip and it jump back up to 40 and it stayed there. Now everytime I start the car up I have poor oil pressure for the first 2 minutes and it eventually settles out at 40PSI. I am skeptical of the replacement O-ring I used as it is not the GM factory one but the one I used was identical in size and fit snug on the pickup tube. Anyone on here ever had the sam thing with their car?