I put my motor in a couple weeks ago its an 03 sierra with a 5.3. Just bored it to 3.905 and used forged rods and pistons. My main clearances were .0015 to .002 as were my rod clearances. On first startup at idle I had 30psi and 60 at 2krpm. Well last night I got home from work and had only 10 at idle and 20 at 2k so I threw a new sender in and got about 15 and 30. I'm gonna put my manual gauge on tonight and see what it reads. I just spent 3500 dollars building this motor and now low oil pressure. I used a new gm oil pump. Any ideas.

 

What rods and bearings did you use? How did the cam fit? Use assembly lube or oil when putting the engine together?

 

Had similar issues with my forged 6.0, turned out to be bad bearing clearances. Didn't turn out well

 

All my new engines had 45-50 lbs at startup and would easily peg the gauge while reving the engine.

 

I was wondering about this too. When it gets up to operating temps, it would stay around 25-30 at idle. im sure its fine but wanted to hear it from others lol. Im just checking as its a new motor.

 

Used assembly lube clevite p bearings eagle h beam rods. Had between .015 and .020 clearances throughout rods and mains cam fit normally not extra tight or loose

 

With manual gauge warm I have like 12 at idle 30 at 2k and 40 at 3500

 

How soon did you beat on the engine after it was installed.

 

A couple hundred

 

pick up tube o-ring?