Oil pressure issue

[farmtruc]

Hey guys, hoping you can help.

I just built a forged 6.0L for an '05 GTO. BTW, this gto layed down 630+ with 10psi, procharged, l92 heads, small cam. Now it has an upgraded D1sc charger, 14psi, better cam, I can't wait to see it run.

Anyway back to the issue.

The engine has low oil pressure. Here's the situation. When the engine is first started up, it has about 38-40psi, ok kind of normal, but slightly low. When I rev the engine to 4-5K rpms when it's semi cold, I can get 60psi out of it, still kind of low.
BUT, when the engine is hot after about 20mins of driving, the engine oil pressure is 5-9psi at idle and no more than 30psi at wot. Very LOW!

Here's what I've checked:

-Made sure the rear plastic plug behind of the rear cover was there, it is and the oring is sealing.
-Made sure the front steel plug behind the timing cover was there.
-Replaced the oil pump
-When we assembled it, we were very careful about cleaning every component and pick up tube.
-The oil pump o ring was there, but replaced it when the new pump went in.
-Changed the oil and filter
-Installed an external mechanical gauge to ensure the pcm and sensor was correct, it's still hooked up

Tomorrow I'll double check the cam retaining plate just to make sure the seal is good behind that, but I'm sure it was when I put it on.

New lifters
New pump
New bearings
New valve job
New Everything!

Any other ideas you guys might have?

thanks,
allen

[RedHeartbeat]

Gotta get the oil pump centered up on the crank or it can wipe it out. Also, did you pack if full of grease or something to keep from dry running the pump at startup? Another thing to check in the pump pickup screen to botton of pan clearance, should be about 1/4". Stroker kit engines have issues with this from time to time. Too close and the pump cavitates, sucks air.

[RedHeartbeat]

The last 408 that I had oil issues with had bad main caps, pounded out of round. I unbolted the caps and they fell out of the block. It was as you describe, good OP at startup but nothing once the engine warmed up.

[Defunct SO]

excessive bearing clearance?
sucks when stuff like this happens.

[NITROUS]

I have to agree with trtturbo. What kind of bearing clearance do you have?

[SCIV]

Mine was the oring being bad.

[RedHeartbeat]

A bad or wrong size oring will definitely make it suck air once the oil warms up.

[SCIV]

I think i had to get a bigger (thicker) o ring if I remember correctly.

[RedHeartbeat]

There are about 4 different ones you can get, red, blue, green or brown. I'm thinking the blue was the thickest one for the 6.0L truck engine. I'm probably wrong though.

[GMCwantsLS1]

The last ones I got were the red one for the truck setup and a blue one for the f-body setup.