Need the history on the engine you bought, but I will say zero oil pressure is very rare and indicates a major problem. Front cover needs to come off. You could look at photos of front covers off online to understand the flow. The flow is basically pump - cooler - filter - engine. If you pull one of the plugs and pressure fill it you will prelube the engine. Go the other direction and you will prime the pump, you could actually gravity fill it. Look online there is a lot of information on air over oil priming systems used on LS series GM engines. If you do that you can actually determine likely oil pressure when running or conversely if you have a major issue ie walked cam bearing or other issue.

Agree with others, once the pan is off, check the rod bearings just for good measure, will give you a good idea how much wear on the engine.

 

 

 

 

I'd pull the front cover and inspect that oil pump for sure.

 

So that "rubber" piece. I'm thinking excessive RTV squeezing out inside the pan maybe?
Looks like you found a blood clot in your trucks arteries, hopefully you caught it in time.

 

Hopefully there isn't any more stuck in some inaccessible place.. my guess is a pump/cover issue. If not, to be sure, you may have to disassemble engine and make sure all oil passages are 100% clear. Good luck.

 

There was almost no RTV on the oil pan gasket, there was a nice thick rubber gasket with metal grommets that was in great shape. I guess it could have come from somewhere else above. Aside from the mysterious rubber piece the pan was in good shape, no thick sludge, no metal pieces etc... I did not see the post about checking rods and cam bearings until after I had everything bolted back up. I am not sure i would have known what to look for anyway on that one.

I keep telling myself that because the engine probably set out for a while oil cooler lines open that the engine just lost its prime and that is all, I am an optimist.

Friday night football this evening, so front cover will have to wait until morning to come off.

Thanks to everyone for their continued help regarding this.

 

Since you have to pull the oil pan again, to remove oil pump cover...as mentioned earlier...check the o-ring on the pick up tube. Also, as bad as that looks, rubber piece in pick up tube...there was still plenty of area surrounding rubber piece to draw oil up the tube...if o-ring was good and oil pump is functioning. Yes, not perfect scenario...but it should have made oil pressure.

If o-ring is good...then front cover must be removed.

​​​​​​​ Brian.

 

Progress. Because you've proven fouling, you will want to remove each piece and verify that you can physically pour oil through all passages, oil pickup tube, oil passages in front cover, etc.

With the oil pan off, you will want to unbolt the lower halves of all 8 pushrods such that you can remove all 16 rod bearing halves with your fingers (easy). You can inspect them for bronzing to give yourself a ballpark idea about the wear of the motor, but never reinstall them. Always reinstall fresh rod bearings.

New rod bearings will always improve any oil flow. Same for new main bearings if you are feeling spunky. I mean, the oil pan is off and they are just sitting there waiting to be replaced...


Anyway, next you'll want to shine a bright light UP such that you can see if any cam bearings have walked. Walked cam bearings crush oil pressure and are best changed with the motor out, though there is some wiggle room here.

If the cam bearings haven't walked then you will want to remove the front cover. Pour oil through the oil passages to verify no hidden clogs. You also want to note if the front cover has any gashes from extreme wear (also bad for oil pressure).

At this point you will be looking at your oil pump gears which are most likely broken/cracked but still inside their races/cage area. Cheap and necessary to replace (lightly, never fully, packed with vaseline). Peace of mind if you replace the oil pump / cam timing chain with new, as well, though it is typically a trivial player in oil pressure.



THEN...you can button her all back up, refill with oil, and retry.