Thoughts on 455 oil pressure drop?

Ok, so far it sounds like your dodging a bullet, no major junk in the oil, no noises from the engine.
Go forward with testing EASY.
What I would do is watch your tachometer (RPM) if your only generating 20/25 psi, spin the engine NO FASTER than 1800 rpm.
If you can generate 25 psi max only, it sounds like something is causing/opening/bleeding off any extra pressure.
The only thing I can think of are the two staked in oil galley plugs, you have to remove the timing cover to check these.

 

Cover is off. What area are the galley plugs location?

 

Behind the cam gear

 

You can see the one on the driver's side.

The other is same place on passenger side, just rotate the crank to get the window aligned.

 

Both appear intact. Looks like I’m pulling the engine in the near future.

 

Is 10w-40 a bit light?

 

I don’t think that’s the issue. Wish it was that easy though.

 

Could the pickup tube gasket leaking cause a low oil pressure situation?

 

That’s a possibility...going have to do some digging when I get the engine out. I installed the pickup with gasket, torqued the bolts and blue lock tited them to boot. I’d be happy if that was the only issue.

 

Btw I appreciate the help and input so far from all forum users!

 

Yeah "tight" tolerances for Chevy is out to tolerance for a Buick.

 

At least your filter looks clean, did you pull the oil pump apart to check things out? I can’t understand why it would lose pressure with throttle.

 

The oil pump is a TA blueprinted unit, I don't think it is the problem as pressure is 70-80 on start up. Just started the process on pulling the engine this last week. I'm removing the radiator and grill so I can pull the engine and trans as one unit.
I hope the issue is just main bearings need swapped . Also I want to install a new rear seal as it appears to have a minor leak.

 

The valve you guys are talking about a page back is the oil filter bypass, not the pressure relief valve. That valve is in the bore behind the big nut (or pressure regulator). Remove the nut or regulator (standard right hand thread) and then use a magnet to pull the relief valve out..

Lack of increase like your describing is often a stuck pressure regulator valve.

The valve is a very close tolerance to the bore, and it does not take much to stick it in the bore, partially open.

JW

 

as i found running big oil pressure, is the dist/cam gear wear due to the up/down rpm and high o/p. its somewhat an easy fix on the 350, both gears are separate, the 455 cam gear is the cam. not nice.
also due to age and up/down rpm/oil pressure, the t/c hole for the dist will stretch. found that last time i did the 350.

 

Removed the pressure regulator it appears clean and came out mostly without resistance with a magnet. I did notice that when push it back and forth it does seem to catch slightly as I rotate it. Not sure if this because it’s cocked slightly?

 

Well think I found the problem
Pulled the oil pan and there was (gasp): a paper towel hanging off - covering the pick up screen. Highly embarrassing as I was the one who installed the pan. Only thing I can figure is I dropped it in there while I had the pan partially off in the car while hammering the side of the oil pan out to keep the crank weight from knocking the oil pan last year.

Plan is to pull the oil pick up off and spray it out to make sure nothing major got past the screen.
Any other recommendations while I have the motor out?

 

Check the condition of main and rod bearings.

 

Okay, think I should Plasiguage the mains as well? Also if it all looks good do I need to pack the oil pump with petroleum jelly again before fire up?