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1995 Sub oil pressure

5256 Views 11 Replies 5 Participants Last post by  R3dn3ck
Okay, my Dad has been concerned lately about the oil pressure in his '95 K2500 7.4 Sub.
When you first fire it up, you get between 70-80 psi (which I would expect), but when it gets to operating temperature (200-210), the oil pressure drops down to about 20 psi.

The previous owner had this same issue, and prior to selling the truck to my Dad, had a high volume pump installed. Pressure is the same as it was prior to the pump.

About a month and a half ago, we were heading to LA, and when we got into the hills (Acton), Dad decided to put his foot in it and see what the boat anchor 7.4 could do. At RPM (4500 or so), it built enough pressure to blow out the rear main...No, we have not replaced the rear main yet, but we did use a bottle of bars stop leak, and to my surprise, it seems to have worked...

Now, 20 psi hot doesn't concern me, but it definitely concerns my Dad. This engine has almost 200K. I recently changed the oil, and smelled no fuel in it, so I know it isn't the rings. This truck does not smoke, even on start up, so I know it isn't guides, and there is absolutely no valve train noise, or lower end knock.

Does anybody think he needs to be concerned with the 20 psi? If so, any suggestions on remedies?

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Is this 20 psi at idle Jess? Does it go up with the RPMs? 20 PSI at idle is acceptable. Many in the GM fraternity (Zora Duntov, Smokey Yunick, Warren Johnson) say all you need is 10 PSI per 1,000 RPMs.
Yeah, it fluctuates between 20 and 40 psi depending on rpm.
i always heard " only worry when you NO oil pressure and not about low pressure" but if it increases with rpm you should be ok
Yeah, that's how I feel, but Dad has been worried for some time now. I told him that if it gets worse, we will just dump in a quart of 90 weight! lol
He might be looking for an excuse to rebuild or slip in that big 502 crate the GM has.
What rpm does it take to get the 40 psi with the engine & the oil hot Jess?

X2 on the BB Crate Engine !! Can I have his old one? :)
If the pressure actually IS 20, then I wouldn't be worried. But pressure verification with a known accurate mechanical gauge is in order first and foremost.
Generally at about 2K the oil pressure hits 40 or so.
any leaks? cuz that may do it unless yall fixed by now
Just puttering around the hills he does around here, everything seems to have sealed up, but he hasn't really put his foot in it to see what it does...
all i can say then is lay it down and see but you may run the risk that it could mass up again so really its 50/50 so im no help to yeah haha
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