Oil Pressure and Engine Options?

[GirsMJ86]

OK, I brought this up somewhat in skimore11's "What engine?" post and I thought that rather then steal his post for this I would start a new one.

 

Eagle brought up that these engines run around 55-60psi at 55mph close to new and like 45-50psi at 55mph when at like 200k miles and up.

 

My 91 has a pretty much new engine in it, only like 4 years old. Jasper remaned 4.0L HO with almost 16k miles on it. It sat for awhile before I bought it off Rob and he hardly started it. In fact they had to jump it to get it onto the trailer when I got it. So it does burn some oil now, you can really only see it when it is left to idle. So I am sure some if not all seals are shot. It only leaks maybe a drop on the ground, not sure from where but seems like headers or something. Oh, and it is running pure synthetic SynPower oil and I even put a quart of Marvel Mystery Oil to get it to try and recondition the seals a bit, didn't work.

 

I was driving it today and the oil pressure at 55mph with like 1700 RPMs was only 20, yes you heard that right, 20psi. Now when I gun it the psi jumps to like 60 or more, have not had it max out though or go into red. Most the time it is around 20 though.

 

Jaspers warranty ran out at 3yrs or 100k miles so I can't just get it redone for free. So, options? I have no clue what would have to be done or anything, most I have done with an engine is put a new remaned on in my K-10. About how long does it take and cost? Maybe just order a new one from Jasper? Maybe order a 360 or 401 or something from em? Maybe something from some newer car that would fit; eclipse, camaro, talon... Thinking about something nice and fast since it is an Eliminator, but an easy swap. Could I put a last year 4.0L in it? I don't know, ideas please.

 

Alex

[LEAD_NOT_FOLLOW]

How are you verifying your PSI?

 

The 4.0L is known to have faulty sending units to the gauge. To check the gauge turn ignition on (do not start) and needle should go to zero. Unplug at oil pressure sending unit and gauge should go off scale to the right if the gauge is working. Most likely it is the sending unit.

 

However your numbers do not sound bad. If you "punch" it and it goes up thats normal.

[ejndssn]

drop the r/t 5.9 into from a GC or Dakota if you want performance or the GMC 4.3l 24v cyclone :brows:

[comanchedude]

First Like Alex alluded to, you need to test the oil pressure with another sender or you can temporally install a mechanical gauge to test for comparison as you may have a compromised reading

Also if you get 10psi per thousand rpm your ok

If your engine was starving for oil you would hear the rockers and lifters clacking.

Its common for people to get all hung up on oil pressure and think it needs to be a high number but the facts are you just need to meet the 10psi per 1k of rpm and your golden.

 

As for the blanked statement "like 45-50psi at 55mph when at like 200k miles and up"

 

That is not what I have seen and you would see on the 90% and I have owned a few dozen Jeeps over the year’s .if you had a 200k oil pump it would be ready for replacement and prolly just meet the 10psi per 1k rule. most "6cyl" engines I have had run 25-40psi at temp depending of course on rpm

and I think if you took a poll those are the numbers you would see.

[Eagle]

The first step is to hook up a good, verified accurate, mechanical oil pressure gauge and check the oil pressure at 1500 and 2000 RPM. This can be done in the shop -- the engine doesn't care if your actually driving or not -- oil pressure is a function of RPM. Period.

 

Assuming that your 20 psi is an accurate reading, then you need either new bearings, or a new oil pump. Rings don't affect oil pressure so it doesn't matter if the engine smokes or not. Seals don't materially affect oil pressure, either, because the pressurized part of the system isn't pushing oil at the seals. What matters is the clearance at the rod bearings and the main bearings.

 

This can be checked with the engine in the vehicle, using plastigage. It is necessary to drop the pan. It is also necessary to drop the pan to replace the bearings or the oil pump.

 

I think you need bearings. The fact you can get higher pressure if you rev up the engine tells us that the oil pump is capable of producing pressure. The most likely problem is excessive clearance at the bearings.

[LEAD_NOT_FOLLOW]

As I stated above, I don't think it's off by much.

 

Specifications

 

At Idle Speed (600 rpm): 89.6 kPa (13 psi)

At 1600 rpm & Higher: 255 - 517 kPa (37 - 75 psi)

Oil Pressure Relief: 517 kPa (75 psi)

 

The difference you see is probably due to a faulty sender and the "very inaccurate" gauge in the cluster.

 

My opinion is that Eagle is reading more into the problem than is needed. Just my opinion however....

[GirsMJ86]

Thanks for the input so far. I am going to get a friend of mine that has a shop and works on stuff when i don't feel like it to pull it in and check stuff for me when he gets the time. I wouldn't really think there would be anything major wrong since its only got 16k miles, but I don't seem to have good luck when it comes to cars.

 

I will post up what he finds out once he gets it in.

 

A GM Cyclone engine eh? hm... *wheels turning is not always good in my mind... lol* I was always thinking back when I had my 86 to stick a dakota magnum in it in place of the 2.8, wonder how hard that would be. those magnum engines are fun.

 

Alex

[GirsMJ86]

One more thing I forgot to bring up. When I press in the gas pedal and hold it there to maintain speed, at any speed, there is a loud squeal/whistle high pitch sound going on. It stops if I press the pedal in a tad more or release the pedal. But of course it comes back once I find a spot and hold it there again.

 

So, my question is what is that sound cuz it is starting to drive me nuts. Something to do with vacuum maybe? I don't always feel like having the music up to cover it and my other mystery noises up. :brows:

 

Alex

[Eagle]

My opinion is that Eagle is reading more into the problem than is needed. Just my opinion however....

Not really.

 

I am well aware of the factory oil pressure specs, I've quoted them to a lot of people. But 1700 RPM is more than 1600 RPM, and 20 psi is barely more than half of 37 -- and 37 is the minimum acceptable oil pressure at 1600 RPM.

 

Will engines run on less? Sure. I once drove a car hauler from Connecticut to Maryland and back that generated all of 10 psi on the highway. Wasn't my truck and the owner said not to worry about it, so I didn't. But it wasn't "right." In the present instance, we have a fairly low-mileage rebuilt engine. The oil pressure should be within specifications. Will it run on 20 psi? Obviously -- it is running. Is it right? No, it isn't.

 

It's not up to me to decide whether or not the owner should worry about it. He IS worried about it or he wouldn't be asking questions. I'm trying to help diagnose the problem. And when the oil pressure is half the minimum specified by the factory --- IMHO that's a problem.

[Pete M]

One more thing I forgot to bring up. When I press in the gas pedal and hold it there to maintain speed, at any speed, there is a loud squeal/whistle high pitch sound going on. It stops if I press the pedal in a tad more or release the pedal. But of course it comes back once I find a spot and hold it there again.

 

So, my question is what is that sound cuz it is starting to drive me nuts. Something to do with vacuum maybe? I don't always feel like having the music up to cover it and my other mystery noises up. :brows:

 

Alex

 

I think I can answer that one. :D What kind of air intake do you have?

[feerocknok]

So, my question is what is that sound cuz it is starting to drive me nuts. Something to do with vacuum maybe? I don't always feel like having the music up to cover it and my other mystery noises up. :brows:

Turbo.

[GirsMJ86]

 

There is my intake. Going to be making a cowl hood and making a cold air intake that will go along with that over this winter.

 

A turbo would be sweet. But it doesn't have one... yet. :cheers:

 

Alex

[Pete M]

My guess is the whistling sound is coming from the throttle body plate and your intake system isn't muffling it as well as the stock unit. Mine does the same thing. Annoying as all get out. :mad: