excessive oil pressure

[madkaw]

DJ,

Thanks for all the good info. I've been down this exercise before and have traded out springs, pumps. Right now I am running stock pump and springs- but will verify. I've basically ignored the issue because it wasn't a low psi problem. Now I have my head off I want to make sure my high PSI isn't from a blockage.

Not too many folks have had this issue , so not much to compare too.

[djwarner]

Re-reading what I posted, I'd try to remove the washers in the nut cap first. They are actually called shims in the parts manual which usually indicates they are meant to adjust something. Since they are part of the bill of materials, all three should be in there even if they are not needed. Too many shims will raise the pressure.

[Captain Obvious]

How about pulling the valve cover off and seeing what kind of oil flow you've got up at the cam while you're spinning the pump? Might give you some insight into whether the pressure is high throughout the system as opposed to something restricting the flow closer to the pump?

I'm thinking that if you get great flow out of the cam, then you've got an overactive oil pump. But if you've got 75psi at the pump and just a dribble at the cam, then you might have a problem somewhere in between?

Just tossing out ideas...

[madkaw]

Lots of pressure up top and a pretty shiny cam to prove it.

Like I said, I have been battling this for a long time. I've been told that the pressure is NOT too high, but no one else runs a constant 70psi on a street motor. I have also been told that the high oil pressure wouldn't cause the crank seal leaks, but I have leaks both ends.

I didn't trust my Datsun gauge and mounted a mechanical one to be sure. I did this latest experiment to verify gauge accuracy and to eliminate any pressure contributions from a running motor.

I might just be done with this L24 block if I don't find something definitive. I have a L28 short block sitting on a stand that just needs some cleaning I believe.

[Zed Head]

I think that this was mentioned on Hybridz but oil pressure is really a measurement of resistance to flow. The whole lubrication is designed such that the ~40-60 psi average reading is an indication of proper flow. It's a secondary indicator and can be misleading. It doesn't guarantee flow, it assumes it. Ideally, we'd have flowmeters in the dash showing that oil was actually going where it should.

If you have a stock pump, correctly adjusted, and you get high pressure all the time, then that might mean there's a restriction of flow somewhere. For example, if you installed your crank bearings backwards (I think it's possible for a few) the oil flow passage would be blocked, and pressure would increase. Or if your port to the head was blocked, the same thing.

And the rear seal is open to the crankcase. So really shouldn't be affected by oil pressure.

[madkaw]

You did help out a bunch Zed. I believe I have a blockage deep in the block somewhere. I know I have been careless before because I found a piece of foil in the bottom of my oil pan before. It was one of the sealing foils-possibly from an additive bottle. It was all balled up and beat up like it had been beaten around my engine. So maybe something else is partial obstructing a passage way?

Unfortunately, there will be only one way to find it. I will try removing the end plugs and cleaning out the main galley first. I will run pressurized air thru there and hope something lets loose. The problem is that I won't be sure I did anything unless I find something. It might be a total tear down. Maybe I will find a bearing misplaced, but I don't remember having this issue from day one.

One thing about fresher motors-they come apart without much fuss.

[Captain Obvious]

Well it really sucks to tear down the motor not knowing what it is your looking for, or even if there's anything at all. Could you feel comfortable with one assumption... The assumption that if there IS some obstruction somewhere, it is upstream of the pump. Between the pump and the filter?

If you operate under that assumption, then maybe you could just drop the pump and remove the filter and blackflow from the filter holes back towards the pump and see if anything pops out? Make some sort of block off plate that you could bolt onto the filter location to facilitate an air or solvent supply?

[madkaw]

I am going to make every effort to NOT tear it down and try what you are describing. Also remove rear galley plug to facilitate cleaning.

[Captain Obvious]

I've never studied the intricacies of the oiling system routing in the block, but that rear galley plug is post filter, isn't it?

Also, someone mentioned the possibility of having the crank bearings in backwards thereby blocking off the oil holes. I'm assuming that crank bearing(s) with no lube would have spun long ago, right? There's no chance that this is the issue is it? Hey... I have to ask.

[madkaw]

This is all learning for me Captain. I imagine the back plug is a clean out point.

The 'How To Modify' books shows the oil schematic.

As far as the bearings- in my case it might just be a partial covering of a oil hole that would do it.

[Zed Head]

I mentioned the backward bearings just to illustrate a possibility. Pages 116-117 of Monroe's How to Rebuild book talks about the various ways to get them installed wrong. Matching holes, block versus cap, aligning grooves, etc.

Sounds like one of those really difficult problems to solve. If you have an extra assembled short block, you could compare flow rates through the passages by filling with a funnel and watching the drain rate, while blocking passages. Or something similar, I'm not even sure where you would start.

Even though you don't have signs of a spun bearing you might look for signs of heat buildup from lack of oil. Discoloration.

Edited September 1, 2014 by Zed Head

[Diseazd]

If you put your cap bearings on the block side, you'd have known it within minutes of fire up. That's not the problem. IMO

Edited September 1, 2014 by Diseazd