low oil pressure

I did search but didnt come up with anything

on my 89 4.0 renix motor I have about 50 miles on the rebuilt motor, cant get ahold of the motor builder untill after new years. did the "run it hard and down shift" break in method and am using 10w30. the builder did a .30 over, chamfered the holes, balanced the rotating assembly,line honed and shaved all surfaces to true we used the original cam/crank/rods but everything else is new. the motor was actually in really good shape prior to the rebuild, round cylinders still showing cross hatches, none of the bearing surfaces where mared or out of spec and the flat surfaces were damn near flat. I didnt know the motor was so nice inside, odometer read 195K and I assumed the worst. we ordered the kit prior to pull the motor so i could drive it till the last second and would be able to get oversized bearings locally if needed. I have used this builder to build all my racing 5.0 long blocks and his quality is top notch.

Now onto the question-
when engine is cold I have 40 psi at idle 50-60 above idle. Once it warms up I get about 15 psi at idle and 25-30 psi above that. During initial break in the pressure never dropped below 50-60 warm. This is reading a manual gauge with plastic line.

there isnt any dents in the pan and I dont know if he checked clearence for it( I can only asume he did, been doing this a while) Do I immediately assume rod/main/cam bearings, oil pump or is there a "Jeep" only thing I am overlooking?

any help/ideas/suggestions would be greatly appreciated.

Mahalo, Jeremy

this may sound dumb but did you use a fram filter? Using a poor quality filter can have negative effects on your oil pressure, maybe it's just that simple?

And after the initial breakin period you did an oil and filter change right ? EVERY rebuilt I have had I changed the oil and filter at 500, 1000, 1500.
X10 on the Fram, they only time I will use them is as throwaways for a flush where they are only going to be on there for less than an hour or two.

I agree with your concern after the coin you've put into this engine.

First thing I would do is to verify that this pressure is real by trying another one. I know you are using a mechanical gauge but if you only have tried one gauge, you really need to try another just in case Murphy is lurking. Don't want to be chasing your tail. If your readings with the second one are the same, then of course you know what you've got.

15 psi is low at idle but within Jeep spec of 13 psi at hot idle. However your higher rpm oil pressure is out of spec as Jeep spec is 37-75 psi ABOVE 1600 rpm and you are at 25-30.

I know you can't get a hold of the builder right now but if you don't stumble onto this, you certainly have a valid concern to talk to the builder about. What kind of warranty do you have on this work? You mentioned he's a top notch builder so hopefully he'll stand behind this and you can remedy it.

whats wrong with Fram?

VTEK1 said:

whats wrong with Fram?

Click to expand...

!!!1 Oh noes....here comes 8 million pages.

VTEK1 said:

whats wrong with Fram?

Click to expand...

Let's just say that people have some pretty strong opinions when it comes to oil filters! And Fram is not beloved by all.

I believe I did use a fram cause thats all I could get on island at the time
Im doing a filter change tomorrow, I still have under 60 miles and am not driving it anymore till I get the pressure up.
My builder has become a good buddy of mine and I work with him often in his shop, I just am trying to get the jeep shipped before new years and am hoping this doesnt need his attention. He will stand behind his work 100% no matter whos motor, its a small island so people USSUALLY try hard cause once the word gets around they finished.

I ordered a wix filter so I will do the change once it comes in. Ill let you guys know what happens.
Thanks guys, Jeremy

Frams have been known to fail internally and cause a fatal loss of oil pressure. In this case, it sounds like normal oil pressure for a factory spec engine. The FSM states this range of pressure hot. Mine runs that until I dropped in teflon additives. It runs that low again lately.

Oil pressure is directly related to bearing clearances. I don't see much to tell us what was exactly done there - machined oversized, how much, what brand bearings, new pump, etc. Moot point, the oil pressure range is running to the book, IMHO. Sorry.

10-30 is my problem now, so I'm moving to 15-40 to get the increased zinc phosphate additive for a flat tappet motor.

My '90 has 185k on it, so it will get a periodic compression test now to monitor what's up as I continue to drive it.

as far as teh bearings surfaces all he did was polish the surfaces, check clearence and it was tight with new bearings. I know he smoothed out some of the oil journals, this is the first 4.0 motor so maybe he got a little over zealous with it. I allready have a new 4.2 crank, rods and pistons all cleaned up, balanced and ready for install. didnt want to do it till next year but I can use them if I absolutley need to right away.

I'll give an update when I do an oil change, maybe it could be that simple.

TiRod said:

Frams have been known to fail internally and cause a fatal loss of oil pressure. In this case, it sounds like normal oil pressure for a factory spec engine. The FSM states this range of pressure hot. Mine runs that until I dropped in teflon additives. It runs that low again lately.

Oil pressure is directly related to bearing clearances. I don't see much to tell us what was exactly done there - machined oversized, how much, what brand bearings, new pump, etc. Moot point, the oil pressure range is running to the book, IMHO. Sorry.

10-30 is my problem now, so I'm moving to 15-40 to get the increased zinc phosphate additive for a flat tappet motor.

My '90 has 185k on it, so it will get a periodic compression test now to monitor what's up as I continue to drive it.

Click to expand...

Teflon, man even dupont who OWNS teflon says it's not for use in engines yet snake oil companies continue to use it in the their products.
http://www2.dupont.com/Consumer_Lubricants/en_US/products/dryfilm.html
See any engine oils in there ? Think they would not sell it if it worked.



More
http://www.quickhonda.net/teflon.htm

I was messing around under the hood a minute a go and noticed I have a napa gold filter. I dont beleive it is the filter giving me problems anyway, I would expect it to be on the low side during warm up. Im going to try a different gauge tomorrow and a oil change comes in a couple days. If that doesnt work I get a stroker out of it

Teflon is a good oil pressure builder because it blocks up the passages without major friction increases.

Polishing the journals and relieving the grooves opened up the clearance, even with new bearings. "Checked and it was tight" isn't in the FSM, it's supposed to be measured in .0005" increments and to spec.

What was the reading when the clearance was checked?

Again, 10-15 pounds hot is what the book says is ok. Chevys run lower. A warmed up engine with hot oil doesn't have as much frictional resistance, so it doesn't need excessive pressure. That's an old race car myth from the days when it was a cheap cure for a lack of high rpm parts. Not something a Jeep does.