Low oil pressure?

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Cope

Fusing with fire
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My new engine is having an oil pressure issue.

At idle I make 25psi hot, 50PSI at 1000 rpm and 65+ above 2000 rpm.

I've been doing some freeway testing and after 15 min at around 2,500-2,000 RPM I got off the free way and oil pressure dropped to almost zero. We're not talking hard on the breaks or down hill just sitting at the light. I put my foot in it to bump it up back to 25 so it was not idling at zero. Twice now I've seen it do this.

HV pump running 20-50 Joe Gibbs oil.
Factory car pan.

Maybe 200 miles on a full build.
Balance, blueprint the whole nine yards.

I'm on my second oil change, I drained it at about 100 miles and cut the filter just to make sure all was well. No metal in the filter.

11.5-1 comp ratio.
Big lumpy cam (dont have the specs on hand)

Any ideas, I'd hate to pull the engine again but I also dont want to ruin my new engine...

Engine was built at a very good, high performance machine shop.
 
Oops. Doesn't sound good. The first thing I would do is install a (or a different) manual gauge to make sure the reading is correct. There are many places inside a Mopar small block where oil pressure can go. Manually test the pressure and report back.
 
I would guess your engine has very loose main and cambearings. Do you know the bearing-plays the engine was assembled with?
Are you running adjustable roller rockers perhaps too? That would also be 'good' for a psi drop.

25psi idling hot is already low in my book.
ESPECIALLY with superthick oil and a High Volume pump.
 
Stamped rockers for now.

I dont remember the clearance but it was checked. I'd have to dig out the paperwork.
 
Something as simple as leaving a galley plug out behind the timing cover could cause the problem. If the block was boiled and the galley plug under the rear main cap wasn't replaced could cause the issue.
 
What's the orientation of the shafts? I can never remember....
 
The oil holes need to point down and oriented to the valves.
On stock rockershafts there will also be a notch on one end of the shaft, which will face to the center of the engine.
 
So the notch faces the carb?

I dont remember a plug under the rear main when I tore it down..

****, more and more I'm thinking she gonna come back out.....
 
Standing at the fender of the car looking in at the engine the notch on the shaft will be to your left and down.
Either Fender left and down. It does not point to the carburetor.
So on the front driver side it's down and on the passenger side it's at the rear and down.
 
the plug under the rear main cap will not effect oil pressure it directs oil thru the filter
 
At the same time I also recommend that you replace the stock bolts with harder bolts. the old Originals will strip or break. Do not over torque them.
 
If that plug underneath the oil sending unit is not in there it most definitely will affect the oil pressure.
im not talking about that plug . I am talking about the one under the rear main as mentioned .
 
The strange thing is it only happens when I get off the freeway..

Around town is ok.
 
im not talking about that plug . I am talking about the one under the rear main as mentioned .


That is the plug under the rear main cap if you turn the motor over you'll see that's where you screw the sending unit in.

If that plug being out doesn't make any difference then why would Chrysler spend the time to put it in there.
You won't notice that plug just looking but if you stick a long bolt in there you can feel it. And if you drive it out you drive it out from the top using a long push rod.
 
Here!

Oil galley plug enlarged.jpg
 
it directs oil thru the filter . without this plug the oil will bypass the filter .
 
Oh boy....

I dont think I ever drove that one out....

That passage could have been full of glass beads.....
 
That plug is sitting approximately 7 and a quarter inch down inside that hole. You can check to see if it's in there by taking off the oil pressure sending unit and inserting a rod and measuring how far it goes down.



If it goes over 7 and 1/2 in then it is missing.
 
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