[shredder70]

I have a cj7 with a rebuilt 390 amc v8. Runs like a raped ape.. Ok, Now on to the problem.. It has 50# oil pressure at start up, when it warms up it has 5.. If I rev it above 1250rpm the oil pressure comes back to 15-20 lbs.. I changed from 10w/30 to 20w/50 and it helped a little.. I ordered a oil pump kit and am going to try that tomorrow.. The engine was rebuilt approx. 20,000 miles ago and does not smoke and runs great.. I saw recipts from rebuild and am floored what it could be.. Any ideas? Thankx

 

[shredder70]

I just pulled the pan and the pan and screen are clean..
Pulling the oil pump apart now..

 

[Plato2k5]

is it an electrical gauge or mechanical gauge??

 

[shredder70]

Mechanical guage... Brand new..
I just pulled the oil pump apart and the front cover looks worn pretty good.. I think I found the culprit..

 

[shredder70]

Bump. Back again. Bought a oil pump wear plate and installed it still very low pressure..

 

[Smiley23]

Only thing left would be a slipped bearing (that I can think of) or plugged oil filter. What was the warranty on the rebuild?

 

[shawn]

Did you change your filter and oil? I had no pressure, and it was a plugged filter (I have a plugged filter bypass so a bad filiter = no pressure).

Otherwise, did you check your high pressure spring and plunger?

 

[scorpio_vette]

bad sending unit??? hook up a pressure tester to verify

 

[crassell]

mains are gone. after the oil warms up and thins out, there is too much clearance between the crank and main bearings to hold good oil pressure

 

[Cooter]

mains are gone. after the oil warms up and thins out, there is too much clearance between the crank and main bearings to hold good oil pressure

#1 most likely.

Plastigage it.

 

[Smiley23]

mains are gone. after the oil warms up and thins out, there is too much clearance between the crank and main bearings to hold good oil pressure

Especially since he tried a thicker oil and it made a difference.

 

[Strangler]

Where is your oil pressure guage hooked up to? I would just replace the transmission with a 2wd Muncie.

 

[FORD FLARESIDE]

#1 most likely.

Plastigage it.

x3:thumb:

 

[Spork]

if the spring in oil pump is worn out it will cause the same problem. I have a 360 that does the samething. Replace that spring before you start pulling the crank.

 

[Cooter]

Thge pan is already off, and he doesn't have to pull the crank to plastigage it.

I'm betting on worn mains.

 

[shredder70]

OK here it what i did so far..
New mechanical guage.
Dropped pan and checked screen
Rebuilt oil pump with new gears and spring and plunger
Rebuilt oil pump with new wear plate.
Changed out timing cover with a known good one off of a 304.
Drank lots of beer and scratched my head..


I have 5-10psi at idle and 40 at 2000 rpms.. Motor runs awesome lots of torque just bad oil pressure.. I guess I will just pull it and put in another bullet..

 

[Cooter]

Just run it if you aren't going to check anything else. 10lb/1,000 RpM is fine, and you get better than that at 2,000. I ran a MoPar 360 in my Scrambler for 3 years with barely any oil pressure at idle....

 

[shredder70]

Just run it if you aren't going to check anything else. 10lb/1,000 RpM is fine, and you get better than that at 2,000. I ran a MoPar 360 in my Scrambler for 3 years with barely any oil pressure at idle....

I would but it has fresh pistons cam and everything else.. Plus at idle I can hear a little man knocking on the side of the oil pan..:tonka:

 

[shredder70]

It just went so fast. Good oil pressure to no oil pressure..

 

[Cooter]

Plus at idle I can hear a little man knocking on the side of the oil pan..:tonka:

You have your answer right there. Bad bearings.