401 oil pressure drop

[acofficer]

I have read all the posts but haven't found one with the exact same symptoms as me. I would love some input from the experts here on the board.

The history of the engine is somewhat unknown. I bought a 1976 J10 from a guy. He said it had been rebuilt with a mild cam. I ran a compression test on it and got 120 psi on all cylinders here at about 6000 ft above sea level.

I just finished swapping it into my Jeep. It is running a little warm.... about 210 under load. I am going to flush it with BG cleaner.

My big problem is that at startup I get about 30 psi oil pressure. As the engine warms the oil pressure drops to about 0-5 psi. I am going to pull the filter and get a napa gold. I will check the bypass valve then also and try to check my clearances. Does this sound like a oil pump issue or a cam bearing issue?

Also, if my clearances are bad, I may try and grab a timing chain cover off a cpl of 86 and 87 360's my friend has in his garage. Will these covers interchange?

Any thoughts on what you think is going on and what I should check. Thanks!!

[jeepsr4ever]

I would start with the cheapest. New set of gears and a midplate to cover the damage on the top of the oil filter adaptor/bottom of the pump. Sounds like the T cover is out of tolerance.

[tufcj]

Like MC says, cheapest and easiest first. I've seen that the spring on the pressure relief valve weakens with age.

A new pump gear set usually comes with a new plunger and spring, and a mid-plate from here at Bulltear. Make sure the relief plunger is installed point forward. If that doesn't solve the problem, then replace the timing cover. Yes, all V-8 covers interchange.

Look at your oil filter adapter. Older ones have a 90* bend going into the filter, newer are 45*, the newer ones flow better. A 76 should have the 45*, but it could have been changed.

Bob
tufcj

[acofficer]

Ok, I ordered the HP pump kit and the midplate. I will try that first. If no luck I will then change the timing cover. I am praying it is not cam bearings.

[acofficer]

I have not had a chance to check the tolerance between the side of the gear and the timing cover yet, but I am wondering if anyone has ever tried a speedy sleeve inserted into it. Here is a link to the chart of sleeves:
http://www.skf.com/files/344136.pdf

What are the dimensions supposed to be?

[acofficer]

oops, didn't realize till I got in there that the cavity is not round. Sleeve won't work.

[acofficer]

Just FYI new gear set and midplate did nothing. I changed to a mechanical gauge though and the actual readings are 18 psi at hot idle and bumps up to about 40 psi as rpms go up. I think I am going to leave it as is now.

[dagazio]

I am looking at a simular situation. However, I believe my 401 is not rebuilt and has 95000 miles on it. I have a 1974 Cherokee and it looks like the motor was never pulled. However, the rear main seal had let loose and when I pulled the bearing cap to replace it, the bearing was pretty well worn. The gauge on the dash, it starts out around 40 psi and drops near zero when hot and idling. I'm using 10w-40.

I'm not interested in rebuilding the motor at this time. I would like to get a few more mile out of it before I go though the trouble. What worries me is from experience, zero oil pressure spins bearings.

[acofficer]

I just ordered a new timing cover. Hopefully that will bring my oil pressure back up.

[tarior]

I strongly doubt a new timing cover will do it. You'll likely need to tear it down and put some cam, main and rod bearings in it. That's been my experience.