[footjoy]

I have a 389 bored to 400.It has approximately 500 miles on it. I bought the car with this motor in it so I don't know much about it. Mostly stock.

It always had 60psi oil pressure at 2500 rpm 40psi at hot idle 1000 rpm.

Last week we finally got the tri power dialed in and the choke and idle set now it idles hot at 850 rpm and it has dropped to 20 psi. Going down the road the gauge is a little jumpy. 40-60 psi.

Could this be a gauge problem or a pump problem?

Thanks
Greg

[67gtospud]

You can get another known working gauge to test whether your gauge is the problem or not. Otherwise there may be a small piece of dirt stuck in your pump pressure release.

[hurryinhoosier62]

20 lbs at idle is fine, but I have to agree that you need to get another gauge. The fact that the gauge neddle is jumping could be an indication that the gauge is going bad.

[Johnny406]

I had a similar problem a few years ago, there was a piece of Permatex about the size of a peeled thumbnail stuck in the pressure release.

[footjoy]

Originally Posted by Johnny406

I had a similar problem a few years ago, there was a piece of Permatex about the size of a peeled thumbnail stuck in the pressure release.

Is pressure release in the oil pump or the oil filter adapter?

Anyone ever removed the oil pan off of a 64 gto without removing the engine?

Thanks

Greg

[Will]

Pressure relief is in the pump.

I've never owned a '64 GTO so can't help with that question.

Definitely check with a known good gauge. I was driving down the freeway one night when pressure dropped to almost zero on the gauge. I freaked out, pulled over and turned the engine off. Got it towed to a shop where they hooked up a mechanical gauge and everything was fine. The sending unit had gone bad.

If you suspect the possibility of any internal damage, cut the oil filter open and look for metal in the filter media.

[b-man]

Originally Posted by footjoy

Is pressure release in the oil pump or the oil filter adapter?

Anyone ever removed the oil pan off of a 64 gto without removing the engine?

Thanks

Greg

To do that you'll have to unbolt just about everything needed to remove the engine, then hoist the engine about halfway out of the engine compartment just to be able to get the pan off. Then scrape gaskets, clean everything and try to get the pan to seal while laying on your back with oil dripping out of the engine.

You're much better off removing the engine and doing it on the stand.

Check your oil pressure with a good known gauge before you jump into pan/engine removal.

[70pontiaction]

But only ONCE..... and never, ever again!

First verify that a pressure problem exists with a known good gauge. AND cut the oil filter open and look for metal.

Like B-Man said, it's better to just lift the engine out and do it on a stand. You're not so messy, not so irritated, don't kink your neck so badly, etc., etc.

Besides, you need to check at least a couple rod bearings while you've got the pan off. And if you don't find any junk in the pump bypass, the engine has to come out anyway!

In reality, it doesn't take much more time - if any.

AND you can do a quick clean-off and shoot a nice, new coat of Pontiac blue on your engine. Pretty pretty again!

[steve25]

Possibly Two seperate things going on here guys, the idle rpm reduction to 850 when hot could be fully responceable for the 20 psi now seen at idle , the unsteady pressure reading could just fully be the connection on the sender if it's electric , or the sender itself .

[68 Firebird]

Yes I agreed tat dropping the idle rpm can drop psi at idle.
20 psi at idle is what I get in gear when motor is HOT and that's with 10W30.
Jumps instantly as rpms go up.

Gerry

[dataway]

Didn't get a bunch of fuel into the oil while working on the carbs did you? ... Can thin the oil out and cause a pressure drop.

[MNBob]

Mine was working, but rapidly jittering. I don’t know if that is what yours is doing or a more slow fluctuation. I replaced the sender and cleaned up the electrical connector and it still does the same thing. Maybe the guage?

[Johnny406]

After I pulled my motor and cleaned out the trash, I put the pump back on, hooked a pressure gauge up to the motor by the distributor (not the oil filter adapter), and submerged the oilpump pickup in a Tupperware type bowl of oil and I primed the motor to verify the problem was solved. My garage had a painted floor and I put some cardboard down because it's kinda messy but was well worth the piece of mind.

[rtanner]

Originally Posted by Johnny406

I had a similar problem a few years ago, there was a piece of Permatex about the size of a peeled thumbnail stuck in the pressure release.

This ^^^^^^ mine was infantile metal chip from who knows where, pulled pump drove out check ball, honed passage with a wheel cylinder hone, car has 30k miles on it now, no issues

[track73]

I had a similar problem with OP on the 79 TA. I dropped the pan removed the pump cleared the check ball and every thing turned out fine. I have since used the 9/16th balls and .060 shim to alleviate the problem. I have dropped the pan twice with no problems.

[Formulas]

Real oil pressure fluctuations are more gradual smooth up and downs a jittery gage is evidence of a indication problem..