1977 302 low oil pressure

[mkemark]

Working on my 1977 with (what I'm pretty sure is) original 302. Oil pressure gauge was showing very low reading, about 5 psi, and never moved with engine RPM. Tested out the gauge, gauge is good. I figured it was the sender as it looked pretty banged up. Replaced sender and got same 5 psi. I have driven it only a few times. When starting, it runs rough (probably due to carb) but doesn't have any concerning engine noises. After warming up and driving the first time, started to get valve train ticking. This happened again a second time, dumped a quart of Mystery Oil in and it seemed to go away for the ride home with the engine at temp. Drove it again the other day and the valve train ticking came back with a vengeance. No other ideas so I pulled the oil pan. The oil filter, pickup, and pump had oil in them. The pump and pickup looked to be connected properly, and there was oil coating the engine low end parts. I pulled the oil pump and disassembled, noticed some spacing in the pump gears (need to get feeler gauges tomorrow to measure). It looks to be the original pump with god knows how many miles (my truck was on this forum years ago by a P.O. stating the odometer showed 90k, now the odometer shows 53k).

I have a replacement pump and am planning on installing it, but I also hear a lot of people say that oil pump failure is rare. I'm not leaking oil in any noticeable amount and the oil didn't have any signs of antifreeze or anything else when drained.

Before I put this thing back together, is there anything else I should check, inspect, measure, etc to see if I can localize the problem or just strap on the new oil pump and pray?

 

[73azbronco]

put a test pressure on the sensor that you know is accurate, then see what the gauge reads vs what your input says.

 

[gnpenning]

If you have the pan off, pull a couple rod caps and maybe a crank cap. Take some pictures and post.


Low oil pressure can be a pump issue or excessive clearance in bearing areas.

A mechanical gauge will be your friend.

 

[B RON CO]

Hi, as mentioned, I would pull some bearing caps. If the bearings show copper color, the bearing is worn. You may also use Plasti-gauge to check bearing clearance. If the bearings are not worn too bad, you can run thicker oil like 20W-50, and add Lucas Oil Stabilizer.The ralityis, it might be time for a rebuild. In addition to the oil pressure gauge, I would get a compression tester. Good luck

 

[Broncobowsher]

Original pump would have been an aluminum housing. The replacments are cast iron. Easy way to tell.
Was there any glitter to the oil?
Can you see the timing chain? Super sloppy?
Find some videos about checking for a flat cam lobe. If you got a sudden lifter tick after putting solvent in the oil I would suspect that.
Low oil pressure on an otherwise decent engine I will attribute to worn cam bearings.

Pulling the oil pan off is the start of opening the can of worms on an old engine. Either things will be great, or you will be going through layers of onion.

 

[mkemark]

Hi, as mentioned, I would pull some bearing caps. If the bearings show copper color, the bearing is worn. You may also use Plasti-gauge to check bearing clearance. If the bearings are not worn too bad, you can run thicker oil like 20W-50, and add Lucas Oil Stabilizer.The ralityis, it might be time for a rebuild. In addition to the oil pressure gauge, I would get a compression tester. Good luck

If I check the clearances on the rod and main bearings, what numbers am I looking for? I can look up standard clearances but at what point should I start looking at pulling the motor?

 

[73azbronco]

I'd double check pressure reads correct, do you have a mechanical gauge you can try? Easier than busting crank caps and plasti gauging.

Battery voltage? IVR voltage?

I have to add if its making that racket, at that age, motor is most likely done.

 

[mkemark]

Pulled a main cap and rod cap. Copper on the main bearing, not really on the rod. I'm thinking it's probably not good news. I'm going to plastigauge the caps tomorrow hopefully.

 

[73azbronco]

seeing copper=significant wear.

 

[gnpenning]

No need to plasti gauge, unless you really want to. Time to be thinking about either a rebuild or replaced.

 

[B RON CO]

Hi, you can remove the bearing shell from the cap and see if it is original or if the crank has been cut undersize. Too late for a compression test, but the odds are, the engine is worn out. Good luck

 

[bmc69]

Excessive cam bearing wear is usually responsible for the majority of oil pressure loss in a high mileage 289/302 engine. Of course, main and rod bearing wear contributes as well.

 

[Apogee]

Sloppy...good with a "Joe", not so good with a main bearing.

 

[Speedrdr]

I’d be surprised if the engine wasn’t making a metal on metal squeal.

R

 

[73azbronco]

This is where STP accels...

 

[Broncobowsher]

This is where STP accels...

Until that cold morning and the oil pump driveshaft twists into a candy cane.