Oil pressure trouble?

[mike p.]

I have had my Shell Valley for about a year and half.
It has a rebuilt 1973 429 that has been pretty much trouble free for 4800 miles.
In the last week I have noticed a great fluxuation in oil pressure. It can start out cold with 70 lbs showing on the guage, and after 20-30 minutes of driving it can go down as far as 0.
The pressure will come back up to 20-30 lbs after a short time, but will never get as high as it was earlier.
I never hear any rattles or knocks, and the engine never gets hotter than usual.
This problem seems to have started after I put a remote oil filter on earlier this summer?
I'm using 10w40 oil and a NAPA filter, and there are no oil leaks anywhere.
I tried a different oil guage today with the same results.
I'm thinking a bad or going bad oil pump???
Anyone have any suggestions or advise?
thanks in advance, Mike P.

[Dangerous Doug]

Check the oil pressure gauge tube for leaks. Check for leaks where the gauge tube connects to the block. Also, feel behind the dash on the back of the gauge for any oil. Chances are you have a leak somewhere, and this can be easily fixed.

DD

[jhv48]

Since your problem seems to have started after the addition of a remote oil filter, I would first return the oil filter back to its stock location and see if there is a change back to your normal oil pressure. If so, you have isolated the problem to the remote filter.

[mike p.]

I have checked for leaks, and found none.
When I bought the car (finished) it had the shortest filter that NAPA had.
You could not get the filter off without bending it up to get it past the frame.
Needless to say a new one would not go on with removing the bolts from the motor mounts and jacking up the motor or using a remote filter kit.
I chose to use the remote kit, and it has been trouble free for at least 2 months.
Thanks for the ideas so far, and I sure hate to think about dropping the pan for a new oil pump, but????

[Rick Parker]

Is it possible you have the hoses attached incorrectly to the filter head, thereby attempting to force oil backwards through the filter?

[mike p.]

The hose's are installed correctly, and oil pressure has been Ok until just a few days ago.
Thanks

[Rick Parker]

Maybe the bypass is stuck partially open in the pump, or maybe the pickup tunbe is cracked? 385 series seem to have oiling issues sometimes.

[strictlypersonl]

I second Rick's suggestions, and would add a possible loose pickup tube.

[YerDugliness]

I had the front cover gasket on a 302 "disolve", for lack of a better term, and the resulting paper shards found their way into the pan and clogged up the screen on the oil pump's pickup. It acted exactly the same as you describe...no clicking lifters, no knocking bearings, just low oil pressure until I shut it off, at which time the absence of vacuum allowed the shards of paper to drop off the pickup screen, only to be sucked back up once the engine was fired again.

The engine was in a Fox-body T-Bird, but I managed to replace the pickup by lifting the front of the motor and dropping the oil pan far enough to get a box-end wrench in there. The engine ran just fine after that.

I'd try all the other suggestions, though, before I started taking motor mount bolts loose and scarring up your hands like I did...it was not a pleasant job.

Cheers!

Dugly

[63mercury]

Try dumping the napa filter and using a quality Motorcraft or Purolator brand filters. I have had many challenges with napa filters in the past.

[mike p.]

I did have a fram filter on there since I installed the remote filter with no issues.
I changed to the NAPA about 3 days ago.
Seems to be the same problem so far.
If I have to drop the pan I plan on a new oil pump for sure--just because.
Thanks

[dcdoug]

Don't use Fram filters either, they are poor quality. Whole threads have been written about them on this forum. I'd put a motorcraft filter on there to start.

[tirod]

Cheapest thing to do - change the filter to a reputable high quality brand. High production, low cost filters can and have been a disaster.

No matter what the brand, a bad filter with loose internal parts does exactly what you describe - oil pressure is all over the gauge, and you can lose a rod out the side of the block.

When the replacement motor started doing it too, 6 months later, I was told, change the filter to a good quality brand. I did, and it stopped immediately.

Until you change the filter - a $6 item - you can't be sure that it isn't the problem. But if it is, it can destroy a $6000 motor - or more.

Cost me $1,800 to learn that lesson, I won't buy inexpensive filters. And I won't buy my own house brand, it's the same maker.

[MaSnaka]

If your out of ideas and you have an electric sensor/guage...you didn't mention...check the wiring. I chased a low oil pressure issue for a long time before discovering that I had a wiring problem. I now have a mechanical guage.

John

[bobcowan]

As said above, use a quality filter like Motorcraft or Purolator Pro-1.

There have been some basic design flaws with the Lima motor's oiling system. It was designed as a truck motor, and there are some problems in using it as a performance motor. BUT, Everything has been fine until recently, so clearly something changed. The trick is to find out what happened.

Fluctuating pressure like that usually means you're sucking air or the intake track is blocked. That's a bad thing. Don't run the engine for another minute like that. Pull off the pan, remove the pump and pick up. Clean it all up and see what you got.

It could be a clogged pick up screen, broken pick up pipe, etc. Don't put it back together until you find out what the problem was.

[Dangerous Doug]

Okay, I'm drawing on years and years of memory here, but:

When I was in high school I briefly drove a '53 baby window Volkswagen Beetle (Hey, now! That was pretty cool back then!) Anyhow, with the high performance engine I had a remote oil cooler, and I HAD to run a high volume oil pump with the extra lines or risk blowing up the engine.

Okay, let's say Mike P.'s engine has a standard volume oil pump to begin with, and then he adds a remote filter. Should he also upgrade the oil pump to a high volume pump?

I've received many answers to this question, the most authoritative was to not use a high volume pump, but use a "precision" oil pump with standard volume. Melling makes a precision oil pump.

What say ye?

First, when adding a remote oil filter or cooler, is a high volume or precision oil pump upgrade necessary?

Second, which is best: High Volume oil pump; or, standard volume precision oil pump.

Incidentally, for my current 331 build I've purchased a precision oil pump. I do have a vague sense of uncertainty in that Keith Craft, my shortblock and heads source, uses a high volume pump...

DD

[Jerry Clayton]

When you build a high performance engine with increased clearances for increased oil ing you then need a pump with increased volume capacity---sorry for using the words high performance and increased in the same sentance

[Jerry Clayton]

ALSO---------there have been instances of valve seal deteration and break up into little pieces that then blocked the oil flow return path in the cylinder heads and valley under the intake so that the oil can't get back to the pan---removing a valve cover will expose evidence of this

Also, when this happens, particals will find there way down and into the pickup screen on the oil pump blocking flow into the pump

[madmaxx]

If you go high volume you must have a 9 quart pan or you will suck it dry. Mellon high volume pump M83HV has a max flowrate of 8 Gallong Per Minute at 6K rpm and 4 gallons per minute at 2000 rpm's. The mellon tech actually indicated it flowrate peaks at about 4K rpms and stays flat until 6k rpm. I assume because the net positive suction heads availabe limits flowrate.

[Jerry Clayton]

A fact that most of are overlooking is that an oil pump will not pump more oil up/around/thru an engine than the clearances will aloww to pass---the pump has an relief valve that will bypass the oil flow and it will stay right in the pan---
Biggest issue with high volume/hipressure pumps are blowing oil filters when cold-----