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I have a 47 Custom Super Clipper, 356 OD That is having low oil pressure readings. Car has 59,000 miles on the odometer. Did some engine work 5 or 6 years ago
Just got everything together and ready for the road.
Start the engine and it takes about 30 seconds for the oil pressure gauge to go up to about the 40 mark. Driving the car at in town speeds the gauge reads at the 40 mark. As the temperature warms up, the oil pressure reading drops.
I took the 47 on a 10 mile loop yesterday. Pressure started out at 40 when the engine was cold. As were progressed on the loop, country roads at 40 mph, pressure still about 40.
Operating temp right on the center of the gauge. on the highway part of the loop, 55 mph and everything getting warmed up, the pressure dropped a bit. When I got back to my garage the oil pressure was just off the low peg, maybe about 5 to 10 lbs. I only have about 50 miles on the engine work.
When I bought the car about 8 years ago. I don't remember anything about the drop off in oil pressure. Been working on the car for about the last 7 or 8 years.
Engine work done:
New rings, standard size; All new valves, valve springs, New
lifter inserts, New standard size rod bearings, new water pump, Rebuilt starter and generator, new electrical parts,
new wiring.
After the mechanical work was done, the car went to the body shop for the body work and paint.
Brakes, tires and interior also completed.
Now I want to drive the 47, but the oil pressure is the problem. Where do I look next. New oil pump? New oil pump pressure bypass spring. Different oil? I am trying
a straight 40 weight now. I was using a 30 weight to start
out with last year.
The temperature stays right in the middle of the gauge.
Any new ideas??

Lauren R Lampi
Grand Rapids, Minnesota

Before buying or changing anything with the engine, I would get a mechanical gauge and use that to verify that the electrical sender and gauge is reading properly. After almost 70 years there could be some issues. My mechanical is semi-hidden in engine compt but will be permanent. For convenience, I used one of the 1/8" plugged ports toward the rear of the main gallery on pump side of engine as the connection point. My mechanical gauge reads about 50 at that point. Don't have the dash in or electrical gauge hooked up to verify what if any difference there might be but at least I am confident there is pressure.

If you do as HH56 suggests with a good quality mechanical gauge and the pressure is indeed low (should be about 45 psi at road speed), the first two things I'd check, given the engine work you specify, is:

1. Thickness of the oil pump cover gasket. You want the thinnest possible consistent with sealing the cover. An excessively thick gasket will just allow the oil to short-loop within the pump cavity and never reach the galleys. I usually make the gaskets from notebook paper - 0.003 - 0.005" thick.

2. Examine the oil pump cover to see if has a wear pattern from the rotating gears. If so, it gives the same result as too thick a gasket, the oil just loops within the cover and never enters the outlet stream. If there is any wear pattern you can feel with a finger nail, take the cover to a shop and have it resurfaced.

If the max pressure you can get with a cold engine and proper viscosity oil is 40 psi or less, I'd shim the spring on the pump relief valve with a thin washer (no reason but buy a new spring) and aim for a max pressure of 45 before the pump relieves the pressure.

Just want to underline what Owen said about the thick oil pump cover gasket. Back when your engine was done, most of the gasket sets were coming through with thick cover gaskets. I like them to be only about .002-.003" thick. A quality piece of stationery will do nicely to make one.

Oil pressure of my '47 Custom Clipper was similar to what you described. I shimmed the pressure relief valve spring with a couple of flat washers. This fix increased oil pressure by about 20%. It runs about 50+ lbs at cruising speed (was about 40 lbs) and drops to about 15+ lbs when thoroughly warmed up and idling (was around 10 lbs). Never heard any lifter noise so they were and are getting enough volume and pressure. I run 15W-40 oil. The engine is equipped with a Fram oil filter. I have an auxillary mechanical oil pressure gauge connected as HH56 describes. I still have the original electric gauge connected. It reads a bit pessimistic compared to the auxillary gauge. Try the shimming fix and recommend going to 15W-40 oil and new filter element.

(o{}o)

Thank you to everyone that replied to my low oil pressure problem. I like the "answers" that you all provided.
On Monday I am checking out the local parts stores for a
Mechanical auxiliary gauge for under the hood as was
suggested. Also I will shim the spring in the oil pump.
I have three gallons of Rotella 15-40 on the shelf and a new filter, so time for a oil change. I live in Northern
Minnesota, so our vintage car driving time is limited.
The reply's are appreciated..... It is great to have this
Packard form to get help on Packard "problems".

Lauren R Lampi

Garage day today. Ordered the gauges and parts for a mechanical oil pressure gauge under the hood.
I removed the oil pressure relief spring that I had placed one washer when I did the engine about 4 or 5 years ago.
I put in two regular thickness washers and did a short test drive. I still had pressure at 40 pounds and after driving and getting the car warmed up, the idle oil pressure was in the 10 pound range. Tomorrow I will Add and one more washer to the spring and check the results.
Another item I found while I was under the car........
Loose tie rod ends both L and R. I can't remember if I had forgotten to put in the cotter pins when I had assembled the front end 4 or 5 years ago. Maybe they were taken out when I had the front end aligned last fall and not replaced. I tightened the nuts on the tie rod ends and put in new cotter pins. I'm really glad I found this before getting the car on the road.
Changed the light bulbs also, Headlights, tail, park, and turn signals for halogen bulbs. Hope that these are brighter.

Lauren R Lampi
Grand Rapids, MN

If your lights are dim, check grounds. Especially your battery ground. Also, did you use 6v cables or 12v cables???
Many, many people make the mistake of using 12v cables, thinking 12 is better than 6. It's just the opposite.

Garage day today. Overcast and sprinkles of rain. Working on the low oil pressure situation. I took the oil pressure
bypass spring out and added two more washers. Total of four washers now. Ran the car in the garage ( door open )
to check what the dash oil pressure gauge was reading.
The gauge read over 40 pounds....Maybe about 50 at high idle. Ran it for a while. Idle pressure was about 20 to 25 pounds. The mist and sprinkles stopped later on.
Took the 47 out for a short spin to get it warmed up and check the pressure. Oil pressure read over 40 while
driving around the empty high school parking lot that is near my home. At idle when I got home reading was about
the 25 range. When I get all the parts for the under hood oil pressure gauge, I will install it as suggested.

Yes, West ...... I'm running the new "monster size 6 volt"
Cables for Positive and Negative. Also, a heavy cable from the lower bolt on the starter to the frame as an additional
ground...Also the Parking light fixtures, the tail light fixtures and the license plate light fixture are all grounded to the frame with a heavy wire.

My 1950 Packard had low oil pressure after I got it. I put in an auxiliary gage and found the pressure on that gage was not low and about double what the original gage said. I bought a nice Stwart Warner "wings" gage set that looks correct in the car and mounted it under the dash.

I am concerned that some of the advice you are getting may not be correct. I totally agree with getting the excess clearance out of the oil pump. However shimming the pressure relief valve will only change the pressure when cold, and the problem is when the oil is hot. Excess oil pressure when cold puts more stress on the pump and could create leaks anywhere there is pressure. I would not do that.

The oil you are using (straight 40 weight) would have more viscosity change with temperature than a multi-viscosity oil like 10W40. You could even try a higher viscosity than that depending on the weather. The multiviscosity oil should be used on any car that has a large viscosity change with temperature.

Also another thing I learned over the years in engineering is to make only one change at a time between tests. If you change more than one thing you will not learn what change did what from the test.

Good luck.