What's up with my oil pressure?

[Talkwrench]

To answer a question; My motor can go up to 200, if its a stinking hot day and here it can do that easy, maybe beyond. I have 180 thermostats in as it should be.
I did have a mechanical aftermarket gauge in and now I have installed an electric type both saying roughly the same thing.

I may try the HPR 50 thats a 40-70. I have been using it in my Y block. Made a very small difference , Next time I'll try it in the Flattie, just I didnt want to go "too heavy" to start with as the motor is in good condition and didnt think it needed it.
Cant believe it could be Penrite oils alone causing this.

[G.M.]

All of my old Fords have 45 psi of oil pressure at driving speeds in hot weather and idle at 15. My 39 convertible has 115,000 miles on it. I have used Castrol 20/50 in it since start up and recently switched to 20/40 Valvolene Cummins Blue because of the additives in it. I expected to see a slight drop in pressure but didn't see any. Years ago when the engine ran at 200 + all the time the oil got black and burned some oil. Now that the engine runs at 180 the oil gets to a dark yellow and don't use any between changes. You have to see a pump with a leaky bypass valve or worn gears pumping oil to see the flow change. A bad pump or leaky valve will pump what looks like a good flow of oil out of an open hose but as soon as you put a SLIGHT restriction on the hose the flow almost stops. This is what happens in the engine and with low oil pressure you are not getting as much oil in the bearings and other parts. This bypassed oil is just dumped out of the pump not getting to the engine. You have to see the problem and what happens to understand it not just guess at what you THINK is happening. I have seen the problem in running engines and solved them. One in particular was a Lincoln V/12 with hydraulic lifters. This car belonged to Jack Armstrong a friend of mine from the AACA club. Jack asked if we would look at it for him. He trailered the car to the shop and we were looking for bad bearings or a leak. Pulled the pan and could find nothing wrong. We put pressurized oil in the sending unit hole with the pan off and expected a rain shower but had very little leakage from the engine. As this car ran for a while the oil pressure would slowly start to drop and the hydraulic lifter would start to play a tune. When the pressure got to about 7 or 8 lbs it sounded like a piano. We took the pump out and that's when I built the oil pump test unit. I removed the drive gear and ran the pump with a half inch drill. The pump direction is the same as drilling a hole. We started the pump and only put a 40 lb restriction on it. It pumped for a while and then the pressure slowly started dropping down to 8 lbs. We stopped the drill and started it again and the pressure went up and dropped again. We took the pump by pass valve apart cleaned it and it still dropped pressure so we made shim for on top of the spring out of 1/8" brass pipe and adjusted the shim until we got 55 lbs of pressure. As I recall the shim was about 3/16" long. Installed the pump back in the engine and Jack ran the Lincoln on several AACA tours and it always maintained 40 lbs or better oil pressure. These pumps will pump at 90 lbs pressure with no bypass valve. The by pass valve in the front of the engine has a flat on the bullet shaped end so no matter how strong the spring would be oil still drips out on the timing gear and is slung into catchers that lead to the oil pumps on the 37 to 48 engines. G.M.

[Talkwrench]

Shame there is not a "how too" on this GM thanks for the time in replying.
I have not seen how the pump operates on a flathead so Im working it out in my head.
I did shim up the bypass on my Yblock oil pump and it bought the pressure up a little but no matter what when the oil is hot pressure falls away, tried it on two pumps. I'd say the bearings have had their day. Thats just my experiance with shimming up a pump.

[31chevy]

Henry apparently did not worry much about oil pressure as there wasn't even an oil pressure or water temperature gauge in 34 pickups. Amp & fuel gauge only. ( I added oil pressure and temp to mine. semi hidden)
Gary.

[Old Henry]

Lest anyone get in a panic when their oil pressure drops off as the engine heats up or at low RPM's I share this from my operators manual for my '47:



I think of it more like an "idiot light". Any pressure is OK. No pressure is bad.

[ford3]

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LOL 31Chevy, not only was ford a briliant car maker, he was also very good at understanding human nature, he knew his engines ran hot and had low oil pressure at idle, so rather than worry the purchers about those things he just didnt put any thing on the cars to draw attention to those short comings, he built millons of cars and they went millions of miles, so i guess the running hot and low oil pressure really didnt matter

[VeryTangled]

https://www.fordbarn.com/forum/showth...=dupont+oiling