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Old 09-17-2013, 01:14 PM   #1
Modelacrazyq
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Default Low oil pressure

Hoping some flathead gurus can offer some tips for a novice. My '41 engine doesn't Carry good oil pressure, maybe 25psi cold. I bought the engine used, brought it home, and built a cradle for it and a radiator. First thing I did was drop the pan and clean out 1/4" of gray peanut butter out of the pan, pickup, and pump. I put fresh 10-30 in it and to my surprise got it fired up and idling well. The low pressure concerned me since my 8ba runs 60psi cold. So I installed a new style Melling pump and F-1 style pickup tube in the pan. Same result. Am I missing something?
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Old 09-17-2013, 01:19 PM   #2
Lawson Cox
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Default Re: Low oil pressure

25 pounds pressure when cold doesn't[t sound strange to me.
In fact, that is pretty good oil pressure when cold.
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Old 09-17-2013, 01:29 PM   #3
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Default Re: Low oil pressure

I assume the floating bearing engines don't carry pressure like the 8ba engines. I did take the oil pressure gauge off and left the tube in the block just to see oil at least moving, which it is but it just kinda pees a weak but steady stream. I guess it's better than no oil! The engine doesn't knock or rattle, only a couple of ticking lifters.
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Old 09-17-2013, 02:25 PM   #4
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Default Re: Low oil pressure

Two thoughts:

First, your gauge may not be reading accurately. I've had enough bad senders to know. You could hook up a cheap mechanical gauge temporarily just to see. Here's how I did it and found out my pressure was fine. https://www.fordbarn.com/forum/showthread.php?t=68156 Replaced the sender and the gauge read fine.

Second, pressure is not as important as flow. Any pressure indicates flow as you have seen. That's all that's really necessary - to get the oil where it needs to be. As Lawson said, 25 psi is certainly within what I would call normal range.
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Old 09-17-2013, 02:47 PM   #5
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Default Re: Low oil pressure

I have a cheap parts store gauge on it, and I just spoke with a fiend of mine who suggested checking the spring in the relief valve in the front of the block. Apparently 59 style engines have a relief on the pump AND in front of the oil gallery.
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Old 09-17-2013, 02:50 PM   #6
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Default Re: Low oil pressure

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And 25 pounds is when it's revved up, at idle it has very little pressure, although there is oil moving because when I took the gauge off it will squirt oil out of the tube.
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Old 09-17-2013, 03:08 PM   #7
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Default Re: Low oil pressure

ford does not give an oil pressure reading at idle, ford says #30 at 30 mph with a warm engine, oil flow is more important than oil pressure, 5 gal per min at #5 pressure is a hell of a lot better than one qt per minute @ #100, oil flow to moving parts is what keeps your engine alive

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Old 09-17-2013, 03:18 PM   #8
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Default Re: Low oil pressure

I have found earlier posts on this subject, they all seem to point in the same direction- the check valve in the oil gallery. In those posts they mention shimming the spring to increase pressure. The pump is definatley moving oil in this engine but I'm thinking the relief in the gallery is canceling out the 8ba pumps ability to produce pressure. There is no telling how many miles are on this engine but is like to keep it alive as long as I can.
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Old 09-17-2013, 03:20 PM   #9
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Default Re: Low oil pressure

And thanks to all for the feedback, it is much appreciated from a guy just learning the flathead ropes!
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Old 09-17-2013, 08:26 PM   #10
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Default Re: Low oil pressure

I leave both reliefs in the engine... The engine doesn't need to produce a lot of pressure to work properly. My 59AB runs 60 lb. at speed hot and 33-5 lb. hot at idle, but it's practically new- 8ba pump with the pressure relief and has the valve up forward also.
You might want to see that the pressure relief valve spring forward is intact, but I would not shim it, or stretch the spring... If you have the original pump, you may want to replace it with the 8ba pump... I run good used pumps, new ones that are good may be hard to find...
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Old 09-17-2013, 09:18 PM   #11
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Default Re: Low oil pressure

I have a friend that has #5 at idle and #20 on the road, been that way for the last 10 years and still ggoing strong. Besides 60 lbs hot will sand blast your bearings and caise more harm.
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Old 09-17-2013, 09:44 PM   #12
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Default Re: Low oil pressure

Quote:
Originally Posted by Ol' Ron View Post
I have a friend that has #5 at idle and #20 on the road, been that way for the last 10 years and still ggoing strong. Besides 60 lbs hot will sand blast your bearings and caise more harm.
Ol Ron, my C59A runs 60lbs hot on a mechanical guage. Are you suggesting I should lower my pressure to ease up on the bearings? If so, how?
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Old 09-18-2013, 12:56 AM   #13
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Default Re: Low oil pressure

If you want to increase your oil pressure restrict the flow of the oil.
Now you know that doesn't make any sense but that's exactly how pressure and flow relate. Higher pressure does not necessariy mean higher flow. It may just mean more restriction in the lubrication system - which is bad. I'll take flow over pressure any old day.

Think about your garden hose. If you want to fill up a bucket which is quicker? Just let the hose run full blast out the end without any nozzel to restrict it? or put a nozzel on it and screw it down so that you get a real powerful violent stream? Yeah, to some extent the lubrication system works the same way.
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Old 09-18-2013, 07:16 AM   #14
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Default Re: Low oil pressure

When the relief valve spring is weak oil at the end of the line is just flowing out freely and oil is not being forced through the tight bearing surfaces. If the relief valve in the pump is leaking the oil from the pan though the pump is dumping oil right back into the pan providing less oil to the bearings. Booth relief valves can be adjusted with a shim on the spring. The front one can be adjusted with a pressure gauge and spinning the engine with 12 volts either in the car or sitting on the floor. You need to make a simple tester to test the pump and set the relief spring in the later pumps w/bypass. You can make a simple tester. I wouldn't put any pump in an engine without testing it. G.M.
The tester shown was the first one and the pump is driven by a 1/2" drill motor running in the same direction as drilling a hole. The white plastic tube is bored out on each end a few thousanth's smaller then the 2 shinny area's shown on the pump. The plastic is tapped on with a soft hammer sealing both ends. A quart of oil is put in a pan and the pump pick up down in the oil the drill is started. The oil will pump and flow out the plastic tube back into the pan. There will no pressure on the gauge or very little. Bend the tube and the pressure rises the more it is bent the higher the pressure. These pumps will put out over 90 lbs. The relief valve in the front of the valley is like bending the plastic tube. On the pumps with the relief valve on them as you restrict the flow and the pressure go's up the spring in the valve controls the output flow and pressure. Fully bent the pressure shown is the pressure supplied to the engine. The spring can be shimmed with a shim cut from 1/8" pipe. Start at about 1/8" long and adjust the length for the pressure you want. I set them from 45 to 50 lbs. We had a Lincoln V/12 that dropped in oil pressure after a while. Shut it down and restart and the pressure was back up for a while and slowly dropped. This had nothing to do with heat. When we built this first tester and put the Lincoln pump on it the pressure was good for a few minutes then started dropping slowly. Shut the drive drill down and the spring relaxed, pressure went back up and after a few minutes started back down. We shimmed the pump and got the pressure to 50 lbs. The owner drove the car on tours for a number of years and the pressure stayed at 50 cold I don't remember the hot pressure but it stayed up pretty good. You can turn these pumps by hand with the pick up in oil and they will pump oil in 2 turns. Don't be fooled by this as we had one like this for Skips 34 P/U. He said that looks like a good one. I said we have the tester let's check it. On the tester as soon as you put the slightest restriction on the tube the oil just slipped in the pump with no pressure showing. This was the old type pump with no relief valve. Either the end plate clearance was to much or the gears were worn. We had plenty of old pumps so we just tested another one. G.M.
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Old 09-18-2013, 07:42 AM   #15
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Default Re: Low oil pressure

You say you have the 8BA pump with the truck pickup tube. That is a good pump, I use it in all my engines. I would shim up the spring on the up top valve and just let the pressure valve in the pump do it's thing. I would also use 15-40 oil. Walt
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Old 09-18-2013, 08:27 AM   #16
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Default Re: Low oil pressure

The more wear you get on the main and rod bearings, the lower the oil pressure will be. The 8BA family of engines had no lifter galley oil psi relief valve. They only had the one in the later type oil pump. Shimming or replaceing the spring in the galley relief valve will bring the pressure back up as long as the crank and cam bearings are still in fair condition. This stuff doesn't last forever. At some point old flatheads need an overhaul. If you put a real heavy spring in the upper valve, the oil pump relief valve will regulate it as high as it will ever go. If it is still low after that then I'd figure the bearings are worn excessively.
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Old 09-18-2013, 08:59 AM   #17
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Default Re: Low oil pressure

That's about when the bearings start to talk to you. G.M.
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Old 09-18-2013, 10:19 AM   #18
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Default Re: Low oil pressure

I found that I could get about another 5 lbs. pressure using S.A.E. 40 oil which is OK for starting temperatures above 60.
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Old 09-18-2013, 11:36 AM   #19
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Default Re: Low oil pressure

I have used Castrol 20/50 in my old Fords for 33 years. Better oil pressure.
The water pumps on 32 to 48 had bushings and oil that is to thin weeps out behind the pulley. 120,000 miles on my 39 since start up. Still quiet, burns no oil runs good and no sludge. I live where it's 90 most of the time so getting to thick is not a problem. G.M.
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Old 09-18-2013, 01:02 PM   #20
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Default Re: Low oil pressure

My plan is to remove the intake and shim the spring. It makes perfect sense seeing as how ford set the valley relief at 30psi, and 60 years of wear and tear would weaken the spring. I am using 15-40 rotella oil but from what I've read even that oil has reduced levels of zddp to protect catylitic converters. Valvoline VR-1 Racing oil looks like the best option( I'm sure we could go on for days on this!) but I am for sure shimming the relief valve so the pump will regulate the pressure. Awesome info guys, many thanks!
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