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Old 06-15-2016, 08:01 PM   #1
30-9
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Default Oil pressure

1939 - 59-ab two mech oil pressure Gage's - car starts and runs great. On start up oil gage pins on stock on after market goes to 80. After warms up idle 15 on stock 20-25 after market gage. After car reaches 190 degrees. Oil pressure is below 15 on both Gage's while driving. When stop at light both Gage's barely registers.

As mentioned car runs great - highway 60-65 no problem. Stop at light car idles as smooth as silk.

Should I be concerned?
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Old 06-15-2016, 08:41 PM   #2
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Default Re: Oil pressure

In my opinion 15 psi is plenty. Pressure just indicates that oil is flowing where it needs to go, not much else. At normal idle speed mine shows close to 0 pressure and my generator quits charging. So, I nudge the gas pedal a little until the generator starts charging, then the oil pressure gets above 0 and I know oil is flowing. Nothing to worry about in my opinion. I just drove mine to Alaska and back with those circumstances and no problems.
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Old 06-15-2016, 08:53 PM   #3
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Default Re: Oil pressure

Same as mine .. I do worry a little as when Im on the freeway [65] and its hot the oil pressure drops off not to 0 but its low...?? still keeps going though..
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Old 06-15-2016, 11:10 PM   #4
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Default Re: Oil pressure

Sounds normal for a well used 59 with a stock oil pump. By adding a .06 shim to the releaf valve gave me 50 psi cold. After warm up 0 - 5 psi idle and 15 to 20 psi going down the road. No strange noises and all 100 horses appear to be running in the same direction. Would I like to see more? Yeah. This one still runs quiet and strong. I'm not fixing what ain't broke.
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Old 06-15-2016, 11:41 PM   #5
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Default Re: Oil pressure

When comparing readings, and assuming everyone is using an 80 lb. pump, I think some considerations would be how recently the engine had been rebuilt, what viscosity oil one is using, that the oil line to the aftermarket gauge is full (no air), and when the engine is hot, what its operating temperature is.

I use 10w-30 oil, 160 stats; rebuild 35,000 miles ago. I recently hooked-up two different brands of oil aftermarket gauges. When running cold at 900 warm-up rpm's one read about 68 lbs other abt 72 lbs; stock dash gauge read at abt 1/3.

At hot idle 500 rpm both aftermarket gauges read between 18 and 24 lbs; dash gauge just above bottom mark.

Since the aftermarket gauges generally agreed and the dash gauge read below par, I first installed a (new) NOS 80 lb. oil sender unit .... no change. I then dropped the dash gauge down, removed its dial cover, and with engine running, re-calibrated the dash gauge to read the average of the aftermarket gauges.
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Old 06-15-2016, 11:57 PM   #6
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Default Re: Oil pressure

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I then dropped the dash gauge down, removed its dial cover, and with engine running, re-calibrated the dash gauge to read the average of the aftermarket gauges.
How did you calibrate the stock gauge? I've tried everything I can think of to do that without success. (https://www.fordbarn.com/forum/showthread.php?t=164760)
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Old 06-16-2016, 12:51 AM   #7
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Default Re: Oil pressure

You can only set the zero and the span (where the needle ends up when pressure sender is at 80lbs).
So setting it bo be correct at say 15lbs may give you a reading a bit of at 80lbs instead.
A bimetal isnt as accurate as a mechanical gauge its just an oilpressure indicator
And it takes very fine adjustments and a long wait between changes...dont be in a hurry.
Ill usually do it on the bench with lab power supply at 7.2v and an air regulator simulating the oilpressure, then you can go have coffee between adjustments instead of watching the needle move.
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Old 06-16-2016, 05:50 AM   #8
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Default Re: Oil pressure

Thanks guys.

Rebuild was about 35k ago. I use Rotolla 15-40 every 1000 miles. 170 stats and car never goes over 190. There is some small air spots in the tube of after market.

Glad to hear your feedback it set my mind at ease.
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Old 06-16-2016, 06:18 AM   #9
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Default Re: Oil pressure

My first car (in 1950) was a '36 Ford. In the following years i owned a number of different vintage flathead Fords and Mercury's and at one point owned eleven at the same time.
Other than looking occasionally to see if there was oil pressure present, I don't recall paying attention to what the pressure was.
I never had any engine problems that were related to low or high oil pressure.
Did I do something wrong? Should i have paid attention to what the oil pressure actually was so that I could agonize over it? Should I be punished for not doing so?
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Old 06-16-2016, 06:56 AM   #10
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Default Re: Oil pressure

Thanks 51. I'm not as lucky as you. I'm still asking (maybe dumb) questions, learning every day. Up till couple years ago, when I retired, I always had someone work on the cars. I never had the time. So I'm a novice when it comes to working/maintaining these wonderful machines. I always appreciate folks like yourself taking the time to teach me.
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Old 06-16-2016, 07:15 AM   #11
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Default Re: Oil pressure

my modified 8BA has a Melling19 oil pump with a washer shimming the relief valve.
I monitor the engine with Stewart Warner gauges . The oil pressure gauge is mechanical.
At cold startup it runs 60PSI, Hot idle is 15-20PSI, and cruising @65-70 MPH it's 70-80 PSI. I have considered removing the washer to lower the pressure.
When I was 16 my 50 Ford with a 53 Merc. engine ran the same pressure you mentioned. While I was away in the Air Force my father was driving the car and the crank failed. I always wondered if the low oil pressure had anything to do with the failure. I would check the sender and consider looking at the oil pump.
Just my 2..
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Old 06-16-2016, 07:21 AM   #12
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Default Re: Oil pressure

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Originally Posted by 30-9 View Post
Thanks 51. I'm not as lucky as you. I'm still asking (maybe dumb) questions, learning every day. Up till couple years ago, when I retired, I always had someone work on the cars. I never had the time. So I'm a novice when it comes to working/maintaining these wonderful machines. I always appreciate folks like yourself taking the time to teach me.
Nothing wrong with asking questions. Twenty six years ago, about six months before I retired, I purchased my current car as a retirement project and that's when I started paying attention to such things as oil pressure.
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Old 06-16-2016, 07:52 AM   #13
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Default Re: Oil pressure

30-9, sounds pretty normal to me. My stock 34 is close to your readings except a little higher pressure at hot idle of around 15 + PSI. I have a nice smiths mechanical gauge fitted. Nothing to worry about. Just drive it. Regards, Kevin.
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Old 06-16-2016, 10:20 AM   #14
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Default Re: Oil pressure

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Originally Posted by 30-9 View Post
Thanks guys.
There is some small air spots in the tube of after market.
Glad to hear your feedback it set my mind at ease.
Air transfers the pressure just the same as fluid. There is no oil in the tube when the gauge is bought and doesn't need any to work. If a little oil gets in there no problem. No need to "bleed" the line to fill it with oil.
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Old 06-16-2016, 11:03 AM   #15
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Default Re: Oil pressure

Air compresses and oil doesn't. Air can cause a shaky needle movement. I usually purge the air out of the gauge line while the motor is running by cracking the fitting to the gauge inlet. The King Seeley electrical set ups was relatively accurate since there isn't much to purge there.

I use all sorts of gauges for testing different aircraft systems and I have to take them to a metrologist at least once a year for calibration. We end up replacing a lot of the cheep gauges that won't calibrate to specs. It's best to have a good quality instrument that is within the range of movement needed. I have 0 to 30 psi all the way up to 0 to 2000 psi and most of the good quality metal case & glass lens instruments last a long time if they were made by reputable companies. The cheep plastic ones last about two years or so before they are no longer serviceable.

The old 41A oil pressure relief springs do fatigue with time. I would replace the spring and see what happens. If it needs shims after that then shim it up but 15 psi is within the range of normal operation for the pre-8BA engines. The 8BA engines generally have a bit more but not a lot more. I would rather see anything above 5 psi on a hot engine for the older ones at idle. Those old floaters were some good con-rod bearings but I wouldn't like to see the gauge at 0 psi anytime.

Last edited by rotorwrench; 06-16-2016 at 11:08 AM.
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Old 06-16-2016, 11:58 AM   #16
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Default Re: Oil pressure

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Originally Posted by rotorwrench View Post
Air compresses and oil doesn't. Air can cause a shaky needle movement. I usually purge the air out of the gauge line while the motor is running by cracking the fitting to the gauge inlet. The King Seeley electrical set ups was relatively accurate since there isn't much to purge there.

I use all sorts of gauges for testing different aircraft systems and I have to take them to a metrologist at least once a year for calibration. We end up replacing a lot of the cheep gauges that won't calibrate to specs. It's best to have a good quality instrument that is within the range of movement needed. I have 0 to 30 psi all the way up to 0 to 2000 psi and most of the good quality metal case & glass lens instruments last a long time if they were made by reputable companies. The cheep plastic ones last about two years or so before they are no longer serviceable.

The old 41A oil pressure relief springs do fatigue with time. I would replace the spring and see what happens. If it needs shims after that then shim it up but 15 psi is within the range of normal operation for the pre-8BA engines. The 8BA engines generally have a bit more but not a lot more. I would rather see anything above 5 psi on a hot engine for the older ones at idle. Those old floaters were some good con-rod bearings but I wouldn't like to see the gauge at 0 psi anytime.
Not trying to be critical but got a chuckle and a vision of little yellow birds using "cheep" gauges.
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Old 06-16-2016, 12:12 PM   #17
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Default Re: Oil pressure

No matter how you say it crap is crap in the end. It'll end up like the yellow bird, with the yellow bill, standing on the window sill Jody Jingle. For those that never marched to that tune, lets just say it ends up in the crapper.
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Old 06-16-2016, 03:50 PM   #18
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Default Re: Oil pressure

Yo 30-9. Do a compression check and you'll know the current condition of your engine. If the readings are good, put a piece of masking tape over your oil gauge and enjoy the ride, worry free.
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Old 06-16-2016, 04:19 PM   #19
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Default Re: Oil pressure

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Yo 30-9. Do a compression check and you'll know the current condition of your engine. If the readings are good, put a piece of masking tape over your oil gauge and enjoy the ride, worry free.
Really......I can't wait to hear how a compression check shows the condition of bearings. DD
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Old 06-16-2016, 07:39 PM   #20
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Default Re: Oil pressure

We tried the masking tape trick once and it worked great. Then after 50 or 60 miles we both looked at each other and thought ok this doesn't smell too good as steam poured from the radiator. Ok it was tape over the temp gauge not the oil. Let it cool and were good to go again.
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