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Old 03-23-2020, 08:54 AM   #1
Mulletwagon
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Default Oil Pressure - OK

Have a fear of driving the old Henry not realizing that I may have no oil pressure. The typical answer would be to install an oil pressure gauge which would provide an easy check and also gives some indication of the health of the lube system and state of the bearings. As a minimum, I would prefer to just install an idiot light. As I recall, idiot light switches break ground at about 8 psi which may be a little high for Model A engines where oil pressure is usually less than 10 psi. Anyone know of a light kit set up for As or have any experience setting one up from off-the-shelf components ? Is my concern unfounded ?
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Old 03-23-2020, 09:48 AM   #2
30 Closed Cab PU
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Default Re: Oil Pressure - OK

The Stock A does not have a pressurized oil system. Most of the time an oil gauge only reads 2 lbs. or less, unless the oil is very cold and then only reaches 4-5 lbs. max. while cold. The oil pump is capable of much more pressure (60-80lbs., I forget), but since the system is unrestricted, no pressure.
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Old 03-23-2020, 10:10 AM   #3
1931 flamingo
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Default Re: Oil Pressure - OK

X2
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Old 03-23-2020, 10:25 AM   #4
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Default Re: Oil Pressure - OK

It is a splash system from the model T days with the addition of an oil pump to get the oil up high. Gravity brings it down but also imagine what it looks like in the engine at driving speed, it would be like putting oil in a blender, the stuff is everywhere even a mist is everywhere, the whole engine is saturated with oil splashing and misting. I don't worry about mine unless the dip stick shows no oil.
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Old 03-23-2020, 10:27 AM   #5
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Default Re: Oil Pressure - OK

An oil pressure gauge on a Model "A" only indicates the oil pump's output pressure, and not the pressure of the oil feeds to the bearings in the motor. There's one exception, and that is the center camshaft bearing which is pressurized directly by the oil pump. So an oil pressure gauge on a stock Model "A" engine is mainly a decoration.
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Old 05-29-2020, 11:30 AM   #6
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Default Re: Oil Pressure - OK

Quote:
Originally Posted by 30 Closed Cab PU View Post
... The oil pump is capable of much more pressure (60-80lbs., I forget), but since the system is unrestricted, no pressure.
Guten Tag,
are there a pressure / RPM chart or certain measuring points available?
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Old 05-29-2020, 11:59 AM   #7
Jim Brierley
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Default Re: Oil Pressure - OK

Guten morgan Werner! No oil pressure in the Model A, so no chart is available. Model B's have pressure to the main bearings only, less than 1 pound when hot, so no chart for them either.
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Old 05-29-2020, 12:03 PM   #8
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Smile Re: Oil Pressure - OK

I have always added an oil pressure gauge.

Here is my reason for doing so.

Many, many years ago after dropping the oil pan on my first Model A, also my first car. When we re-installed the pan, we did not know the oil pump was not properly fitted into position.

On my way home from the ESSO station where we did the work and I worked part time after school. I noticed there was “NO” reading on oil pressure gauge. Turned around, and went back to garage. Put car back on life. Removed pan and re-installed pump correctly.

Put pan back on. Re-filled with oil. Started car. Oil pressure back to 3 to 5 pounds. No known damage done.

60 years later. I still feel the need to known that oil is flowing up to the valve gallery, cam shaft, timing gear, and bearings.

Cheap insurance and gives me another thing to look at. Our car is stock with the exception of oil pressure gauge, WW tires, leak less water pump, oil breather, and generator tension adjuster.

Enjoy.
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Old 05-29-2020, 12:21 PM   #9
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Default Re: Oil Pressure - OK

The old air cooled VW pressure switch is much lower pressure--- think 1-1/2---- used to use them on cars that the oil pressure light would blink at hot idle
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Old 05-29-2020, 02:02 PM   #10
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Default Re: Oil Pressure - OK

Thanks for the hints. I think I wrote a misunderstanding question.

I did not mean the delivery pressure in the open line. Rather, I mean the pressure that the pump with a closed outlet pipe delivers.
Quote:
The oil pump is capable of much more pressure (60-80lbs., I forget),
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Old 05-29-2020, 04:01 PM   #11
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Default Re: Oil Pressure - OK

Quote:
Originally Posted by Werner View Post
Thanks for the hints. I think I wrote a misunderstanding question.

I did not mean the delivery pressure in the open line. Rather, I mean the pressure that the pump with a closed outlet pipe delivers.
Since the gear pump in the Model A is basically a positive displacement pump that has no relief valve with a closed outlet I can imagine it would continue to build pressure until it hydraulics and either stops or breaks something.
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Old 05-29-2020, 05:48 PM   #12
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Default Re: Oil Pressure - OK

Vw oil pressure switch 7.5 lbs

The model a engine uses a pump, splash and gravity fed lubrication system. The pump lifts oil into the valve gallery (behind the valve cover,behind the carburetor) the gallery had dams that trap the oil which splash lubricates the valve lifters springs and guides. The oil also flows from the pools down to the main bearings and cam bores through tubes and drilled ports to the cam.Oil pump flow is high enough to keep these pools constantly full of oil,the excess drains back through the drain tube and a hole knocked in the block above the timing gear lubricating the gear teeth,this oil then drains into the dipper tray where the rod bearings are fed by dipper cups that pass through the dipper tray oil, the rods passing through the dipper tray creates the monsoon effect of oil spray present when operating

The ford system used in the model a is very effective,you do not need pressure to create the hydrodynamic principle to lift and support the crankshaft on film of oil,constant flow is sufficient to protect the bearings.Dipper rod lubrication is good to 4k rpm,any faster and the cup moves too quickly to pick up oil.

An oil pressure gauge is a novelty,when cold starting an engine you can hear the dry valve train,it takes about 15 to 30 seconds to fill the valve galley..you never want to fire up and drive an a engine,give the pump a chance to fill the valve galley before you put a load on the engine.basically let it warm up a bit at 500 rpm or so
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Old 05-29-2020, 07:36 PM   #13
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Default Re: Oil Pressure - OK

All good info. The key question is - if driving along at 45 mph and the lube system fails (pump shaft shears, major oil leak, etc.) how would the driver know so he can immediately stop and turn off the engine ?
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Old 05-30-2020, 07:02 AM   #14
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Default Re: Oil Pressure - OK

Thanks for the affords answers.

The reason for my question about the final pressure of the oil pump is as follows: I have switched to an oil filter. Since I drive SAE 50 blocks the fine micronic paper filter the flow when the oil is still cold at 12 C.

That's why I chose a very large filter bowl that has a bypass valve. That opens at 18 PSI. (My pressure gauge scale ends at 10 PSI.)

Therefore I am interested in the pressure increase of the pump PSI/RPM to estimate how well it works with the bypass.


Mulletwagon: You can use a pressure switch. If the oil pressure gets at zero, a warning light switched on.
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Old 05-30-2020, 11:27 PM   #15
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Default Re: Oil Pressure - OK

Quote:
Originally Posted by Werner View Post
Thanks for the affords answers.

The reason for my question about the final pressure of the oil pump is as follows: I have switched to an oil filter. Since I drive SAE 50 blocks the fine micronic paper filter the flow when the oil is still cold at 12C.
I guess the question should be; why are you using such heavy oil at ~50F?
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Old 05-31-2020, 01:35 PM   #16
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Default Re: Oil Pressure - OK

Just drive it,a lot more important things to worry about.
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Old 05-31-2020, 01:58 PM   #17
Charlie Stephens
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Default Re: Oil Pressure - OK

Quote:
Originally Posted by Jack Shaft View Post
Vw oil pressure switch 7.5 lbs

The model a engine uses a pump, splash and gravity fed lubrication system. The pump lifts oil into the valve gallery (behind the valve cover,behind the carburetor) the gallery had dams that trap the oil which splash lubricates the valve lifters springs and guides. The oil also flows from the pools down to the main bearings and cam bores through tubes and drilled ports to the cam.Oil pump flow is high enough to keep these pools constantly full of oil,the excess drains back through the drain tube and a hole knocked in the block above the timing gear lubricating the gear teeth,this oil then drains into the dipper tray where the rod bearings are fed by dipper cups that pass through the dipper tray oil, the rods passing through the dipper tray creates the monsoon effect of oil spray present when operating

The ford system used in the model a is very effective,you do not need pressure to create the hydrodynamic principle to lift and support the crankshaft on film of oil,constant flow is sufficient to protect the bearings.Dipper rod lubrication is good to 4k rpm,any faster and the cup moves too quickly to pick up oil.

An oil pressure gauge is a novelty,when cold starting an engine you can hear the dry valve train,it takes about 15 to 30 seconds to fill the valve galley..you never want to fire up and drive an a engine,give the pump a chance to fill the valve galley before you put a load on the engine.basically let it warm up a bit at 500 rpm or so
This one closes at 4 PSI. https://www.issprogauges.com/Heavy-D...ss-r4006-4.htm It is a candidate to use with the "dual-temp" gauge on my '32. They have custom ones available but I didn't check them since it is Sunday.

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Old 06-01-2020, 12:23 PM   #18
Werner
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Default Re: Oil Pressure - OK

Rocket 1,
you're right! Sometimes I bite into small things that are unnecessarily.

Ruth,
here on the edge of the North Eifel the nights are still very cold in the transition season. When the engine starts, the temperature may be 10 C. During the day over 25 C. Because here are steep valleys the engine has to pull very long upway and the water comes nearly to the boiling point.

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