Re: Oil Pressure Concern

[Jerry/MT]

Is this for a cold engine or is the engine at operating temperature? What is the spec for the 8N?(25-30 psi???)
Is the oil pressure relief valve adjustable on the 8N? What did the mains and rods Plastigauge at?
The main things affecting the oil pressure are, bearing clearnace, oil viscosity and oil temperature, relief valve spring tension & relief passage area, oil pump clearances, and engine speed.
In theory, the relief valve should control the pressure on a newly rebuilt engine to the relief pressure setting until the wear in the main bearings becomes excessive and the relief valve goes closed. After that, the bearing clearances are controlling the pressure.
On my TO-30 with about 500 hrs on a remanufactured engine, my oil pressure is constant at 27 psi hot or cold, idle or max rpm againsnst a spec of 25-20 psi so my relief valves is still controlling the pressure.

If there is a way to adjust the pressure on your relief valve you should find out how that"s done. JMOR or Dell(WA) or Bruce(VA) might be able to help you there. If there is no spring tension adjustment, then you"ll need to find out what the spec is for pressure and try some softer spring(s).

 

[8N457568Guy]

First thanks for the answer. Background, this was a post from a few weeks ago. I reported back after following the good advice I recieved but the thread "split."

Here is a little more background. "52 side mount 6 volt. I purchased it in August. Lot"s of "field engineered" solution on it including a rats nest of wires, bailing wire in place of governor control, and other fun things.

The oil relif valve isn"t adjustable. The spring I removed was stretched to twice the length of the replacement I installed.

The oil pressure has been high since it arrived.

Jim Smith says on his excellent website that pressure should be 25 - 45 cold and not below 20 warm.

Before I changed guages, it indicated mid to high 70"s cold and 65 warm.

Running 30 weight.

 

[souNdguy]

That's too high... 70's excessive... even on a fresh enigne with new oil pump, new mains and cam bearing inserts.. I don't think you should see more than 55psi.. change the oil filter.. I know it's near last.. but check anyway.. it's cheap..

soundguy

 

[Anonymous-0]

Try some 5w30.What's the temp in your area?

 

[8N457568Guy]

I changed the oil and filter last weekend. I"m pretty frustrated at this point.

 

[gahorN]

I disagree that 70 psi is excessive or too high. It is harmless. It means you have tight clearances in bearings and oil pump and it will be self-correcting as the engine wears.

There is absolutely nothing that will be injured by 70 psi pressures in the lubrication system, however you might wish to confirm that the oil-return line from the "T" to the oil-filter , and from the filter to the crankcase, is open and flowing freely.

 

[Den N Ms]

Guy, you say that you replaced the relief spring?It could be the replacement is too stiff.Compare the compression stiffness with the old one even tho its has been stretched out.It may be to stout and not relief the oil pressure easy enough.Maybe its another made in the land of almost right part?

 

[TheOldHokie]

(quoted from post at 14:25:31 10/18/09)
I disagree that 70 psi is excessive or too high. It is harmless. It means you have tight clearances in bearings and oil pump and it will be self-correcting as the engine wears.

There is absolutely nothing that will be injured by 70 psi pressures in the lubrication system, however you might wish to confirm that the oil-return line from the "T" to the oil-filter , and from the filter to the crankcase, is open and flowing freely.

So Ford and every other manufacturer in the universe spends money to install an over-pressure relief valve in the lubrication system for no good reason??? One side-effect of operation for extended periods with excessive oil pressure is eroded bearings.

TOH

 

[gahorN]

(quoted from post at 17:11:11 10/18/09)

(quoted from post at 14:25:31 10/18/09)
I disagree that 70 psi is excessive or too high. It is harmless. It means you have tight clearances in bearings and oil pump and it will be self-correcting as the engine wears.

There is absolutely nothing that will be injured by 70 psi pressures in the lubrication system, however you might wish to confirm that the oil-return line from the "T" to the oil-filter , and from the filter to the crankcase, is open and flowing freely.

So Ford and every other manufacturer in the universe spends money to install an over-pressure relief valve in the lubrication system for no good reason??? One side-effect of operation for extended periods with excessive oil pressure is eroded bearings.

TOH

TOH, that's not what I'm saying. What I am saying is: 70 psi ain't harmful, and his pressure-relief valve IS OPERATING just fine with the original spring and plunger. (If it wasn't then the pressure would shoot way over 100 psi ...which WOULD disturb me. Many, many, engine mfr's commonly run oil pressures at 60-80 psi or so and allow pressures to increase to 100 before raising alarms. Oil pressures below 100 will not cause erosion.
I DO have a curiosity about his pressure, and I suspect he has a restriction in his oil filter/return system.

 

[TheOldHokie]

(quoted from post at 18:41:15 10/18/09)

(quoted from post at 17:11:11 10/18/09)

(quoted from post at 14:25:31 10/18/09)
I disagree that 70 psi is excessive or too high. It is harmless. It means you have tight clearances in bearings and oil pump and it will be self-correcting as the engine wears.

There is absolutely nothing that will be injured by 70 psi pressures in the lubrication system, however you might wish to confirm that the oil-return line from the "T" to the oil-filter , and from the filter to the crankcase, is open and flowing freely.

So Ford and every other manufacturer in the universe spends money to install an over-pressure relief valve in the lubrication system for no good reason??? One side-effect of operation for extended periods with excessive oil pressure is eroded bearings.

TOH

TOH, that's not what I'm saying. What I am saying is: 70 psi ain't harmful, and his pressure-relief valve IS OPERATING just fine with the original spring and plunger. (If it wasn't then the pressure would shoot way over 100 psi ...which WOULD disturb me. Many, many, engine mfr's commonly run oil pressures at 60-80 psi or so and allow pressures to increase to 100 before raising alarms. Oil pressures below 100 will not cause erosion.
I DO have a curiosity about his pressure, and I suspect he has a restriction in his oil filter/return system.

I know of no automobile that runs anything even close to 100 PSI even cold. Based simply on the fact that the original N gauges were 0-50 PSI I have to believe the oil pressure relief valve is intended to regulate pressure at or below 50 PSI. If there's a blockage causing the elevated pressure it's likely in the oil pressure relief valve itself - it dumps directly back into the sump - not through the filter - and is located in-line between the pump output and the bearings. Personally I'm suspicious of the accuracy of the 70 PSI number.

TOH

 

[souNdguy]

I disagree. something is amiss.

when that machine left the factory new.. it's oil pressure relief was set right around 45psi.. thus he shouldn't be seeing mor ethan about 50 max, on a tight cold engine.. the rest of the oil should be dumping. it's running nearly 25 psi past relief pressure... most N don't even see 25 with a jimmied spring.

IMHO.. it left the factory with better tolerances and tighter clearances than it is likely rebuilt now considering without custom machine work on to insert bushing or shells for the cam where it rides bare in the block, then there will be open tolerances past what was new.

soundguy

 

[gahorN]

(quoted from post at 19:25:57 10/18/09) I know of no automobile that runs anything even close to 100 PSI even cold. Based simply on the fact that the original N gauges were 0-50 PSI I have to believe the oil pressure relief valve is intended to regulate pressure at or below 50 PSI. If there's a blockage causing the elevated pressure it's likely in the oil pressure relief valve itself - it dumps directly back into the sump - not through the filter - and is located in-line between the pump output and the bearings. Personally I'm suspicious of the accuracy of the 70 PSI number.

TOH

Well...most automobiles have idiot lights so it's unlikely you actually have much info as to what any of them are actually running as far as pressure goes.
Here's a related subject: I have a Continental aircraft engine which the mfr specifies should run 30-45 psi. Mine indicates 60 psi. I got worried and talked to the design engineers at Continental and they were much amused at my concerns, and gave me quite an education about reciprocating engine lubrication systems.
Many telephone calls and consultation with them resulted in the bottom line: Up to 100 psi is OK in reciprocating engines that do not have hydraulic lifters. Up to 75 is fine with hydraulic lifters.
Chase that high oil pressure if you want to, but most folks would be jealous of that kind of good pressure.
I think he should make certain there's no down-stream blockage (such as that oil filter circuit) and enjoy the pressure.
If the rest of you guys want to feed his paranoia and waste his time and money...then keep on.
Your mileage may vary, it's only my opinion.

 

[TheOldHokie]

(quoted from post at 00:00:58 10/19/09)

(quoted from post at 19:25:57 10/18/09) I know of no automobile that runs anything even close to 100 PSI even cold.

TOH

Well...most automobiles have idiot lights so it's unlikely you actually have much info as to what any of them are actually running as far as pressure goes.
Here's a related subject: I have a Continental aircraft engine which the mfr specifies should run 30-45 psi. Mine indicates 60 psi. I got worried and talked to the design engineers at Continental and they were much amused at my concerns, and gave me quite an education about reciprocating engine lubrication systems.

I explicitly said "automobile" engine - I have no experience with aircraft engines and I fail to see any real relevance of your Continental aircraft motor to a discussion of oil pressure in a flathead Ford. Most every [u:4849792397][b:4849792397]automobile[/b:4849792397][/u:4849792397] I have ever owned has had an oil pressure gauge and they were regulated no higher than 60 PSI. My hi-tech German built Caddies are regulated at ~75 PSI and surprised the heck out of me when I first aquired them. But once warmed up they carry 60 PSI @ 3500 RPM, 22+ PSI @ 600 idle. At 2000 RPM it's closer to 40 PSI.

I have no real idea what if any damage that sort of elevated pressure might cause over time in an N - perhaps none. But something is WRONG in that motor - either there is an obstruction in the lubrication system or the gauge is giving an incorrect reading. If it were my motor I'd want to find and identify the problem for fear that it's indicative of something serious that may cause issues down the line. I do not consider that paranoia - just plain old prudence.

TOH

 

[gahorN]

(quoted from post at 08:24:32 10/19/09)
I explicitly said "automobile" engine - I have no experience with aircraft engines and I fail to see any real relevance of your Continental aircraft motor to a discussion of oil pressure in a flathead Ford. Most every [u:53e70627ec][b:53e70627ec]automobile[/b:53e70627ec][/u:53e70627ec] I have ever owned has had an oil pressure gauge and they were regulated no higher than 60 PSI. My hi-tech German built Caddies are regulated at ~75 PSI and surprised the heck out of me when I first aquired them. But once warmed up they carry 60 PSI @ 3500 RPM, 22+ PSI @ 600 idle. At 2000 RPM it's closer to 40 PSI.

I have no real idea what if any damage that sort of elevated pressure might cause over time in an N - perhaps none. But something is WRONG in that motor - either there is an obstruction in the lubrication system or the gauge is giving an incorrect reading. If it were my motor I'd want to find and identify the problem for fear that it's indicative of something serious that may cause issues down the line. I do not consider that paranoia - just plain old prudence.

TOH

I am only participating in this discussion as a FRIEND and do not mean to imply that anyone here is any better/smarter/dumber than anyone else. I hope I haven't offended anyone's sensibilities....
Now... you said we're talking about AUTOMOBILE engnes....and we are not. We are talking about ENGINES in GENERAL....and TRACTOR engines specifically. The airplane engine I was discussing is of the same vintage as this tractor engine we are discussing and is about the same sophistication.
I do not believe the "higher" oil pressure being experienced is indicative of any serious problem that requires any extensive or expensive investigation. Firstly...because he's already looked at the relief valve and determined it DOES work! This will preclude any over-pressure damage.

The oil pressure sensing is taken DOWNSTREAM of the pressure relief...and UPSTREAM of the oil filter. Imagine if the oil filter cannister were blocked...or the line leading to the cannister were blocked...what that might mean to indicated oil pressure....and what that might mean to the supply of return-oil to the engine. THAT is where I believe it is possible to easily determine problems that COULD be hurtful to the engine.

I believe the pressure relief valve focus is a red herring.

 

[TheOldHokie]

(quoted from post at 11:15:40 10/19/09)
The oil pressure sensing is taken DOWNSTREAM of the pressure relief...and UPSTREAM of the oil filter. Imagine if the oil filter cannister were blocked...or the line leading to the cannister were blocked...what that might mean to indicated oil pressure....and what that might mean to the supply of return-oil to the engine. THAT is where I believe it is possible to easily determine problems that COULD be hurtful to the engine.

I believe the pressure relief valve focus is a red herring.

I think you need to think about that some more. From my rudimentary understanding of hydraulics if the pressure at the gauge were higher than at the relief valve oil would flow backwards through the system. Here's what I believe:

If you remove the oil line fitting on the back of the block and install a screw in dead ended pressure gauge the relief valve will open at its cracking pressure and dump the excess oil flow (if any) from the pump back into the sump via the front cover. You will have no filtering, no governor lube, and main/rod/camshaft bearing oil pressure less than or equal to the cracking pressure of the valve.

That is what the valve is there for - it works just like the over pressure relief valve on the hydraulic pump and is positioned in a very similar location in the system.

TOH