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Discussion Starter #1
Rather than continue to highjack another thread I though I'd post up a new thread with a question I have

So I have this early 50's L with a low pressure oil pump, I have converted over to a spin-on oil filter along with a Gravely OEM low pressure oil gauge. At cold idle the needle is pegged, after an hour of good use there is little to no indicated oil pressure, however there is a very good stream of oil coming from the relief valve, as the engine cools the pressure will rise 1-3 psi indicated. FLDon recommended adjusting the relief valve to try and get 5 [email protected] idle, today I tried, however I can't seem to adjust the pressure.....anyone out there with knowledge on how to properly adjust oil pressure on a low pressure oil system please chime in.


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FWIW, I just converted a 49 L to a spin-on filter and I added a 0-30 psi pressure gauge to it too. Oil pressure showed about 8 psi at higher RPM on the first start with fresh SAE40 in the crankcase. I tightened the adjustment on the relief valve up as tight as I dared, and I still couldn't get more than about 10 psi at RPM. Plenty of oil coming through the valve too.

I disassembled the relief valve and everything looked okay there. I found a couple of lockwashers of the correct size to serve as shims to increase the spring pressure. Oil pressure is now just under 15 psi cold, and still a good healthy stream of oil at the filler. I guess that spring is weak. If it ever quits raining here, I'll go mow some and get it up to operating temp, and see what the oil pressure is then. If it drops much below 5 psi, I may add another shim or two to the valve.
 

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Before this thread gets too far, I guess that needs to be cleared up.

The low pressure system, or low volume system, is the partial-oil-filter-bypass system. There is a tee in the line from the oil pump. The engine gets unfiltered oil directly from the the oil pump, and any excess gets pushed through the filter, and out the filler neck.

That's the way my 49 was plumbed, and I have not changed it.
 

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Discussion Starter #5
Did you re-plumb the oil lines or just add the filter the same way the canister was plumbed?

The oil lines are plumbed same as old filter and as Gravely instructs.


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Discussion Starter #6
Just to clear things up, the oil lines are plumbed as Gravely instructs when upgrading to the spin-on oil filter. The oil pump is still plumbed as a bypass system. No I did not remove the T fitting on the case....oil pressure is week at idle, just thought I could get a few more PSI buy adjusting the pressure relief. I'll probably try stretching the spring a bit or shimming it.


Really in the end the engine is just old and probably needs a lower end rebuild. ImageUploadedByMyTractorForum Free App1404094730.125886.jpg


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The fitting on the oil relief valve is a 1/8 NPT. If that valve was intended to be adjustable, why would they use a tapered thread on it? You can adjust the pressure some by varying how tight that fitting is, but I wonder if it was actually intended to be that way. You can only tighten it so much before you risk damaging it. If it is too loose, it will leak. I doubt that shims were intended either, but at least that allows you to get the desired oil pressure without overtightening or undertightening that NPT fitting.
 

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Discussion Starter #8
The fitting on the oil relief valve is a 1/8 NPT. If that valve was intended to be adjustable, why would they use a tapered thread on it? You can adjust the pressure some by varying how tight that fitting is, but I wonder if it was actually intended to be that way. You can only tighten it so much before you risk damaging it. If it is too loose, it will leak. I doubt that shims were intended either, but at least that allows you to get the desired oil pressure without overtightening or undertightening that NPT fitting.

I completely agree with your thoughts, while the later high pressure system relief is intended for adjustment I don't feel the early relief is. As you mentioned the 1/8 fitting is tapered, this will only allow for a very small adjustment if any at all.


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Just stirring it up some more,

For those who have never seen the internals of a Low Volume relief valve.

Low volume.1.jpg Low volume 2.jpg

If you wanted to increase oil pressure to the engine, stretch the spring a tad or, back the spring with some itty bitty washers in the spring bore, but that would starve oil going to the forward/reverse planetary gears.

If you wanted to increase oil pressure to the F/R planetary, then simply back the smaller 1/8 pipe fitting out some and use a Permatex thread sealer.

Roger,
 

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Discussion Starter #10
Well.....the pressure relief valve from my 49' L and early 50's L do not have the steel ball but a plunger with a hole, both engines for sure have a low pressure oil pumps.


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Discussion Starter #11
This is what I found inside of my pressure relief valve, as I mentioned the 48' L has the exact same valve internals, no steel ball.

ImageUploadedByMyTractorForum Free App1404171261.076830.jpg ImageUploadedByMyTractorForum Free App1404171281.283950.jpg ImageUploadedByMyTractorForum Free App1404171296.614404.jpg


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That's the same type valve as mine.

There is a hole down the middle of the plunger. Regardless of how restrictive the spring/plunger is, some oil will pass through that hole. It's a pretty good little stream... I'd say it's plenty for the F/R planetary gear.
 

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Discussion Starter #13
Just stirring it up some more,



For those who have never seen the internals of a Low Volume relief valve.



View attachment 871313 View attachment 871321



If you wanted to increase oil pressure to the engine, stretch the spring a tad or, back the spring with some itty bitty washers in the spring bore, but that would starve oil going to the forward/reverse planetary gears.



If you wanted to increase oil pressure to the F/R planetary, then simply back the smaller 1/8 pipe fitting out some and use a Permatex thread sealer.



Roger,

Roger could the pressure relief valve you referenced in this post be a late version of the low pressure relief valve?

Too me the low pressure relief valve on the early L's is not designed to be adjustable, at least not like the later relief valves as installed on tractors with high pressure oil pumps. The two relief valves I've taken apart are designed to always allow some oil to pass, I assume this was done always ensure oil gets to the forward planetary gears.


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The one in my photos was from a mongrel tractor and was probably a late low pressure relief valve.

Does the plunger in the above photos have a small hole drilled through the center?

My 58 LI had a low volume oil system. I think Gravely changed to high volume in 1959 or 1960.

Roger,
 

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Discussion Starter #15
The one in my photos was from a mongrel tractor and was probably a late low pressure relief valve.



Does the plunger in the above photos have a small hole drilled through the center?



My 58 LI had a low volume oil system. I think Gravely changed to high volume in 1959 or 1960.



Roger,

Roger,
Yes there is a hole through the middle of the plunger, it's almost like a fail safe to always keep the forward gears lubricated


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The valve only restricts the maximum oil pressure. It's closed on any pressure below that. (except for the stream through the orifice in the plunger.)

The shims I'm adding to the spring are .050 inch thick. Each one added about 3 psi to the oil pressure.

The maximum oil pressure I could get was 20 psi, at operating rpm with a cold engine. That was three shims. I decided to set the maximum oil pressure at 15 psi.

With a cold engine, the oil pressure stays at about 15 psi at operating rpm, and around 8 psi at idle.
With a hot engine, the oil pressure stays at about 10 psi at operating rpm, and around 4-5 psi at idle.

I can live with that.
 

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Discussion Starter #17
The valve only restricts the maximum oil pressure. It's closed on any pressure below that. (except for the stream through the orifice in the plunger.)



The shims I'm adding to the spring are .050 inch thick. Each one added about 3 psi to the oil pressure.



The maximum oil pressure I could get was 20 psi, at operating rpm with a cold engine. That was three shims. I decided to set the maximum oil pressure at 15 psi.



With a cold engine, the oil pressure stays at about 15 psi at operating rpm, and around 8 psi at idle.

With a hot engine, the oil pressure stays at about 10 psi at operating rpm, and around 4-5 psi at idle.



I can live with that.

Wow, good results, guess I'll be making a trip to Ace hardware


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...My 58 LI had a low volume oil system. I think Gravely changed to high volume in 1959 or 1960.

Roger,
I have a '57 LI that has the high pressure/volume lubrication system... factory, not a conversion.

Seems that the one consistent thing about the old L's is that they are not consistent.
 

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I have a '57 LI that has the high pressure/volume lubrication system... factory, not a conversion.

Seems that the one consistent thing about the old L's is that they are not consistent.


Or you may have the original air shroud over newer cases.

You can build a new tractor under an old serial number and have a hard time identifying what is new and what is old.

Roger,
 

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Or you may have the original air shroud over newer cases.

You can build a new tractor under an old serial number and have a hard time identifying what is new and what is old.

Roger,
+1

I don't believe any '57s could've had the high-volume system from the factory. That didn't appear until more than halfway through '58. Fan shrouds got swapped all the time (and still do) due to cracking.
 
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