Shiming the oil pump pressure relief spring

BobR35

BobR35

Senior Member
Since my intake is off I'm wondering if and what your ideas or experiences are in order to increase the oil pressure by shiming the regulator spring on my '35 stock motor with lo pressure after warmed up. Florida weather, 5lbs or less at idle hot.
thanks
 
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Re: Shiming the oil pump pressure regulatory

My guess is the engine is worn out. That won’t rebuild it. Probably not help at all there’s other factors why you have low oil pressure.
 
Re: Shiming the oil pump pressure regulatory

I think Tony has the correct answer. How much oil pressure does it have running down the road ?
 
Re: Shiming the oil pump pressure regulatory

The spring your are referring to is actually called a "relief spring". It's function is to allow excess pressure from the oil pump to "blow off", preventing an over-pressure situation. As such, there is no way to manipulate it to increase oil pressure.
 
Re: Shiming the oil pump pressure regulatory

tubman said:
The spring your are referring to is actually called a "relief spring". It's function is to allow excess pressure from the oil pump to "blow off", preventing an over-pressure situation. As such, there is no way to manipulate it to increase oil pressure.
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Understand that. But do they go bad and allow too much oil to pass thereby lowering the pressure?
 
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It sounds like the bottom end may have some wear, has it always had this problem or is it a new thing? I had this happen on 38 Lincoln when I added the old style oil filter. I wasn't aware the there should have been a metering fitting(AKA restrictor) in line. if this has been the norm for a long while I would run 20 50 and see if it helps.One last thing would be to put a temporary mechanical oil pressure gauge on it to verify what your stock gauge is telling you. Tim
 
Re: Shiming the oil pump pressure regulatory

BobR35 said:
Understand that. But do they go bad and allow too much oil to pass thereby lowering the pressure?
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Generally no...but it sure won't hurt to inspect the spring and valve while you have the intake off. If the seating areas look good and the spring is in one piece and has decent tension it won't improve pressure to shim it in your case. However, it won't hurt anything either.

The 5 lbs at warm idle and 10 lbs at speed is a bit odd. Usually an engine with 10 lbs at speed will idle at zero. The gauge may be suspect if the relief valve and spring are ok.



Terry
 
Re: Shiming the oil pump pressure regulatory

cadillac512 said:
Generally no...but it sure won't hurt to inspect the spring and valve while you have the intake off. If the seating areas look good and the spring is in one piece and has decent tension it won't improve pressure to shim it in your case. However, it won't hurt anything either.

The 5 lbs at warm idle and 10 lbs at speed is a bit odd. Usually an engine with 10 lbs at speed will idle at zero. The gauge may be suspect if the relief valve and spring are ok.



Terry
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You know your stuff! It had "0" at idle before the teardown, I was being optomistic. I took a look at the oil relief valve and spring today prior to putting the intake back on and it was in good physical condition in appearance. I did put a 1/4" shim at the top of the spring insert since I was there and figured it couldn't hurt anything. I completed the intake installation and went for a drive for about 25 minutes and included traffic, stops, steady 45mph speeds and long idles. I noticed an improvement in the oil pressure at all areas, up about 10lbs at speed and 5 at idle when hot. It was 87* and I'm impressed right now with the difference. I'll be driving to a show tomorrow, 30 miles one way and will get a better look at the long term affect. I also think that after blocking the heat rise from recycling into the carb that it is running cooler and the engine is running smoother/better. I do have mechanical guages, one temp for each head (L&R), and one for the oil. I'm anxious to drive more tomorrow and get more data and I'll share that info back here. Thanks again for your input, much appreciated.
 
pistonbroke said:
It sounds like the bottom end may have some wear, has it always had this problem or is it a new thing? I had this happen on 38 Lincoln when I added the old style oil filter. I wasn't aware the there should have been a metering fitting(AKA restrictor) in line. if this has been the norm for a long while I would run 20 50 and see if it helps.One last thing would be to put a temporary mechanical oil pressure gauge on it to verify what your stock gauge is telling you. Tim
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Thanks Tim, I am running 20/50 oil and have a mechanical guage, this issue has been there for a while.
 
here are pictures of the spring
 

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I've always wondered about flathead filters. Modern clean roads and all. Change oil at 2000 miles or so. You should be good. Newc
 
Newc said:
I've always wondered about flathead filters. Modern clean roads and all. Change oil at 2000 miles or so. You should be good. Newc
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For sure, I drive a lot so I drain it around 1000 mi. It's quick and easy.
 
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