Adjusting Oil Pressure Relief Valve

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Stephen Hill

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Oct 28, 2009
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The oil pressure relief valve on my 1972 Combat is a little ratty. I have a few freshly plated components that I want to use to build/swap in a nicer unit. I would like to test the new valve off the bike and make sure it is operating within specs.
I understand that some folks just install 1 or 2 shims, and call it good, and some folks just use enough shims so that it rattles a bit, etc.
I would prefer to pressurize it and measure actual blowoff. Any cheap and cheerful ways of doing this?
I would like to avoid spending 10 hours making up a bunch of weirdo adapters with archaic threads, to perform a test that will last 6 seconds or less. Any ideas?
 
I put a Norton Holland oil pressure gauge on my bike and my relief valve with no shims limits to about 45 psi cold.
 
The gauge is very well constructed with a braided wire shielded hose.
No worry of burst hose with this one.
I like to know what the oil pressure is.
And the volts too so have installed a cheap digital gauge between the
handbars.
Dennis
 
Stephen Hill said:
The oil pressure relief valve on my 1972 Combat is a little ratty. I have a few freshly plated components that I want to use to build/swap in a nicer unit. I would like to test the new valve off the bike and make sure it is operating within specs.
I understand that some folks just install 1 or 2 shims, and call it good, and some folks just use enough shims so that it rattles a bit, etc.
I would prefer to pressurize it and measure actual blowoff. Any cheap and cheerful ways of doing this?
I would like to avoid spending 10 hours making up a bunch of weirdo adapters with archaic threads, to perform a test that will last 6 seconds or less. Any ideas?
Click to expand...
Given how old your current one is and how critical the application, why not do your bike a favour and get one of these:

Norton twin Stainless steel pressure release valve 1960-75 | SRM Classic Bikes

shop.srmclassicbikes.com shop.srmclassicbikes.com

It's already been tested and set.
 
Stephen Hill said:
How do you know it is set correctly? I would want to test it. In which case I would just build a nice one from my parts stash.
Click to expand...
Just because it's English doesn't mean you can't trust it - I know where you're coming from though!
Then again, I suppose you are from Canada!
;) ;)
 
Last edited:
I use the SRM pressure relief valves and have an oil pressure gauge attached to my ride. It pops at about 60 PSI on a cold engine and runs at about 45 PSI when the engine is warmed up @ about 3500-4000 RPM. I have been very pleased with these except with the fiber washers that came with it as they always wept a little oil and occasionally would loosen off. The copper washers are the way to go. I think these have now been replaced with copper washers. They are S/S as they don't rust like the originals did as time goes on.
 
CanukNortonNut said:
I use the SRM pressure relief valves and have an oil pressure gauge attached to my ride. It pops at about 60 PSI on a cold engine and runs at about 45 PSI when the engine is warmed up @ about 3500-4000 RPM. I have been very pleased with these except with the fiber washers that came with it as they always wept a little oil and occasionally would loosen off. The copper washers are the way to go. I think these have now been replaced with copper washers. They are S/S as they don't rust like the originals did as time goes on.
Click to expand...
The interesting thing is the OPRV's only job is to bleed off excess pressure. So, it sounds like it's doing that with cold oil and doing nothing once warmed up. Makes me think the pump cannot make 60psi with hot oil (might be pump or oil leaving the big ends or rockers more easily).
 
I once made a test setup when I wanted to test several.
Fill the metal tube with oil and increase the air pressure till the valve blows.
Crude and messy (place it in a bucket for testing..), but it worked fine:

Adjusting Oil Pressure Relief Valve
Pic. is just for illustration, not exactly how I did it.

Adjusting Oil Pressure Relief Valve
 
I had a rudimentary bench test set-up for PRV a while back. PRV mounted in spare timing cover. Air compressor to input port. Pressure gauge on rocker feed.
There was always some leakage thru the PRV (roughly 20%). I measured pressure coming from the rocker feed line hole with given input air pressure, as measured on compressor gauge. Not sure how valid this is with air rather than oil, but shows functionality at least.

Adjusting Oil Pressure Relief Valve
 

Mr. Mike's OPRV

This alteration to the oil pressure control system on A65/50 motors will greatly improve your oil pressure both at idle speed and normal riding. The change gave me 18-20 psi at hot idle and 45-60 psi at cruising speeds. Here are the modifications: ⦁ Remove the existing OPRV from the c...
www.britbike.com www.britbike.com

As said in theese posts , most of the leakage is due to the thread of the OPRV in the timing cover and/or the piston , somewhere if I remenber well it has been said that the SS could be prone to galling .... just 9 pages to read , DMadigan is another Comstock ....
 

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