oil pressure release valve

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Please,
i would like to understand better what it works and what it needs and how it relates to oil pressure.
Thank you.
Piero
 
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Time Warp

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It is a shuttle valve (piston and spring) if there was a to high oil pressure (cold oil for instance) the excess oil pressure would overcome the piston spring, the piston would move rearward uncovering the orifice which goes to the inlet side of the oil pump (Into the feed from the oil tank.
I'm not sure a Commando would suffer from excess oil pressure having very narrow pressure side gears.

They can leak at the front thread reducing overall pressure apparently.
Oddly enough I got a mail out from SRM last night on the same subject and now have one on the way.


pr.jpg cvr.jpg
 
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Onder

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I have one they look fine but someone somewhere complained about rapid wear. Not enough miles on mine to say...
 

Time Warp

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I keep thinking I should get one of those. How is the quality?
It looks nicely made (externally) for under $100 to the door.

I would need to have a look inside and check the pressure setting at release to be sure but would be surprised if it sealed any better than the stock unit at the forward thread area.
It screws nicely but still has clearance even if slightly less that the OEM unit.

A test fit shows the passage in the timing cover is sitting about this position so there are not many threads in front of that 'hole.
(I could machine the timing cover pad to move the unit inward so the hole is in the channel but the front thread might still need some Wellseal)
I guess only a pressure test with the cover being used would show if there is leakage past the front thread, the OEM sealing/design is a little hit and miss as is .

rv.jpg


Maybe the shuttle body will need some moly paste from new and then periodically after that but in theory when it opens oil should get to that area . (Any wear will have to be an ongoing check)

I will get another one for the 750.
 

acadian

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Have been running the SRM unit for several years now, consistently levels off pressure at 50psi on cold start, I should probably get in there and check for leakage past the front threads though
 
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I have one they look fine but someone somewhere complained about rapid wear. Not enough miles on mine to say...
If this is the SRM valve with a stainless steel piston in a stainless steel bore, that is (at least theoretically) a bad choice of materials.
 

Fast Eddie

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I like the SRM valves, I like the quality, they seem to have good tight tolerances and I like their claims of testing each one.

I like them so much I’m running 3 of them.

Guess I should take one apart and check out the piston / bore wear topic...
 

maylar

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So, what are the symptoms, if any, of a worn out PRV? I've never removed mine let alone thought of replacing it.
 
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It looks nicely made (externally) for under $100 to the door.

I would need to have a look inside and check the pressure setting at release to be sure but would be surprised if it sealed any better than the stock unit at the forward thread area.
It screws nicely but still has clearance even if slightly less that the OEM unit.

A test fit shows the passage in the timing cover is sitting about this position so there are not many threads in front of that 'hole.
(I could machine the timing cover pad to move the unit inward so the hole is in the channel but the front thread might still need some Wellseal)
I guess only a pressure test with the cover being used would show if there is leakage past the front thread, the OEM sealing/design is a little hit and miss as is .

View attachment 20309

Maybe the shuttle body will need some moly paste from new and then periodically after that but in theory when it opens oil should get to that area . (Any wear will have to be an ongoing check)

I will get another one for the 750.













It looks nicely made (externally) for under $100 to the door.

I would need to have a look inside and check the pressure setting at release to be sure but would be surprised if it sealed any better than the stock unit at the forward thread area.
It screws nicely but still has clearance even if slightly less that the OEM unit.

A test fit shows the passage in the timing cover is sitting about this position so there are not many threads in front of that 'hole.
(I could machine the timing cover pad to move the unit inward so the hole is in the channel but the front thread might still need some Wellseal)
I guess only a pressure test with the cover being used would show if there is leakage past the front thread, the OEM sealing/design is a little hit and miss as is .

View attachment 20309

Maybe the shuttle body will need some moly paste from new and then periodically after that but in theory when it opens oil should get to that area . (Any wear will have to be an ongoing check)

I will get another one for the 750.

Have been running the SRM unit for several years now, consistently levels off pressure at 50psi on cold start, I should probably get in there and check for leakage past the front threads though
I tested one of the SRM units for a local club member to determine it's characteristics .

1. The threads are in fact tighter that any norton ORV I have tested. The reduced leakage past the timing cover threads is quite noticeable on the test rig flow gauge.
I did note a slight different location of the vent hole within the annular vent groove . However, I'd highly recommend to leave the threads of the cover alone.

2. Most noticeable was a different rate spring. The spring has finer wire but more turns and a preload that still makes the piston open the ports at similar pressure with one exception to the characteristics. The spring rate is lower the result being it open at the same pressure but as oil flow increases the port opening is quicker to open causing the vent pressure to not increase nearly as much as the OEM spring would do.

My oil test rig can run enough oil volume to make the Norton OPV not regulate but only mitigate the over pressure allowing the over pressure consistantly start at say ,50psi, and continue toward 75psi as the RPM's increase. With no OPV it would skyrocket to 150PSI.
The SRM OPV would much better respond to the increased flow and hold the pressure down much better.

TIME WARP:
It is a shuttle valve (piston and spring) if there was a to high oil pressure (cold oil for instance) the excess oil pressure would overcome the piston spring, the piston would move rearward uncovering the orifice which goes to the inlet side of the oil pump (Into the feed from the oil tank.

The exit passage for the vented oil is dependent on the NHT engine series . valid for 6 of NHT 26 years
 
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Time Warp

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The exit passage for the vented oil is dependent on the NHT engine series . valid for 6 of NHT 26 years

It vents to the oil inward passage on both my 850 and all the 20M3S cases I have, 20M3/ Mk111 850 I do not know (This is a Commando specific forum on the website so applied to that )
Its a moot point now as Peridon never returned to the thread he posted.
 
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It vents to the oil inward passage on both my 850 and all the 20M3S cases I have, 20M3/ Mk111 850 I do not know (This is a Commando specific forum on the website so applied to that )
Its a moot point now as Peridon never returned to the thread he posted.
Within all commando series they vent as you say except the MKIII which reverted to early style and vent inside the timing chest. There were a few pre MKIII mongrel commando engines also using MKIII type .
I think Piero is working on a 65 atlas but the OPV is the same for all NHT except a few mid/later 50 engines. 57 style
 
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