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roy53

high oil pressure

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Firstly my release valve is not stuck. When revs go high above 4000 the needle goes of the gauge beyond 100 lbs to the extent that it blew the rubber ring on the top of the oil filter out.

 

Any ideas how to bring it down ?????

 

Roy

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Firstly my release valve is not stuck. When revs go high above 4000 the needle goes of the gauge beyond 100 lbs to the extent that it blew the rubber ring on the top of the oil filter out.

 

Any ideas how to bring it down ?????

 

Roy

Have you got the proper spring fitted to the pressure release valve?

 

Bruce.

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Pressure like that has to be a restriction if its appeared off the cuff.

Presumably as you are saying this now you havnt just fitted a new spring but even so it only gives a little bit more.

First suspect would be oil filter. What type do you have?

I run an oil cooler and with new 20-50w oil at high revs from cold it gives high pressure but never off the gauge.

Dont know if its relevant but what about the breather?

Edited by Rem18

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A bit more detail might help.

Newly rebuilt engine?

Anything done to it recently?

"Rubber ring "? Is this a OE Filter or do you have a spin on?

Oil cooler?

John

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I had a 6 in once that was like that so much to the extent that revved when cold it blew the oil cooler apart, turned out someone had fitted washers under the relief valve spring.

Stuart.

post-3753-0-41940600-1526053198_thumb.jpg

post-3753-0-55383900-1526053228_thumb.jpg

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Hi Roy,

How do you know your relieve valve is bot stuck when installed? It may move fine when removed from the egine bt Mine has a very tight diametrical clearance, so I wondered if this results in sticking in some cases.

Waldi

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ok so this is a new race engine done 3 races.It has an oil cooler and spin on filter MAHLE . It still reads this when hot. I will be trying the valve from my 5 tomorrow ,this reads high when started but drops when hot to normal by which i mean 50 lbs. Will also try spacer washer on the external part of the valve.

 

Waldi no i have no idea.

 

John now you know who left the long oil slick at silverstone on saturday.

 

Rem 30mm breathers from rocker cover and from the engine block.

 

ROY

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I changed a relief valve spring because it was short according to the BB. The new spring took the needle off the gauge when cold so I went back to the original, shorter spring.

 

I assume a previous owner fitted the shorter spring for a reason lost in the mists of time.

 

My oil pressures are good with the shorter spring so I'm leaving well alone.

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Thank you, Roy! That slick gave everyone some moments!

 

Oil thermostat wrong way around? I did the same thing on the road, when I first fitted an oil cooler, blew the oil lines off the connectors but that happens as soon as the oil temp gets up, which would have happened previously.

 

John

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Pretty much has to be the relief valve. Even if it appears to be doing something, it is obviously not doing enough.

 

The issue is that the oil pump is a positive displacement device and the amount it pumps is directly proportional to it's spindle speed. Double the revs, double the flow. Ok, it's driven at cam speed rather than engine speed, but even so.... you get a tenfold increase in flow between 300 rpm and 3000 rpm. The design displacement is set by choosing a big enough pump to provide just enough flow at idle, with a design margin. But the amount of oil needed by the engine does not rise all that much with rpm, certainly nothing like 10-fold. So you absolutely have to have a relief valve to dump the considerable excess flow back into the sump - and there is one, right after the pump. At 4000 rpm the pump will be doing 2000rpm (3/4 of it's normal max) and probably 60% of it's output will be going straight back to the sump via the relief valve.

 

The Triumph relief valve is a somewhat crude device and appears to be intentionally designed to give a rising rate - which is to say that it is intentionally slightly undersized so that the relieving pressure rises with the flow rate. A perfectly sensible thing to do in the context of an engine oil supply, but does mean that quite small changes to the spring rate (even skinny washers added) can have a disproportionately large effect at higher rpms.

 

There are quite a few variants of the springs out there, at least one of which becomes coil- bound before the plunger is fully returned, which could have this kind of effect. I've also seen a relief housing (on my old Herald 1200) which had compacted sludge (a chunk of random debris/swarf would have the same effect) in the plunger drilling that prevented it fully retracting and gave more than 100psi at >3000rpm when cold even though the engine was well worn. Suspect that it had never been over 2000rpm in it's life before it came to me.

 

Bottom line - it's the relief valve, you just have to work out why.

 

Nick

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Nice explanation Nick. Makes me want to to take it out and clean it now. :)

Edited by Rem18

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Thanks both John and Nick for input.

John i do not have an oil thermostat.

Nick thanks for your explanation .

Yesterday i tried the valve from my standard 5 with no change,interesting that the spring lengths were about 10mm different so tried spacing washers between the valve and block.To big and lost pressure so reduced sizes which lowered it but still at high revs 80 but not off the gauge.Trying not to lose pressure at low revs was the challenge.

Will order a complete valve from MOSS but they do not list different length springs so will see what turns up.

 

Thanks again Nick nice information and agree valve favourite,the engine block was thoroughly cleaned before build.

 

ROY

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Hi Roy,

 

This is really strange - swapping the valve and spring out to make a difference - especially with 10mm difference in length!! Is the oil pressure take off in the usual place - ie T'd off the usual oil pressure switch location under the distributor?

 

Nick

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80 psi with a cold engine is pretty normal. What's the problem pressure at low revs?

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