Rover v8 oil pressure relief valve - fixed!

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stu60
Posts: 106
Joined: Fri Jul 08, 2016 10:09 am
Location: Cheltenham

Rover v8 oil pressure relief valve - fixed!

Post by stu60 » Fri Feb 05, 2021 5:48 pm

Since major rebuild of engine with new top-hat linered block, bearings, pistons, camshaft, rockers, new oil pump gears in SD1 vitesses front cover etc i have experienced high oil pressure when the car is cold, if revved this could be 80+psi which didn't seem right. the car runs perfectly and with normal/new pressures when warm. Many people said what's your problem "a Rover with good oil pressure... you should be celebrating!". Just in case I have been not revving the car until the oil is warm but this is frustrating/impractical in the long run.

I assumed it must be the oil pressure relief valve sticking but after numerous checks that it was free moving i decided to replace the spring and the piston...just in case. The kit from Rimmers contained an 81mm spring but the one removed was only 71mm. Looking on some V8 forums they said the 81mm spring is the uprated high pressure one which was the last thing I wanted, so I refitted the existing 71mm spring BUT had same issues of high oil pressure when cold. i contacted Rimmers who suggested i fit the MGB V8 spring which is indeed shorter at c71mm. I couldn't find anyone who could tell me the correct length of the standard spring except on some other V8 forums they said the longer spring is definitely high presssure upgrade so my assumption was Rimmers sent by mistake the uprated spring they sell.

Before trying the MGBV8 shorter spring, I thought i would take another look...so removed the old 71mm spring to compare with the 81mm and ... the shorter (71mm) spring is actually the high pressure upgrade and the longer 81mm is the standard one. You can physically measure the increased resistance on the shorter spring. I think someone had fitted the upgrade/higher pressure to my cover in attempt to raise idle pressure on a worn engine. My rebuilt engine probably has better machining tolerances and higher pressures than an original engine so the upgraded spring then became the problem.

81mm "standard" spring fitted and all good, even when cold max pressure 60psi vs previous 80+psi.

Apologies for long post but after many, many hours checking gauges are accurate, filter specs correct, taking the oil pump base off-on-off-on , inspecting everything etc i wanted to save someone else the trouble.... or perhaps you all knew this anyway and one things for sure, I definitely should have paid more attention in Physics class to Hooke's law!
Rgds Stu

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peterc
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Location: Surrey

Re: Rover v8 oil pressure relief valve - fixed!

Post by peterc » Fri Feb 05, 2021 10:22 pm

Thanks Stu that’s valuable information for all of us with a Rover engine. It is very easy to think the longer spring would be the upgraded item plus the web site suggested the same.
They do say that the Rover engine does run with with lower oil pressures. More oil flow is more important than more pressure and less flow.
The other main criteria is a decent oil. I now use Valvolene VR1 20-50 as used by several members.
It’s the additives that are important to go with the older design engine.
Hot pressures around 25-30 on tick over and 40+ when over 1500 revs.
Peter C

Chris Pendry
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Joined: Fri Dec 06, 2019 10:03 am

Re: Rover v8 oil pressure relief valve - fixed!

Post by Chris Pendry » Thu Feb 18, 2021 9:06 pm

Many thanks for your post Stu
I have my standard Rover SD1 engine on a stand detailing and checking before the kit arrives (soon hopefully....?)
Someone mentioned I should change the 2 gears in the oil pump as a matter of course but fortunately my engine is relatively low mileage and I had the chance to run the car before I broke.On inspection all looks well with the gears so I’m just opting to change the relief valve spring with the service kit (not from Rimmers) - I will however check and compare the length of spring with what comes out - thankyou
I did have a struggle to remove all the water pump bolts - fortunately with patience heat and lubricant they were all extracted with no breaks.Even though new water pumps are readily available the long 5/16 unc bolts are getting tricky to find especially high tensile - I digress- I think this should be another topic to post
Many thanks again for your information regarding the oil pressure relief valve
Chris

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clive
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Joined: Thu Mar 01, 2007 1:18 am
Location: Perth

Re: Rover v8 oil pressure relief valve - fixed!

Post by clive » Thu Feb 18, 2021 11:42 pm

Namrick Ltd are a good supplier of Metric and Imperial bolts. https://www.namrick.co.uk/acatalog/
Cheers, Clive.

(If I'm not here I'm in my workshop or on the golf course!)

Chris Pendry
Posts: 17
Joined: Fri Dec 06, 2019 10:03 am

Re: Rover v8 oil pressure relief valve - fixed!

Post by Chris Pendry » Sat Feb 20, 2021 6:33 pm

Oil pressure relief valve kit arrived today- valve spring measured 81mm (standard) 👍🏻
Thankyou for suggestion of Namrick - they seem to have most in stock including the long unc bolts up to 5” so should get me out of trouble for the water pump

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