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Oil Pressure Sprint
Posted: Fri Aug 13, 2021 1:49 pm
by Damson6
Recently rebuilt engine and has done about 200 miles, I have changed oil and filter, oil now is classic 20/50 but I am concerned as the oil pressure is 80psi at 2500rpm when hot and goes to nearly 90psi at 3000rpm.
Is this too high? everything else seems fine. Oil pressure on the running in oil was much the same.
Derek
Re: Oil Pressure Sprint
Posted: Fri Aug 13, 2021 2:48 pm
by cleverusername
Damson6 wrote: ↑Fri Aug 13, 2021 1:49 pm
Recently rebuilt engine and has done about 200 miles, I have changed oil and filter, oil now is classic 20/50 but I am concerned as the oil pressure is 80psi at 2500rpm when hot and goes to nearly 90psi at 3000rpm.
Is this too high? everything else seems fine. Oil pressure on the running in oil was much the same.
Derek
That sounds a little on the high side. When they rebuilt the engine, did they fit a new oil pump?
I have heard that some oil pumps have the wrong spring on the pressure relief valve, meaning it opens at too high a pressure.
Re: Oil Pressure Sprint
Posted: Fri Aug 13, 2021 5:47 pm
by Damson6
cleverusername wrote: ↑Fri Aug 13, 2021 2:48 pm
Damson6 wrote: ↑Fri Aug 13, 2021 1:49 pm
Recently rebuilt engine and has done about 200 miles, I have changed oil and filter, oil now is classic 20/50 but I am concerned as the oil pressure is 80psi at 2500rpm when hot and goes to nearly 90psi at 3000rpm.
Is this too high? everything else seems fine. Oil pressure on the running in oil was much the same.
Derek
That sounds a little on the high side. When they rebuilt the engine, did they fit a new oil pump?
I have heard that some oil pumps have the wrong spring on the pressure relief valve, meaning it opens at too high a pressure.
Yes new oil pump and pretty much else as well.
Will have a look and see if I can tell what make it is?
Re: Oil Pressure Sprint
Posted: Fri Aug 13, 2021 7:21 pm
by BobM
Hi Derek,
Yes the oil pressure is too high. Pressure should be between 40 to 60 PSI. Above this the oil may in the longer term scour the soft shell bearing material. Another issue will be the added load on the jackshaft and distributer gear. This will accelerate the wear on these gears, the spec of which is already minimal.
If you bought your pump some years ago this warning from Robsport may be of note.
'Oil pump
(Product)
Oil pump PLEASE NOTE : All of these oil pumps have been made with the incorrect pressure relief valve spring , so you need to use the one from your old pump .They give far too much oil pressure and ...
Created on 31 July 2013'
Hope this helps,
BobM
Re: Oil Pressure Sprint
Posted: Fri Aug 13, 2021 7:44 pm
by Damson6
BobM wrote: ↑Fri Aug 13, 2021 7:21 pm
Hi Derek,
Yes the oil pressure is too high. Pressure should be between 40 to 60 PSI. Above this the oil may in the longer term scour the soft shell bearing material. Another issue will be the added load on the jackshaft and distributer gear. This will accelerate the wear on these gears, the spec of which is already minimal.
If you bought your pump some years ago this warning from Robsport may be of note.
'Oil pump
(Product)
Oil pump PLEASE NOTE : All of these oil pumps have been made with the incorrect pressure relief valve spring , so you need to use the one from your old pump .They give far too much oil pressure and ...
Created on 31 July 2013'
Hope this helps,
BobM
Thanks Bob
Pump was bought last year so not sure on that but could be old stock?
I haven't got the old PRV so will buy a new one and see if its any better?
Just ordered a new one from Robsport so that shoud sort it, I hope it states in the instructions which way round it goes.
Derek
Re: Oil Pressure Sprint
Posted: Thu Aug 19, 2021 4:36 pm
by Damson6
Sucess, fitted my new spring from Robsport and it's now running 60psi max and 40psi at tickover hot.Result thanks all.
Derek
Re: Oil Pressure Sprint
Posted: Thu Aug 19, 2021 7:24 pm
by yorkshire_spam
Damson6 wrote: ↑Thu Aug 19, 2021 4:36 pm
Sucess, fitted my new spring from Robsport and it's now running 60psi max and 40psi at tickover hot.Result thanks all.
Derek
Great result!
Re: Oil Pressure Sprint
Posted: Fri Aug 20, 2021 8:59 am
by tangocharlie1
I had the same issue last year and a new PRV spring from Robsport solved it, not sure how wide spread this is known, but maybe a mention in the club mag wouldn't go a miss ?
Re: Oil Pressure Sprint
Posted: Fri Aug 20, 2021 8:59 am
by tangocharlie1
I had the same issue last year and a new PRV spring from Robsport solved it, not sure how wide spread this is known, but maybe a mention in the club mag wouldn't go a miss ?
Re: Oil Pressure Sprint
Posted: Thu Aug 26, 2021 9:59 am
by Damson6
I am informed by a Stag specialist (same pump) that they too have had the same problem to the extent that you can here the valve banging!
It's not good to think they are still selling the pumps with the wrong spring after all that time?
Re: Oil Pressure Sprint
Posted: Thu Aug 26, 2021 1:18 pm
by Carledo
I found one a couple of years ago on a rebuilt motor I fitted for a customer. It blew the oil filter seal (spin on conversion) on first startup and deposited half a gallon of oil on the floor before I could switch off! Suspecting something of this sort I connected up a guage and found it had almost 100 psi of cold pressure at idle. A good used stock spring cured that!
Steve