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Oil Pump & Pressure Relief Valve Queries
#1
Hi,

I'm posting the below for a friend who does not have internet access, he has just stripped and rebuilt a 3 bearing engine that was fitted to his box saloon.He has found that the oil pressure is very high after the engine has warmed up. While stripped he had cleaned out the oilways, jets and pressure relief valve. His queries are as follows:

1. The pressure relief valve was not fitted with a locking nut, so could the high pressure be due to it being screwed in too far? Is there a rule of thumb setting for this ie how many turns in should it be?

2. If the previous owner fitted a bored out/oversize pump, what is the typical pressure that would be expected when warm?

Many thanks in anticipation.
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#2
What pressure was he experiencing when it had warmed up Paul?
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#3
I just spoke to him again, it was off the scale when cold but dropping to about 15psi, this was after 3-4mins - I'm thinking he may need to run it longer to fully warm up, however he is concerned about doing damage if he has a blocked jet.
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#4
It takes 15 minutes for engines to fully warm up and they will all go off the scale when cold.

Three bearing engine can run (at normal driving speed) at 9lbs when warm but more usually 6lbs - the higher pressure is achieved by reducing the hole in the oil jet. So long as it is dropping I suspect that all will be fine.
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#5
Has he lanced the jets?
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#6
Hi Ruiridh,

Thanks, I'm not sure what all he has done. It was only when I spoke with him the second time that I realised he had only run it for 3-4 mins. I told him it needs at least 10mins and that in dropping to 15psi it seemed to be going the right way. I think he was just worried that he may be doing damage.

Would be interested to know about the setting of the oil relief valve and what pressure an overbored pump typically achieves, as it is possible that the previous owner may have fitted one.

I had noticed that the Ruby gauges have 10psi in the middle of the gauge and in my mind the needle sat around that when driving, his gauge would be a box saloon type and was expecting no more than 5psi.

He's going to try warming it up for longer and we can see what this brings.
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#7
An overbored A7 pump is capable of sustaining way more pressure than 15psi; and on a newly rebuilt engine the clearances will (one imagines) all be on the tight side. As Ruairidh suggests, a blockage is the thing to worry about, but if the jets and oil are clean it should be fine. I doubt you can do any real mischief with the PRV. The question I would ask is what grade oil is he using? A straight 30 or 40 is pretty heavy from a cold start in winter and will send the pressure way up. A multigrade will flow much more readily.
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