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Mental block

PostPosted: Mon Feb 10, 2014 7:26 pm
by Jentwistle3
Hi Gang! I've read through all the usual literature and I admit I must have a mental block here (illustrated below) but what is the oil pressure supposed to be? I've seen it quoted as 40 but is that at idle or at a specified rpm? My car has 40 at 2000 rpm but it drops to 20 at idle.


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Re: Mental block

PostPosted: Mon Feb 10, 2014 10:19 pm
by rgh0
The standard oil pressure relief valve is set at 40 psi so this should be the maximum pressure you see when the relief valve opens. This will normally be above 2000 rpm in an engine at normal operating temperature and bearings in good condition with the standard 20w /50 engine oil.

The oil pressure will drop at lower rpm, as the oil flow drops and the relief valve closes, as the flow from the pump is proportional to engine rpm. A typical idle pressure is in the 15 to 30 PSI range depending on idle speed, oil temperature, oil type and bearing clearances.

It sounds like your engine is behaving normally and in good condition from a bearing wear perspective


Re: Mental block

PostPosted: Tue Feb 11, 2014 6:46 am
by john.p.clegg
Nice to see someone giving the facts and not just boasting about their oil pressure,Colin said that it is not the pressure that counts but the maybe if you have tired bearings but still showing some oil pressure,you're doing fine.

John :wink:

Re: Mental block

PostPosted: Tue Feb 11, 2014 7:30 pm
by Jentwistle3
Thanks guys! This engine was recently rebuilt but unfortunately the compression was #90 in cylinder number 2, so its coming apart anyway. I'm sure that you will see more silly questions over time.