6 replies to this topic

[SomethingNew71]

Hey Folks!

 

Recently had a drop in oil pressure that ruined my motor.  I rebuilt it and got it to start back up for the first time tonight.  During the 1-2 mins it was running I had an oil pressure of about 95 to >100 and then got really nervous about it and turned it off.  Is this normal?  I mean I know new motor can be tight and all but still made me uneasy.

[russo]

Are you running a piston or ball type relief valve? The ball type seem to run a lot higher. I'm running a ball type and ran at 120 psi for several thousand miles, didn't seem to do any harm. Have just recently reduced it to 75 psi by shortening relief valve spring.

[Stevie W]

Hi,

 

As Russo stated, the ball bearing relief valve can make the oil pressure higher and reducing the spring length will bring it down a bit. 

Massively high oil pressure isn't a good thing to have. It tends to use more engine power as the pump is working harder against the pressure relief valve, this can also unnecessarily raise the oil temperature which isn't desirable either. 

 

Most people opt for the original "bullet" type and spring which should give you about 40-ish psi on idle when cold and up to 60 psi when driving. My own Mini has the ball bearing type and my oil pressure stays around 70 psi constantly, which as mentioned above just uses more power and raises the oil temp.

 

I'm changing mine back to the bullet type soon!

 

Cheers, Steve.

[MRA]

The ball type are really only for racing, not road use, the reason is because of how each type work or sometimes don't work...

 

Your ball type will fluctuate, you won't see this on the gauge but the engine will "see" it as pressure waves, this is bad for a road engine, this type are less susceptible to debris in the oil causing the valve to stay open which is good for racing.

 

Your plunger type which maintains a much better more even flow, allowing better control of oil to your bearings especially at low engine speeds where most road engines seem to spend a lot of their time.

 

You may notice if you read your Mini history books that neither Morris, Austin, BMC, Leyland nor Rover fitted a cheaper ball type PRV except to the one Cooper S in the 60's everything else was fitted with the more expensive plunger type, none of the companies above spent money when a cheaper option was available unless there was a very good reason for it.

[SomethingNew71]

To answer the questions a few of you asked I have the stock plunger type relief valve installed.  I bought a ball bearing type but I have yet to install it.  I wanted to make sure it worked stock before I did anything like that.  

[Matt's Dad]

If you are seeing 120psi with a plunger type relief valve and the standard spring (rather than the visibly different spring from the ball bearing set up), it's potentially the plunger sticking or even seized in the bore.

It's worth checking that the plunger can move freely and that you haven't got the wrong spring in there. From memory, the ball bearing set-up spring is actually shorter free length than the plunger type, but has heavier, tighter wound coils. 

[carbon]

Hey Folks!

 

Recently had a drop in oil pressure that ruined my motor.  I rebuilt it and got it to start back up for the first time tonight.  During the 1-2 mins it was running I had an oil pressure of about 95 to >100 and then got really nervous about it and turned it off.  Is this normal?  I mean I know new motor can be tight and all but still made me uneasy.

You haven't said what grade oil you're running. If it's 20W50 then 90-100psi on starting from cold is not unusual, and this pressure won't cause any damage. This is what I see with my 1275 using 20W50, once the oil is warm after about 5 miles it drops to about 50psi at tickover.

 

I would advise against the ball bearing relief valve. I fitted one many years ago and the pressure went much higher on starting from cold. So much so that one very cold morning it was well off the gauge and probably at about 120-130psi when one of the oil gallery plugs blew out (it was the the one at the flywheel end, engine out job to replace it).

 

I have stuck with the thimble type oil pressure relief valve ever since, and not had any issues.