Oil Pressure

[Radders]

I'm going to look at (and listen to) a 2500S engine tonight. I'm taking an oil gauge set up with me as well.

What kind of pressure should I be expecting on start up from cold and then once warm?

Thanks

[andy thompson]

Over 70 cold

When hot you want 40 to 60psi at 2000rpm
15 at idle

You need to get it properly warm to see how stuffed it is

[Nick Jones]

lagerzok wrote:

Over 70 cold

When hot you want 40 to 60psi at 2000rpm
15 at idle

You need to get it properly warm to see how stuffed it is

Agreed - especially the last part!  That one I fired up on the garage floor had great cold oil pressure  - 80psi - but could only manage about 5 psi hot idle with Wynns - which I didn't discover until after fitting it.  It did manage 40 + Psi at 2000 rpm though, even when properly hot, but still made nasty noises......  Good ones do 60+ @2000rpm in my experience.

Nick

[andy thompson]

My white PI has done 10 years hard hard work but has been reshelled twice - it has +90psi cold and about 50- 55psi at 3000rpm when it's cooking hot. It maintains 15-20psi at idle even after 10 maximum effort laps and 115-120 deg C oil temp
It does have a cross drilled crank that I think drops pressure a bit.
The oil pump is NOS and very carefully chosen to have tight clearances.
PRV spring is original slightly worn and not packed with washers ;)

[Greeks]

Is it problematic to have higher oil pressure?

[Tim Bancroft]

Graham,

The engine before last in my GT6 had very high oil pressure, I was always warned that I should encounter issues, none at all. Think I gave it to Doug F., not sure where it is now, had a nice balanced bottom end and nice light flywheel, all done by Hilthorne Engineering in Hanwell about 1985. Great engine, not sure why I took it out now!!!!

My 2.5(SU-yes, thank you PI fanatics) has 60psi at 3000rpm after being thrashed, god knows what the mileage is, 170K?, the engine is just starting to get abit fumey (Spelling?), so maybe next year for a rebuild.

Hope all is good with you in Aus (BTW I see Andy Mac has just re-joined the Club).

[andy thompson]

Greeks wrote:

Is it problematic to have higher oil pressure?

Not really - depends how high really - you only need 60psi  hot so it may be that the PRV spring is uprated   - either a different spring or packed out with small washers.

Also thick Ozzy oil can give a lot more PRESSURE but not necessarily flow -

My view is anything over 65-70 psi hot is a waste of power and puts unnecessary strain on the pump drive - especially when cold

I also ran my white PI with no oil cooler and no oil pressure gauge for about 7 years - never worried about anything then - until the oil light came on when it was stinking hot  ;D - I think Mobil 1 saved it.

[piman]

Hello Greeks,

"Is it problematic to have higher oil pressure?"

It can be, as Andy mentioned, with higher load on the oil pump drive. When I built my engine it was 100lbs/sq inch so I spaced the PRV cap with an extra washer which dropped it about 20 lbs/sq inch which I was happier with. $0,000 miles later it's still runs at 50 lbs/ sq inch hot which I'm happy with. Cross drilled crank as well, by the way.

Alec

[Greeks]

Thanks guys. I use hpr 40. It's 25 70 and maybe it's a bit thick for what i need. Gauge shows 100 plus at start up and at 2k once running for 30 mins warm is closer to 75 psi. Winter isn't long or particularly cold though so i guess I'll  leave it.

[Straight Six]

If the pressure relief valve is open doesn't that mean that the oil is by-passing the oil filter? I could be wrong; a bloke down the pub told me that  :P

[junkuser]

Don't know if high pressures damages modern oils but back in the 1950s, Ford increased the pressure setting on their V8s from 30 to 100 psi and had lots of bearing problems, thought to be due to oil breakdown.
On going back to 30 the problems ceased.
(Information from Allan Robinson, workshop manager of Metropolitan Motors, Brisbane at the time. This was the main Ford agency in Queensland)

You only require sufficient pressure to provide adequate flow to and through all bearings under all circumstances at full running temperature.  Pressure above that achieves nothing in the way of wear reduction

[andy thompson]

Greeks wrote:

Thanks guys. I use hpr 40. It's 25 70 and maybe it's a bit thick for what i need. Gauge shows 100 plus at start up and at 2k once running for 30 mins warm is closer to 75 psi. Winter isn't long or particularly cold though so i guess I'll  leave it.

Heh heh LOL - I'm using 40-70 or HPR 50 for oil consumption reduction in my old 2500 EFI until I get the fresh 2100 in it - needed a bigger battery for winter!  God only knows what the oil pressure is cold - I just don't rev it hard and don't have a gauge!

[piman]

Hello Straight Six,

the pressure relief valve dumps oil back to the sump, all oil going to the engine galleries is still filtered.

Alec

[Greeks]

lagerzok wrote:

Heh heh LOL - I'm using 40-70 or HPR 50 for oil consumption reduction in my old 2500 EFI until I get the fresh 2100 in it - needed a bigger battery for winter!  God only knows what the oil pressure is cold - I just don't rev it hard and don't have a gauge!

Hmm i kind of ... 'need' to hit 5k in 2nd to get a good run at the hill where i live  ;)