This is my replacement 1100S motor.
It looks like my oil psi falls the longer I drive the mini. When cold it sits around 60psi when the engine warms up it's around 40psi but after that the gauge starts to drop worryingly to 20-15psi while driving and down to 5psi at idle . It isn't affected by engine temp at this stage (after about 30min driving) I've had the engine temp right up and right back down, the oil psi stays low.
The engine did have a oil cooler in it's previous car but i have not ran it with the cooler in my car and I'm using KMX 20-50 with 1L of castrol 20-50 although my old engine never had a problem with mixing these oils and it ran between 40 and 80.
Would refitting the cooler help?
I should add I still drive it but I feel like it's a bad thing waiting to happen, the engine seems fine and I cant tell any difference in the engine through the different psi's, the oil looks nice and clean on the dipstick, new oil & filter, the oil warning light has never come on while the engine is running.

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Respect mine and I'll respect yours.

that's what KMX was doing in my current motor, just didn't maintain pressure, though never went that low. I went to Fuchs Formula 60 - never drops under 50psi

but.... if it's an old & unknown motor (unknown to you, no matter how good the previous owner said it was) then maybe it's just time it had some bearings put through it

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did I tell you that I won a trophy?

I currently run Valvoline Classic 20W/50- on the Rylstone gig last year, my 1412 sat on 75psi all the way up there and back. No cooler. Was a fresh motor though.

What relief valve spring is in it? You could pack it out a bit (say 3mm) to see what happens, or fit a Cooper S spring (are stronger than the old common A series ones).

Could also be the relief valve plunger is worn- I use a 9/16" steel ball in my motors instead.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I might try an oil change on the week end.
Hey Doc what's involved in the stuff you suggested.

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Respect mine and I'll respect yours.

1. Make sure the spring is straight, or get a new Cooper S one.
2. Pinch a CV ball (9/16") or go buy a new one from a bearing shop.
3. Grind a chamfer inside the best end of the spring so it sits on the ball better. I use a pointed stone in the die grinder. It's not essential if you can't do it.
4. Cut a piece of smooth 5/16" or 8.0m steel rod 40mm long, deburr the ends and put it inside the spring. This stops the spring bending and pushing the ball sideways off the seat (with instant oil pressure drop).
5. Remove the old relief valve plunger. I use a 10mm dynabolt, put it inside the plunger and then do the nut up a bit. Then you have a handle to pull the sucker out with. But sometimes they come out easy with your finger (if the right size).
6. Assemble it all into the valve, refit the cap, start engine and check pressure. If it's too high, trim 2mm or more off the outer end of the spring.
I run mine @ 70-75psi hot from 2500rpm up. Cold, it's ~90psi...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

IT does sound like you have a problem, either engine bearings or pressure relief valve is worn?
A new engine should have 75 lb when cold and during highway driving, above 3000rpm, and a minimum of 25lb at idle when hot, although my new engine is still idling with 40-50lb when warm

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1969 Cooper "S"
1967 Mini Deluxe
1973 Clubman Van (the fleet spare)
1978 ex 1275 LS ("Wizard" Eaton Supercharged)
2015 HSV GenF GTS(occasional drive & tow car)
2019 MINI F55 Cooper S

This might be an obvious one, but it could be the oil pump too. If you've had anything break in the gearbox the swarf can make it into the pmup and wear it down. They're very robust, but they can wear out, and I have heard of the shafts breaking too.

Id say an oil change should be the first on the list.

At hay this year I ran the last half of the Khana with less than 5psi... Between 3 drivers hahaha somehow survived! Then got a loose fanbelt and snapped the handbrake out of the floor during the heroes. Man I had alot of problems that day. Shame as when it ripped out I was infront of rid shaw who went on to win the event always next year

got a mate who is having the same problems ! still searching for answers.

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That's why it's good to be.............ME

I meant to swap the oil today but didn't get a chance, I'll hopefully get it done tomorrow and see what that dose.

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Respect mine and I'll respect yours.

Hhhmmmm,,, doesn`t sound good kenno

yeah maybe try an oil change & the oil pressure relief valve , but im not too sure it will fix it

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Changed the oil on Sunday (from KMX to Penrite HPR30) and went for a drive, it did help raise the level by 5psi when hot. Picked up a new spring this arvo so I'll try and swap that next weekend, fingers crossed it fixes the problem.

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Respect mine and I'll respect yours.

I'm a bit concerned about the HPR30? I would have used 60 grade if I was trying to raise the oil pressure

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1969 Cooper "S"
1967 Mini Deluxe
1973 Clubman Van (the fleet spare)
1978 ex 1275 LS ("Wizard" Eaton Supercharged)
2015 HSV GenF GTS(occasional drive & tow car)
2019 MINI F55 Cooper S

HPR30 is a 20W/60, I think. Been years since I used it... it sludged inside my rocker cover in 1000 miles.
Yep I was right- http://www.penriteoil.com.au/products/e ... um_mineral

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yep 20/60

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Respect mine and I'll respect yours.