Hi,

I fitted a Minispares spring and ball kit to my engine and removed the old plunger and spring. My oil pressure shot up to 90PSI whilst idling, I cut the spring down and it dropped to around 50PSI, though the oil is coming out of the dipstick.

I Know that with the old plunger & spring this never happened.

Any advice as to what I should do??

Thanks Roc

Roc,

Sounds obvious I know, but put the original plunger & spring back in!

Then things should return to normal, if not then there's another problem in there.

I sounds to me that the ball is getting jammed for some reason, hence the stellar oil pressure.

Why did you replace the plunger? Was it causing trouble? I prefer the plunger type on a roady typically, never had an issue with them.

cheers

Jacob

_________________
'72 Clubman Van - 1022cc, 295 head, 731 cam - Daily Driver
'69 Morris 1100 S - Dinged by a bus, in shed under repair
'64 Morris 1100 - Early 1100, long term project

I prefer the 9/16" ball, it actually seals better at idle and gives you better pressure.
However...
1. You need to cut 2-3mm approx off the spring or the pressure will be higher. Fit the cut end outwards. But 90psi cold is OK, it'll drop to 70-75 when hot.
2. The spring can bend around on the ball and push it sideways off the seat. To prevent this, I put a piece of 5/16" dia steel rod, 40mm long, inside the spring. It's worked fine on the 12 or so motors I've done this to.

_________________
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'm sure this has been covered in a hundred posts, but what should oil pressure be at idle? Mine drops to ~20psi at idle and ~between 50 & 70psi when driving.

_________________
1970 Mini Deluxe - 1275, Weber, Clive 346 cam, MS 4-pot slotted discs, Megajolt ignition Now with new improved Mambas... almost on the road
1966 Van with Traveller rear seat conversion
2008 Prado GXL
All in various states of repair...

That's fine Dave, nothing wrong with that. The nearly-10-year-old build in my car currently does about that, 70psi max when cold (or more accurately, not hot) but drops to ~25psi at idle and ~55psi at revs when HOT.

_________________
Simon

The adventures of an owner builder in the Tallarook Ranges

You probably have a ball and spring set to traditional factory Cooper S oil pressure. The oil pressure at idle will always be close to 100 when cold, and will drop to more normal idle oil pressures once the oil heats up.

Pressure above idle with this spring combination will always swing towards 100 whilst the oil and engine is in good condition. The spring is now cut down however and won't be able to perform as it was intended.

_________________
SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Cooper S here never had a ball, from what I can gather. Neither of ours did. They both did have a heavier spring though.

_________________
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.

Thanks doc. Yes, that's what I meant. The ball and spring replacement for the stock set up are set to the same setting as the factory S spring and plunger.

_________________
SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

I don't mind the higher oil pressure, though it is spitting oil through the dipstick and causing a mess to the front of my engine, as well as my driveway??

is there a mod to provide better sealing to the dipstick??

No matter what your oil pressure, it should not spit oil out the dipstick tube.
Are you sure you haven't done anything else, like overfilled it or blocked off one of the breathers?

_________________
Too many cars, and too little time.

No, all I did was change the spring & ball.

I will re-insert the old spring and plunger and will see what happens.

I don't think that is right either. The ones I have bought have included a stock Cooper S spring and ball, which, installed that way (uncut), will produce excessively high oil pressure, as the spring sits "on" the ball and not "in" the plunger. I have always had to shorten the spring, sometimes cutting off 4 - 5 coils to bring the oil pressure back to where it was. I also do Kev's trick of the short rod inside the spring. I do set it up to run no more than 65 - 70 psi hot.

_________________
Steve

Fair enough. The ones I have picked up I thought behaved the same. I've got another one here I was going to throw it in the new 998 engine.
I'll see how it behaves once fitted.

_________________
SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

What sort of block have you got (A or A+)?

Done a compression test lately?

_________________