13 replies to this topic

[Gibbo]

Ok so for the rebuild I have purchased a replacement ball and spring for the oil release. Main question, how do I fit it? not attempted yet, it may be obvious

a brief explanation of fitting the ball spring and dome cap to the block would be great ie which? ball or spring first.

[GraemeC]

Ball then spring then cap.

[Gibbo]

Thankyou kind sir

[Grayedout]

And make sure the new spring that came with the ball is shorter than the old spring you took out or you will be running too much pressure !

[Gibbo]

ok, cheers.

is that because they stretch slightly or because the ones with the balls need to be shorter than the standard ones?
I must admit i'm tempted to replace the clock in the dash with an oil pressure gauge so I can keep an eye on it.

[dklawson]

A spring produces force proportional to the amount of its deflection, more deflection = higher force. The standard relief valve spring sits in a pocket on the back of the relief valve plunger. When you replace the plunger with a ball (which has no pocket) the standard spring is compressed more. The rule I remember is that you cut three coils off the standard spring to get it close to the correct relief pressure. If necessary, you add washers between the dome nut and the spring to bring your operating pressure back up a bit.

You bought the ball and a new spring but you didn't go for the adjustable kit? With a little more effort, you can modify the dome nut to accept a 1/4-28 or M6 bolt to push against the spring from the outside. This lets you dial in the pressure you want.

[Gibbo]

Ah ok then.

didn't go for an adjustable as didn't realise you could get them to be honest, placing a bolt in the dome may be worth it. Although I think i'll see what pressure i'm actually getting before going through the effort, I bought a new spring etc just because i was replacing a load of bits and figured I might as well whilst it was out.

One question actually, not sure if haynes states but on the mpi there are 2 holes my the electronic start, one for the oil switch and one for the pressure regulator, one above the other. Anyone now which one goes above the other?

[Sprocket]

There is a Cooper S oil pressure ball and spring kit, the spring is the right length when fitted with the ball and should give 75psi

[syholl]

When you remove the old spring, make sure it comes out with the plunger as well. They can get stuck in place, and you wouldn't want to put the ball bearing in as well as the plunger...!!

[1984mini25]

Hope this helps,
All you do is remove the old plunger and spring, then trough in bit of keep in a safe place.

The put the new ball in first followed by the new spring and refit the big nut, using a new copper washer to prevent any oil leaks, there done.

[Gibbo]

Thats quality, cheers guys.

[dklawson]

Not to beat a dead horse here or anything... but since I don't know what exact parts you bought, I still suggest you lay the parts out on the bench comparing the length of the old spring (inserted into the plunger) to the combined length of the new spring and ball. If you find the overall length of the new parts is a lot more than the old parts (and yes, 6 to 8mm is a lot)... cut coils off the springs. Don't just slam the new parts in without comparing the new and old.

[Gibbo]

cheers, I'l make sure to check.

I bought the ball and spring as a set from minispares, so technically I guess it should be the correct shorted spring.

But I will check still.

[1984mini25]

ball and spring as a set from minispares

The spring is actually longer with the minispares kit, as the ball is smaller than the plunger.

Just stick what you got from minispares in the engine and it'll be fine.