oil pressure relief valve spring

[izzi]

What problems can a longer spring cause? As the the new one I have is about 1cm longer. My reason for asking, is that I have been told that a new spring and valve will force a oil leak at the rear crank shaft area. Especially after having a new oil pump fitted.
Thanks.

[bmcecosse]

If the pressure is too high - and the bearing worn - then certainly it will flood the labyrinth and increase the chance of a leak. Assuming you have an oil pressure gauge - just use the old spring and check the pressure. If it's ~ 60 psi at 60 mph when stinking hot after a good run - then it's fine ! 20 W 50 oil of course.......

[mike.perry]

The biggest problem will be trying to fit the longer spring

[fsk658]

If you want to check your old spring measure the length as stated in Haynes Workshop Manual on page 14 it states free length of 72.63mm and a fitted length of 54.77mm but how you measure the fiited length I dont know.

[katy]

Do both the old and new springs have the same size wire in them?

[bmcecosse]

It really really doesn't matter........

[chris_bates]

Roy,

A longer spring with the same wire width and material will cause the oil pressure relief valve to open at a higher pressure than a shorter one. I go along with bmcecosse in that if your existing spring is producing 60psi at 60mph then that is plenty strong enough. In a racing mini engine, the spring would be shortened to give a reading of no more than 25psi as higher pressure causes more drag on the engine internals. But then you don't want to be rebuilding your engine every other weekend!

The other thing to watch out for is that a number of replacement parts sold for our cars are sourced from businesses that have a part for another purpose and it happens to fit the Minor reasonably well. Also some made to measure parts are I'm afraid less than perfect. You may therefore have a longer spring but a weaker spring which does the same job as the original. The only way is to test it and see what psi you get.

Chris

[bmcecosse]

I've built a few 'racing engines' and believe me - they won't last 2 minutes with 25 psi..... The spring is NOT shortened - quite the reverse - although most are used with a 'ball' valve - and not the standard plunger. I know all about springs - but the intricate detail of wire size etc really doesn't matter here - it just needs to give 60 psi at 60 mph on a HOT engine. That's what matters.......
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