Morris Minor Owners Club

Just answered a question about the adjustable oil pressure relief valve on the MMOC Facebook page and thought I would post on here.
The valve has been replaced with a 5/8" ball bearing, a ball bearing cup, a shortened spring, a top plate for the adjuster screw to press against (otherwise the adjuster screw goes down through the centre of the spring) and a modified cap with 1/4" UNF adjuster cap headed screw with locking nut.

Phil

That looks like a useful modification what is the normal pressure setting?...Also does the ball sit in the conical seat within the block and does that normally need any work whilst carrying out this mod if the seat is worn or high mileage?

Taupe

60psi is a good working pressure. Anymore and all you are doing is making heat and taking power.
The ball sits in the conical seat of the insert in the block. Normally no work is required to fit this mod. If the insert is worn it can be re-ground (see BMC wksp manual for details) in place and the inserts are available and relatively easy to replace. This mod has been around for a long time - all I have done is refine the details.
Below is a drawing of the insert:-

Looks good Phil.
Does it leak oil past the adjuster screw?
I suppose the diameter of the ballbearing/spring cup is the same as the standard pressure valve?

The oil does not pass through the threads of the cap/adjuster screw.
Edit: The original spring cup is 5/8" dia and ball bearing is 9/16" dia."

I have to say that shortening the standard spring Pt No 6K853 is really of no benefit. The main benefit in fitting the ball bearing is that it has less tendency to jam either in the open or closed position than the cup type valve.

Hi,
I followed Phil's advice on here many moons ago and fitted the Mini ball bearing with the original spring, this improved the oil pressure and, as stated (and I found and had to faff about to get it out!) the ball bearing doesn't jam in place like the original cup valve did.
Link to original post below.
Best wishes,
Mike.

https://board.mmoc.org.uk/viewtopic.php?t=53440

I agree with the sentiment that shortening the spring is no benefit. But you need to shorten the spring to make it fit together. If you do not shorten the spring you will not be able to adjust the oil pressure and you may even have the spring bind in that the ball or cup is unable to be lifted off its seat to release excess oil pressure. It is a matter of trying the fit and seeing what you can do about the oil pressure with the adjusting screw. You may even have to have one or more goes at getting the spring length right. As for getting the ball out of the block use a magnet shoved in the end of a piece of rubber pipe.
In my original post above the ball bearing size should read 9/16" (made the same mistake in my 2013 post - will I ever learn)
As a result of my 2013 post regarding the difficulty in removing the release valve cover with the starter in place I made a special socket which allows me to remove the cover without removing or slackening the starter motor.