Got a leaky proportioning valve which is a FAM4670. I can get it off karcraft for an alright price but was wondering how it differed to FAM7821 - is it just the thread size or is it fundamentally quite different?

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1978 Leyland Clubman

I can't off the top of my head remember which is which, but 1 has 4 ports the other has 5 ports. A direct replacement for the ones fitted to the Oz production Clubbies is a 5 port.

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You can refurbish these. If it's leaking, replace the o-rings.

You put the value in a clamp length-wise to push the cap in, and fold out the steel tabs on the 'capped' side. The end will come off and you can take out the spring. Take the big bolt off the other end, and remove the small spring and rod. You can then put a screwdriver in the slot and a small socket in the other end to remove the small nut. The plunger can then be removed, and you can replace the two o-rings. It can be done in 10 minutes.

True, but (and I perhaps should have suggested before) I'd suggest throwing it in the bin! Fit a Pressure Shut off valve from the early cars or better yet, a proportioning valve from a late Moke. Mini King has them.

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So what's the other option considering i'm starting with the tandem circuit master cylinder?

Is the pressure shut off valve you're talking about the 21A1774 on the rear subframes?

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1978 Leyland Clubman

Yeap. Even though it's a Tandem System, the old style pressure shut off valve will work. This is all that that later one did anyways.

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Wouldn't you still need a splitter for the front lines then?

I really don't know anything more than dual circuit systems, because that's all I've ever done. The pdwa valve found on dual circuit minis is essentially a cut-off value with a splitter attached - how are the old style ones better?

The old style ones are far more reliable. Mine is 43 years old original and still working.

To get rid of that FAM valve you run the rear circuit straight down the firewall then replace the rear tee on the subby with a pressure limiting valve.
I don't know if these are still available new, Mini King had some a while ago. As for their seal kit though I've been searching for years. The Lockheed kit is NLA.

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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.