Yeah apparently they all have them in there except the tin type "Cooper S" master cylinder. I've run it like so since forever and there is plenty of meat still left on the Black Stuff pads and rotors... so not sure if is a big deal?

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Lillee - 1969 Morris Mini K

IMO there would be more Minis running around now with front discs and the restrictor valve still in the MC.
These things are not a check valve, they just restrict the return flow a bit.
If you can wiggle the pads in the caliper, there is no problem leaving it in.

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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.

slow return valve... it`s there for your drum brakes ... they are still on the rear of the car



without the valve you won`t be able to "Pump-up" a brake pedal when your shoes run low & are in need of adjustment

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Leaving it alone sounds great to me
Really appreciate the info from all!
Enjoy the fun Zulu!

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1975 Clubman
1152cc, 40dcoe weber, RE83 cam, GRed head.