My drum brake master cylinder is leaking. I plan on upgrading to discs in the future. Will a disc brake mc work with my drums so I don't have to buy 2 new master cylinders?

Yup no problem.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

That's what I thought, just wanted to double check.

Hey Dan, not trying to be contrary, but are you sure?

iirc, it depends on what wheel cylinders you are using... the earlier ones needed a residual pressure valve (in the MC), whereas the newer wheel cylinders and 'problem solver' wheel cylinders had an expander built into the wheel cylinder.

Or am I just confused and the residual pressure is handled by the drum brake combo valve?

RP valves went away when wheel cylinder seals were revised in '73. It is highly, highly, highly unlikely there are any old-style wheel cylinder seals are still in the current parts market.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

My car is a 73 and I when I got it, it had a disc brake mc. It leaked but seemed to work fine.