What is the diff between master cylinders for early model 914's (70 - 72) and late models (73 - 76)?

Functionally speaking are they interchangable or not?

I'm curious as it seems the 914-6 or early model 914's have ATE masters at a reasonable price.

I'm gonna bet the -6 MC is essentially the same as the 911 MC of the same years. I think the -6/911 MC is a 19mm and the -4 is a 17mm. And most of the vendors sell the 19mm at a lesser price than the 17mm. I bought a 73 911 MC for my car and installed it. There is discussion about pros and cons of each MC; search here for threads on that. Check out Eric Shea's site PBPerformance for optimum brake parts ... (or GPR, Pelican, ....). One difference I've read is if the switch on the MC has a terminal for ground or not; I've seen lots of questions about what to do with the "extra" wire.

Also, check out PET 604-00 for part numbers...

AFAIK, the only difference is that the Sixes had the 19mm master cylinder, while all of the four-cylinder 914s had the 17mm one.

--DD