I was planning to rebuild the master cylinder on my 67 drum brake SS convertible. The kit costs $37.00 and the remanufactured MC costs $29.00 plus a $6.80 core. I decided to buy a rebuilt after I checked the new unit, and the casting number and style are identical. Inside the second reservoir on my original, there is a small bolt that is threaded into a hole near the fluid port. The new cylinder has the threaded hole in it, but no bolt. I am only assuming that I should swap the bolt from my old to my new. What is it for anyway?

Dave in Denver

I think that it is a mechanical stop for the piston. It is probably not used with the newer hardware.

So, do you think I should put the old piece in my new master cylinder?