My master cylinder crapped out on me, and I need a new one before I go on a cruise next weekend. The trouble is, I want to upgrade to rear discs soon, but not immediately.

Can I use a 4 wheel disc master cyl (69 vette is what I'll specify)and use my adjustable wilwood proportioning valve to get it "right" for the rear drums??? Has anyone tried it?

I'm cheap and I don't want to buy a master cylinder twice graemlins/clonk.gif BTW, sorry for the double post, but I gotta know soon so I can order and have it on by the weekend.

I work at napa and the part # is the same for a disc/drum master cylinder and one for a corvette??!! So if I where you I would buy one from a company like MP brakes, otherwise you might not have the right amount of pressure/volume, whatever is needed for a disc/disc setup. I called my manufacture of my masters and they said they are designed for both applications. I dont know how that can be.

You need to know if you need a deep hole piston master or shallow. Take the old master off and check. Most deep hole masters are 1 1/8 dia. The shallow are 1 in dia. I have the stock vacuum unit and I am using the 1 inch diameter shallow piston master for the Corvette. You may be able to find a deep hole piston in a 1 inch master.

65Camino
Team Chevelle Member #74
355ci. 700r4 diskbrakes 3.73 Auburn Posi.

I would not pay the price that MP Brakes charges for their master cylinders (about $119.99 for a 1-1/8" disc/disc unit). Go to your local parts store that is an AC Delco distributor and buy a new (not rebuilt) one. 1969-76 Corvette disc/disc 1-1/8" bore power brake master cylinder with the deep pushrod seat piston is p/n 18M72 and wholesales for $66.34 and 1977-82 Corvette disc/disc 1-1/8" bore power brake master cylinder with the shallow pushrod seat piston is p/n 18M91 and wholesales for $62.55 at my local parts joint. Why pay more?