Dual Master Cylinder

[Cowboy91]

I have an Avanti II, RQB1532. The guy I purchased it from started a retro on it but really didn't have a clue of what he was doing. My question is the dual master cylinder he replaced or placed on the MasterVac. The question is if it common that the rear chamber of the master cylinder is the only one used. In the past when upgrading from a single to a dual system, the rear chamber operates the front brakes with the front chamber operating the rear. If both chambers are to be used, is there a conversation kit for the plumbing or am I on my own. Thanks.

Edited July 27, 2014 by Cowboy91

[Gunslinger]

There's no question that both chambers should be used or there's no point in having a dual master cylinder. While it's not universal that the rear chamber powers the front brakes, it is the norm.

Your car by serial number must be a 1970...it's only 42 numbers before my car which was assembled in September of 1970. It would definitely have been equipped with a dual master cylinder when built. Beginning with the 1967 model year dual master cylinders were required by federal law.

Contact either Nostalgic Motors or Studebaker International as they carry the parts you need. A word of advice...if you don't know if all the rubber brake lines have ever been replaced, get new ones at the same time. Check the metal lines very carefully as well and replace if anything looks wrong. Brakes are too important to take halfway measures with.

[Cowboy91]

Gunslinger, thanks for the response. Yes it is a 1970. According to the production sheet, 17 Apr 70. I'm with you on the brakes. Fronts new pads and hoses, Rear shoes were okay but had to rebuild the wheel cyliners, replaced the drums and install new lug studs, new hoses and metal lines. I know little of the car's background other than it was for sale in 2004 as a body, frame, front suspension but no rear axle. It does have a tapered Dana 44 in it so someone matched the the factory specs. Always wanted one since high school in the early '60s. Will go nicely with others in the garage.

Edited July 27, 2014 by Cowboy91

[warren55]

The distribution block/proportioning valve is similar (or perhaps identical) to a late 60's (69 or later, I think) Mustang or the Mustang II. You can probably use whatever you can find from a front disc/ rear drum car in that era if you can make the plumbing work. I think there are some photos floating around here on the forum that I posted of mine, and I believe a couple others have posted also.

Mine is a 73, so it could be slightly different than yours was originally, but I can supply some pictures if you need them. If you're not worried about staying original, there are some good aftermarket options, too.

[Gunslinger]

Starting in '71 Avanti used different rear brakes...self-adjusting in place of the eccentric nuts on the previous Avanti design. They're still 11"x2" but use different shoes, wheel cylinders and drums.

For a '70 you can get the stock distribution block from any of the normal vendors...Jon Myer, Nostalgic or SI. You can also go to sites like Summit Racing or Jegs and get an adjustable proportioning valve, though that will take some getting it adjusted properly.

[Cowboy91]

Thanks to all for your comments and ideas. The folks at Avanti Parts and Restorations help me with the "how to" in solving the piping on the dual master cylinder. I'm going to put it together without a proportioning valve for now. If I get rear lock up, I'll add it. I happen to talk with a individual working on a '64 Lark conversion (engine, trans, brakes) who offered to give a hand in exchange for some welding he needs done. Help is help.