Dual Master for Dragsix

So I have driven my 57 for 46 years. If you can believe it, I took my driver’s test in the car when I was 16. I can’t believe it, lol, but it’s true. And all these years, I have driven on the single pot master. It failed on me just one time in 1978. Was the original master. Blew threw a stop sign and still did not understand what had just happened until I blew threw another one, lol. Limped it to the repair shop and the mechanic replaced it and showed me how to stick my head under the dash, peel the boot back and look for wetness. I replaced that master in the late 80s not for any reason other then it was old. In 2015 I had Whitepost restoration rebuild an original master and installed that when I got the car back on the highway after sitting for a number of years. So I am on my fourth single pot master in 46 years, no failures except for the first one.

My boys have both been on me to change over to a dual pot master for a while now. But the truth is I like the pedal feel I have and have always had with a single pot, the car stops fine, and other then that one episode when I was a teen, I have had no issues with the single pot. But the boys won’t let it be. And so I am waiving the white flag and will make the change over and see how I like it.

So tonight I had a little time to myself and decided to get this project off the ground. First thing, I needed a jig to mount the master on so I could add a few things to the system. What things? Well, a line loc for one. Why? Because I was a really broke teenager and I could not afford one when I was younger, lol. I don’t know that I will use it all that often, maybe at the nationals, maybe never, but I just don’t seem to be able to let that one go, lol.

The other things I want to add are inline residual valves. My car is a manual system with drum brakes. The original master had an internal pressure residual valve to keep some residual pressure against the wheel cylinder cups and the springs.

The dual masters, when new in the day, all had these rubber duck bill residual pressure valves. Two for a full drum brake system, one for a disc drum set up. The new masters that are sold today, and the rebuilt masters that are sold today do not have any pressure residual valves. They use to have them but not any longer. So I want to install a pair of Wilwood 10 pound inline residual valves to deal with that function.


That being said, the rebuild kits still come with them, at least they did two years ago. Here is what they look like. If you have an older master that has a removable brass seat in the output ports, you can use a sheet metal screw and remove the seat, rebuild the master, install the valves, and new brass seats (which come with the kit) and then you don’t need external pressure residual valves.