Need advise on master cylinder and related parts

[junkyardjeff]

When I put discs on my 55 sunliner I just put on a dual master cylinder and plumbed in a adapter for the switch and that was it,no residual or proportioning valve and it works just fine.  Now I am working on my 37 chevy p/u and the master cylinder is under the floor and I heard I need to use residual valves,I have found two master cylinders at the local parts store that has the lines on the right side and I need to know what to do with either one.  One is for a 87 to 96 ford truck that has a screw on proportioning valve for the rear brakes and the other is for a 73 to 79 ford truck that of course has none,what do I need to do for either master cylinder.   Jeff

[kb426]

The reason you need residual valves is because when the master is lower than the wheel cylinders, the fluid will drain back causing air to be in the cylinder and the spongy pedal. There are no calipers that I have used that won't do this occasionally. Residual valves for discs are 2 lb. and for drums are 10 lb. There are some masters that have the valves built in. I'm not much help in telling you which ones.