My truck uses its original 4 drums
I did a complete 100% brake system replacement using a 1967 Ford fairlane dual master cylinder--the MC is for a 4-drum brake car, NOT a disk car. RAYBESTOS MC39495
All wheel cylinders were replaced, and all lines for entire truck replaced--no leaks. I also bought quick bleed valves for fun.

Residual valves are generally only intorduced when using disk brake combos(i have read/been told); and they tell you to check the master for the "little rubber things" and that will tell you if they have residial valves built in. My '67 MC is for a 4-drum car, and the damn thing will not keep pressure...............but I thought residual valves were not needed for drum only vehicles?


I'm tired of pumping my breaks even with a brand new system. Will the installation of residual valves help me?

 

Drum brake MC's have RPV's but only 2-3 psi. The RPV's may not appear to be rubber, they are sometimes retained with a metal piece. Are you sure your shoes are adjusted?

 

Yes the shoes were adjusted when new, and again at a later time. Made zero difference. I adjusted them to have noticeable, but little drag.

 

https://www.strangeengineering.net/u...ressure-valve/
https://www.wilwood.com/search/partn...sidual%20valve
https://techtalk.mpbrakes.com/how-to...valve-overview
With the master cylinder under the floor, below the wheel cylinders, it's even more important to have the RPV's to prevent backflow and wheel cylinder drain.

 

ALL 1967 and later FoMoCo vehicles with dual master cylinders have a brake pressure differential valve that some peeps call a proportioning valve. I've never heard of a residual valve.

C7OZ-2B257-C .. Brake Pressure Differential Valve / Obsolete

1967 Comet, Falcon & Fairlane with drum brakes. The valves used in all 1967 FoMoCo vehicles were 1967 only!

IF this Fairlane had disc brakes, it would have used a different master cylinder, different valve (C7OZ-2B257-D) and also would have had this puppy mounted on the rear axle:

C7OZ-2B091-B .. Front Disc Brake Pressure Control Valve = 1967/69 Fairlane/Falcon/Comet/Mustang/Cougar.

 

I actually still have that "splitter" valve thing connected to the brake lines. My dad had a junk '67 fairlane that we tore to pieces. That car is what inspired me to use the 4-drum MC out of a fairlane.


Would I need one valve per wheel or can i just use two valves--one valve per MC output line?

 

Brake pressure differential valve located below the master cylinder, lines routed from the cylinder to the valve, then routed from the valve to the front and rear brakes.

You need this puppy to get the brakes to work properly.

 

As long as the valve is inline before the split to the wheels, you are good with one per circuit.

 

That differential pressure assembly is to set a warning light that one circuit has failed, it isn't any kind of RPV, and is not necessary if you don't have a warning light.

A quick websearch turned this up; your MC may not be for drum/drum after all:

 

which of the two outlets is for the front brakes I wonder?
Thank you VERY much for that research, I am a little iritated by that....

 

If you have 4-wheel drum brakes, you will need a 10# Residual Pressure Valve, one for the front and one for the rear circuit. Usually, the valves are included in the MC ASSY.

See ILL-




For a DRUM/DRUM MC, there will be one in each outlet port. No residual valve(s), spongy brake pedal.

 

This MC has been frequently mentioned in threads on here, it is for a 68 Mustang with drum/drum brakes: https://www.napaonline.com/en/p/NMAM2036

The front port is the one furthest from the mounting flange, I don't think they meant the port for the front brakes. Now that I look at that question again, I'm not sure they are saying the other port doesn't have an RPV; the guy asked about the front port, so that is what they answered. Look in your ports, should look the same for drum/drum.

 

Yes I examined them closely before it was installed, they did look the same and there appeared to be no rubber thing that could possibly be pulled out of the tiny hole.

 

The front outlet is for the rear brake circuit.

DRUM/DRUM MC Ill shows Residual Pressure Valves as 2004 (incl in MC Overhaul kit -

 

Other than the fact that it's gonna cost $40 and an hour of work/bleeding brakes, I think I'm gonna try installing them.