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I'm in the process fo putting a 69 mustang dual master cylinder in my 46. The new master has two different size outlets. I need to know which one goes to the front brakes and which one goes to the back.
Thanks
George

Usually bigger resivoir for front or discs. If you don't have discs, still think front is front. They are two sizes so you don't mix up in factory when building the car. AND...Phord parts don't fit Chevy's!!! :p :rolleyes:

Your disc's run 3/16" and the drums run 1/4", so the smaller fitting should probably be for your discs.

PS- don't forget your residuals and proportioning valve.

The bigger resivior goes to the disk brakes. The manual brake master cylinder is backwards from the power brake cylinder. On manual brakes, the rear resivior is for the front brakes and the smaller is for the rear brakes. You can find adapter lines a your local NAPA. They have the bigger metric ends on one side and the standard on the other. If you look at the outlet ports and measure the holes where the fluid comes out, you will see that the line size won't make much difference as the holes are the same size. And once the lines are full, the fluid won't know the difference.
I just went through this on my 37. I ended up with a manual brake 68-72 Mustage cylinder with a 77 Malibu splitter/safety valve and for the rear brakes, a adjustable propotioning valve to limit them. I was having trouble with rear wheel lockup. With the valve in line, I just keep adjusting till the rears quit locking up under a hard stop. If the master cylinder is not any lower than the highest bleader valve, you won't need any other valves. Joe

Au contraire on the valve comment. Disk brakes should have a residual check valve in line between the master and the brake clyinders. This will keep the pads from fully retracting (or even partially retracting) thus keeping the pedal firm. Nothing worse than stomping on the pedal and having the first pump do nothing but push the pads out but not far enough to do anything.

I got discs on my 37 using the the Mustang dual master cylinder.Both chambers on the cylinder are the same size on mine and the chamber closest to the mounting flange is supposed to go the the front brakes. The speed shop where I bought it gave me two special flare nuts to screw into the cylinder, using 3/16 lines front and rear.Some master cylinders have the residual valves built in for the drum brakes.I have read and been told by the street rodders that residual valves on disc brakes are only necessary if the master is below the height of the caliper.Actually disc brakes will work with any type of master cylinder including the stock one.Of course the leverage ratios may be wrong , the master may not pump enough fluid for proper braking and a built in drum brake residual valve may drag the discs excessively.The Mustang cylinder is used a lot because its inexpensive, compact and the piston size is reasonably close.

No residual valve required on disk brakes when master is higher than cylinders? I was told that when the master is below the floor boards that a 2 lb residual back pressure valve should be used for the disk circuit and a 10 lb residual back pressure valve should be used for drums regardless of master cylinder location. Would the 2psi residual valve create excessive pad / disk wear? 2psi is equivalent to about 5 ft of water column . . . brake fluid is lighter than water so 2psi at the pad at rest would be more than 8 - 10 feet of master cylinder height over pads . . . :confused: , I'll stick with the 2 psi residual pressure valve.

Ken ,my 37 truck has a 2 psi for the discs and a 10 psi for the rear drums.If the front wheel is rotated by hand, there is a little drag on pads, maybe slightly more than a newer vehicle, but not excessive .When I did the brakes, the local speed shop said "here, you need these parts to make it work" and also gave me a brake design phamplet from some hot rod parts supplier.I had no prior experience in these swaps and just did everything exactly(well sort of)as the phamplet said.The brakes work just fine, no need for a vacuum booster on my 3000 lb truck

Thanks for all the replys. I'm running drums on front and back so I shouldn't have to worry about a proptioning valve. From what has already been said I'll run the bigger outlet to the front. I'm in the process of building a bracket now. I'll let you know how it turns out.
Thanks!
George

I found this info on a classic Corvette web site. ********************************************************************************************************* Lets make a list of some of the things you will need for your brakes. If your master cylinder is under the floor and you're using a disc drum set-up, you will need to use a 10 lb. Residual valve for the rear drum brakes, and a 2 lb. Residual valve for the front disc brakes, these valves go between the master cylinder and the GM intermediate proportionate valve. Unless you have 4 wheel disc brakes then you need to eliminate the proportionate valve and use two 2-pound residual valves. A 1-inch bore master cylinder will also be needed for your disc/drum set-up. Here are the part numbers for master cylinders. The first one is a F**d master cylinder that exits toward the frame rail and that number is 10-1525. This master cylinder has a large and a small reservoir, the large reservoir is for the front disc brakes. The other master cylinder exits towards your transmission and that number is 10-1371. This master cylinder is a Corvette master cylinder and both reservoirs are the same size. How you tell the front from the back is by the port, the larger port is for the rear brakes. Keep in mind I use the word port and not reservoir. These part numbers should be good at any Carquest, Napa, AutoZone or Advanced Auto parts stores. If you happen to have your master cylinder on the firewall, then you will not need to use residual valves, only the proportionate valve, unless you are using four-wheel disc brakes.------------------------------------------------------------------------------------
Four-wheel disc brakes are a whole other ball game. One, they use 4 calipers, and because they use 4 calipers it takes a lot more brake fluid to operate this type of system. One of the more popular rear ends is the Lincoln Versaille; one because it has calipers and rotors and the other is that it is a 9-inch F**d. One of the problems you will find in using this rear end is that the emergency brake is part of the caliper. The reason that this can be a problem is that most street rodders don?t hook up the emergency brake. Hooking the cables to the emergency brake arm on the caliper is difficult. Usually because the brackets are missing or the street rodders don?t have the correct end for the cables. These calipers have to use the emergency brake to keep them in adjustment. By not using the emergency brake, the brake pads will eventually start to wear in an uneven pattern. This causes loss of stopping power. One of the first things that a customer will ask me is, I have 4 wheel disc brakes, when I first installed them they worked real well, now they have slowly gotten worse. Not hooking up and using the emergency brake, which helps adjust the rear calipers, cause this. Just hooking up the emergency brake will not ensure that the calipers will adjust themselves, you will need to use your emergency brake at all times. Actually, it is recommended when you first install this system you need to pull and release the emergency brake at least 150 times, before using the brakes.-------------
The second problem that arises when using 4 wheel disc brakes is bore size of the master cylinder. Because 4-wheel disc brakes hold so much brake fluid, it takes a bigger bore master cylinder to stop the car. This master cylinder would have a 1-1/8 inch bore. This master cylinder gives you the volume but without using a power booster you don?t have the strength in your leg to stop the car. Some rodders will drop down in bore size to one inch, this will help somewhat in the fact that it makes it easier to stop the car, but the trouble with this is the pedal travel is almost to the floor before the brakes engage.

It is my understanding that the 69 Mustang MC has residuals built in--another reason folks tend to favor it for this application.

Ed