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dual brake master cylinder info

1K views 7 replies 4 participants last post by  gerry rautenbach 
#1 ·
i got a dual master cylinder and want to fit it to a 64 buick .i have allready fitted disc brakes (it originally had drums) the cylinder i have has a small reservoir and a bigger one. also the fittings for the pipes are different.does the bigger one of the reservoirs go to the back or front?
 
#2 ·
The larger reservoir feeds the FRONT brakes. Use 3/16" lines for the front, 1/4" for the back. I assume you have a proportioning valve?

Note that GM used non-standard threads on some of the flare nuts to prevent incorrect connections on the assembly line. You can buy adapters or these special flare nuts at auto part stores like NAPA and Auto Zone. Don't expect the kid behind the counter to have any idea what you are talking about. You'll need to go through the drawers of fittings in the back of the store yourself.
 
#3 ·
master cylinder info

thanks for info .the larger reservoir is located furthest from the mounting onto the booster ? so when you depress the pedal the rear piston will actually work first? i will have to connect a proportioning valve or the block that connects all the pipes .(front and rear) as i live in good ol' south africa i will have a problem with the fittings as over here everything is METRIC and we do have problems finding Imp. fittings
 
#4 ·
thanks for info .the larger reservoir is located furthest from the mounting onto the booster ? so when you depress the pedal the rear piston will actually work first?
This is a hydraulic system. Brake fluid between the two pistons equalizes the pressure in both simultaneously. This is how hundreds of millions of cars currently on the road are built.

i will have to connect a proportioning valve or the block that connects all the pipes .(front and rear) as i live in good ol' south africa i will have a problem with the fittings as over here everything is METRIC and we do have problems finding Imp. fittings
All the on-line speed shops (Summit Racing, Speedway Motors) as well as the aftermarket brake line companies (Inline Tube, Classic Tube, Right Stuff) sell these fittings in both steel and stainless. Overseas shipping may be expensive.
 
#5 ·
Contact Southside Brake and Clutch in Tacoma Washington, USA for the fittings, proportioning valve and check valves you will need. (253) 473-1433

As stated previously, the large reservoir is for the disc brake axle, the small for the drums. You will need to check to see if there is a residual pressure check valve in the master cylinder for the drum brake axle, if not you will need to add one inline (10lb). Remove the combination valve currently installed on the car and toss it. It is for drum brakes and will not function properly with a disc/drum system.

Summary...Install an adjustable proportioning valve in the original rear line (use the stock lines if they are in good shape, and a 3/16" line will be fine for the rear brakes, a 1/4" line is not necessary but it won't hurt anything if you want to put one in). Make sure to have a 10lb residual pressure check valve in the line to the drum brakes. Put in a "T" fitting to tie the front brake lines together and connect to the large reservoir on the master and you will be ready to test the system and begin the adjustment process for the proportioning valve.

Regards,

Andy
 
#7 ·
1/4" lines are not necessary and will offer no advantage. When the reservoir is topped out and the brakes properly bled, it doesn’t matter what size the brake lines are. It is the transfer of hydraulic pressure that matters not capacity of fluid in the lines.

Vince
 
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