Using a disc brake master cylinder in a drume brake car.

Brakes for your Classic Mopar

  1. RichieDart

    RichieDart Member

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    Is there a problem with using a disc/drum brake MC in an all drum brake car? Specifically a '72 Scamp with 9 in drums all around. I have a few A body disc brake MC's sitting on my shelf. Some one told me that brakes will work better this way. All other components (lines, hoses,wheel cyl.) are stock & in good working order.
     
  2. Murray

    Murray FABO Gold Member FABO Gold Member

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    This would work except for the fact that a disc brake system uses no residual check valve in the M/C. Without it a drum brake system will work worse.
     
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    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      ^^This, and you can buy inline residual valves "aftermarket" You may be able to get by without them
       
    • Murray

      Murray FABO Gold Member FABO Gold Member

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      The purpose of a residual check valve is to retain a small amount of line pressure, about 2-3lbs. Without it, pedal travel is increased to make up the difference. Disc brakes use no such valve as that would not allow the caliper piston to retract. Often this "residual check valve " is a small rubber "flapper valve" under the line fitting in the M/C.
       
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      • Oldmanmopar

        Oldmanmopar Going left turning right FABO Gold Member

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        Put the correct master on the car and proportioning valve. The disc brake Master holds more fluid so it don't go dry when the pads wear. Don't take a chance.
         
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        • 383Scampman

          383Scampman Well-Known Member

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          So ! You are asking our opinion about an issue , correct ? A correct master cylinder from NAPA is $35.00 exchange . If you are that cheap you don't need our advise . My question to you is : what is your life worth ?
           
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          • RichieDart

            RichieDart Member

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            It is not an issue of $. I was merely asking if it should be done. I have actually seen it done on other '72 scamps with same brake setup. I will purchase the "correct" M/C. Thanks to all for their input.
             
          • RichieDart

            RichieDart Member

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            I am not an auto mechanic. I joined this forum to learn. I have learned a great deal from this site. Now I know a little more about braking systems than I did before.Thank You again.
             
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            • Oldmanmopar

              Oldmanmopar Going left turning right FABO Gold Member

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              Don't take comments personal it will get to you after a while. With disc on the front only, The pressure needed is different from front to rear . If you have 4 wheel disc you can use that proportioning valve for 4 wheel drum, But up grade to a 4 wheel disc plastic reservoir master where the reservoirs are connected so front and rear both have a large capacity of fluid. I too have seen many disc brake cars with drum brake masters. But its really not safe.

              HAPPY NEW YEAR! Welcome to FABO you'll get use to it. Steve
               
              Last edited: Jan 1, 2020
            • maddawg57

              maddawg57 New Member

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              I am running a disc brake master cylinder with a proportioning valve , and drum brakes on my 68 Dart no problems . 9' drums front , Dodge Van drums on a Moser narrowed 8.75 rear. Going to upgrade to the later spindle and A-arm and 11' disc soon.

              00J0J_99m8mY4HuDu_1200x900.jpg
               
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