What is going to happen when I remove the master cylinder?

Brakes for your Classic Mopar

  1. gdizzle

    gdizzle Well-Known Member

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    In my 66 dart, original drum brakes, single cup MC. Getting ready to swap it all over to disc so i bought a new MC with the dual cup, small bore, manual. It is my understanding this new MC is bolt on, and reuses the brake push rod. So is it really, jst remove the old MC, and then bolt up the new MC and it will connect to the old Push rod?? Or am I also removing the push rod??
    thanks for any help.
    and yes I am running new brake lines .
     
  2. Steven190

    Steven190 FABO Gold Member FABO Gold Member

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    The only thing that may need when you replace the master cylinder is that the push rod maybe short. I know that it is a pain sometimes but after you replace the master cylinder if there is some free pedal travel, then you will have to get an adjustable rod and make it longer than your stock one. It should come out by a bolt on the pedal, just hard to get to sometimes. Good Luck
     
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    • abodyjoe

      abodyjoe Well-Known Member

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      you may need the pushrod for a 73-up system.. i thought when i removed the single pot master cyl form my 64 many years ago that it was a different rod set up.
       
    • valiantwagonguy

      valiantwagonguy FABO Gold Member FABO Gold Member

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      in a 66 A the push rod is no problem.I have done this swap more times than I can count and never had any issue with the push rod. If you are going to disc brakes from drum you had better make sure the master you are going to use is for disc brakes. They are different for disc and drum. You will also need a proportioning valve and the correct metering block because now you are adding seperate lines to feed the front and rear brakes .
       
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      • Syleng1

        Syleng1 Karma is real and Life is short... FABO Gold Member

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        Just to add here for somebody that may not know the difference.
        Disk /drum master cylinder has one resivour larger than the other. Larger is disk requires more fluid than the drum 1/2.

        Drum/ drum master the resivour s are the same size as the wheel cylinders are typically needing close to the same amount of fluid. Also I learned because brake fluid gets hot and disks get even hotter. The extra fluid is also a basic type radiator. Also the larger qty of fluid is a safety margin if you lost brakes you have so many stops before you ran out of brake fluid.
        Technically the proportioning valve has a valve that detect the lack of pressure from the leak and shuts down that pressure.

        It’s not so complicated. Do more reading thru the search as a lot of conversions have been discussed on this board about this matter. Education is only a “click”away. Good luck.
        Joe
         
      • valiantwagonguy

        valiantwagonguy FABO Gold Member FABO Gold Member

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        The metering block is what detects low pressure the proportioning valve restricts pressure to the rear wheels so they don't lock up in a disc brake application which is why it's only used in disc brake cars from the factory.some people add them to dial in their brakes too and you can even get aftermarket adjustable ones . Drum brake cars all have metering blocks . With the disc brakes you may only have a proportioning valve so you need to research this But the block that the feed lines from the master to the front and rear lines on a drum brake system is a metering block which is why it has a fitting for the idiot light wire on it.Basically it's a ground switch that makes contact when you lose pressure in either side of the block making the light come on.
         
        Last edited: Feb 12, 2019
      • gdizzle

        gdizzle Well-Known Member

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        †hanks for the info. I plan on using a new Adj porportioning valve along with the old meter block and block one of the outlets. OK so I removed the old MC, and didnt realize I had to first detach the push rod from the pedal. Ok done. Then pulled it off carefully and pushed it into the new MC. However there is no way to attach the old spring/booty panel, as seen in this picture of the old push rod put onto the new MC and the plate sitting near it. Is this acceptable? Also does anyone know the outlet size on the old metering block going to the rear brakes? The plug I bought is 7/16 and is too big. IMG_3700 2.jpg
         
      • valiantwagonguy

        valiantwagonguy FABO Gold Member FABO Gold Member

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        Take it with you to the store where you are buying the plug and get the correct part for what you are trying to do. It may have to be something special to mate with the small cone inside the block that the brake line fits over. You can't just thread something in there with a flat bottom.The fluid could leak past the threads if you do that.
         
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