Master Cylinder question.......

Discussion in 'Technical' started by mrcomet, Mar 23, 2009.

  1. mrcomet

    mrcomet Member

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    Hello all,

    I have a 71 Comet that has a Front Disc\Rear Drum brake set-up. The master cylinder on the car is a drum\drum unit. I want to swith out to a disc\drum unit but am having problems finding one. There is a disc\drum unti for a 74 Comet but it is a 15/16 bore instread of a 1 inch bore. It comes with a push rod. Would I be abel to use this one with the new push rod.

    I have heard that a 67-72 Mustang master cylinder will work if it has the 1 inch bore. Does that sound right?

    Please help!!:banghead:
     
    mrcomet, Mar 23, 2009
    #1
  2. 71gold

    71gold Frank Cooper Supporting Member

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    the '74 will be fine...it will be the stock MC for your app.

    :yup:
     
    71gold, Mar 23, 2009
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  3. TUK101

    TUK101 Member

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    This is good to know, I have been wondering about this myself.
     
    TUK101, Mar 23, 2009
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  4. darren

    darren Member

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    I think the pushrod is too long and gives a high brake pedal. My first car had this issue. I think you can switch the rod with your old drum master. Can someone answer that push rod issue? I'm not 100% on that one.
     
    darren, Mar 23, 2009
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  5. 72CometGT

    72CometGT Member

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    I switched to that MC and it did make my brake pedal sit much higher up. I haven't figured out how to fix it yet, I'm thinking about cutting the pushrod and welding it back shorter. A new MC isn't that expensive, I'm also considered just buying one with the right length pushrod...I'd like to know what others used to keep the pedal at the right height.
     
    72CometGT, Mar 23, 2009
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  6. RASelkirk

    RASelkirk Retired!

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    I swapped back to my old drum-drum PR, the 1/4" shorter length made 2" difference in pedal height.

    Russ
     
    RASelkirk, Mar 23, 2009
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  7. darren

    darren Member

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    Can we swap rods from master to master? I cant remember how they are put together.
     
    darren, Mar 23, 2009
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  8. Dave B

    Dave B I like Mavericks!

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    When you buy a 74 Disc/Drum master cylinder, most will come with 2 different length pushrods, because the same master is used on Mustangs (and way more popular). If it doesn't use the one on the Drum/Drum master, it will be the correct height.
    http://mmb.maverick.to/showthread.php?t=50958
     
    Dave B, Mar 23, 2009
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  9. mrcomet

    mrcomet Member

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    Does the pushrod have anything to do with the bore size. Sounds like I can use the original pushrod from the 1 inch bore drum\drum matser cylinder on the 15/16 inch bore mater cylinder.

    Does that sound correct?

    What is the relation of the pushrod to the bore size??
     
    mrcomet, Mar 24, 2009
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  10. rthomas771

    rthomas771 Member

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    The push rod length has to do with the distance between the pedal and master cylinder and nothing to do with the size of the bore. The push rod need to only touch the master and not put any pressure until you press the pedal
     
    rthomas771, Mar 24, 2009
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  11. RASelkirk

    RASelkirk Retired!

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    There's a small 3-cornered snap-ring type clip that holds it in place, a sharp yank will dislodge it.

    The pushrod has nothing to do with bore size, it's only job is connecting and transferring the pedal motion to the piston. However, the length of the PR will set the pedal's initial height.

    Russ
     
    RASelkirk, Mar 24, 2009
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