Hydraulic master cylinder - Firewall flex solved

Manual Transmission & Clutch Discussions

  1. Jason Wenger

    Jason Wenger Active Member

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    IMG_20200819_134818.jpg IMG_20200819_134826.jpg IMG_20200819_134920.jpg IMG_20200830_151208.jpg IMG_20200830_150736.jpg IMG_20200830_150730.jpg IMG_20200830_150725.jpg

    Anything worth doing is worth overdoing.
     
    Last edited: Sep 27, 2020
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    • 19Greg69

      19Greg69 Member

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      Outstanding job!!!!
       
    • MoparMike1974

      MoparMike1974 FABO Gold Member FABO Gold Member

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      Nice solution. The factory power brake setup had two or three braces that went to the firewall and inner fender. I can tell you, without them the master cylinder moves about 1/2" left and right with each pedal push. Wouldnt take long for the firewall to crack.
       
    • moparmat2000

      moparmat2000 FABO Gold Member FABO Gold Member

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      That looks great. I could see you being able to make and sell quite a few of these
       
    • Magnum Valiant

      Magnum Valiant Active Member

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    • Magnum Valiant

      Magnum Valiant Active Member

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      Did you cut a hole for the clutch MC, or was it already there, speedo cable?
       
    • Jason Wenger

      Jason Wenger Active Member

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      Hah! Took me more than a day, all hand work. -- Need to add a photo, the back side required a couple hours of careful slow grinding to match the profile of the firewall. Can't imagine that's quite the same for any two cars in the same year, let alone generically. It'd be tough to produce in bulk.
       
    • Jason Wenger

      Jason Wenger Active Member

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      Yes, used the same hole saw I used to make the hole for the clutch master cylinder in the plate in the bracket. There's about an inch of the master housing that sticks out past the mounting plate, so the hole in the firewall has to be big enough to clear the master and the rubber boot, not just big enough for the pushrod alone. That's another reason I wanted the bracket like this, making so large a hole in the firewall, I wanted it sealed up.

      The firewall there has part of the bend, so it's not a hole through a flat section of firewall, but it's the only place you can do it. I still like this a lot better than putting the clutch master through the firewall hole for the clutch throwout pushrod, which requires the cylinder to be very low, and at a very steep angle and also to interfere with the wheelwell. I couldn't see any way at all to make it fit that way in fact.

      The manufacturer says you want a 6:1 pedal ratio, so that, based on the geometry, requires the centerline of the clutch master to be about an inch lower than the centerline of the brake master. Hence the dogleg shape. Now let's just hope it actually works out.
       
      Last edited: Sep 28, 2020
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      • RustyRatRod

        RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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        Yeah, I imagine that'll do it! Nice work!
         
      • dogbreath

        dogbreath Well-Known Member

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        earl a or early b ??????????
         
      • Tooljunkie

        Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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        Well done! If anything you have shared a solution to a common problem.
         
      • Jason Wenger

        Jason Wenger Active Member

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        '76 Duster
         
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