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    Results 1 to 6 of 6
    1. #1
      Join Date
      Nov 2010
      Location
      Ventura County CA
      Posts
      556
      Country Flag: United States

      Mismatched brake system okay temporarily?

      I am currently installing "LS1" rear disc brakes (12" rotors) on my '70 Nova. The car has a stock disc/drum system with 1-1/8" master, 11" booster and 11" rotors up front. Currently I don't have the budget yet to upgrade the front brakes or the master/booster. I would like to get back to driving the car and update the front brakes to C6 Z51 at the end of the year. Can I run a mismatched system in the meantime?

      My plan is to remove the residual valve from the rear port on the master, eliminate the hold-off valve installed on the front system, and re-plumb from the distribution block back, adding a Wilwood 260-10922 adjustable proportioning valve to take bias off the rear.

      Will I have enough adjustment in the proportioning valve to safely bias this system? Are there any other things I need to change to get this working? I understand the disc/drum master will not have a large enough reservoir to accommodate pad wear, but will it be okay if I just keep an eye on the fluid level?

      Thank you for any advice / experience!
      Clint

      Update The mismatched system works fine. See post #6
      Clint - '70 Nova "restomod" cruiser & autocross family car

    2. #2
      Join Date
      Jun 2006
      Location
      Katy,TX
      Posts
      1,678
      MC may not be that off the 79-80 TAs with 4 WD used basically the same MC as the disc drum cars less RP valve. You planning on wearing out the rears that much?

      Adjustable prop valve should get you there.
      1978 Black Trans Am 455 Edelbrock heads [email protected] through mufflers on pump gas
      1981 Trans Am 400 stock type motor
      79 Camaro getting a 500" 695 hp IA2 Pontiac motor
      1965 GTO project car
      470ci/Chevy dual quad 409 604 HP 64 Impala SS project
      2004 Pulse Red GTO

    3. #3
      Join Date
      Nov 2010
      Location
      Ventura County CA
      Posts
      556
      Country Flag: United States
      I don't expect to put a lot of wear on the rear before upgrading the front. I'll probably put <1k miles on the car this year and maybe two or three autocross events. From what I've read the rear reservoir on the disc/disc masters is larger than the disc/drum masters to account for pad wear. Drums don't need the extra volume because they mechanically adjust as the shoes wear.
      Clint - '70 Nova "restomod" cruiser & autocross family car

    4. #4
      Join Date
      Jun 2006
      Location
      Katy,TX
      Posts
      1,678
      The fronts do most of the work. I'd bet any rear MC will work esp short term. I'd wait until you get the big system and then get one for that system.
      1978 Black Trans Am 455 Edelbrock heads [email protected] through mufflers on pump gas
      1981 Trans Am 400 stock type motor
      79 Camaro getting a 500" 695 hp IA2 Pontiac motor
      1965 GTO project car
      470ci/Chevy dual quad 409 604 HP 64 Impala SS project
      2004 Pulse Red GTO

    5. #5
      Join Date
      Nov 2010
      Location
      Ventura County CA
      Posts
      556
      Country Flag: United States
      Thanks for the advice. I'll report back on how it goes.

      Clint - '70 Nova "restomod" cruiser & autocross family car

    6. #6
      Join Date
      Nov 2010
      Location
      Ventura County CA
      Posts
      556
      Country Flag: United States
      Thanks again for the advice. I got the car back together with the mismatched brakes as described in the first thread. With the proportioning valve adjusted to center as a starting point (i.e. half way between full open and full close), the fronts still lock before the rear and braking at this adjustment feels pretty good; I am sure it will get better when I optimize the adjustment.

      I found there was no residual pressure valve installed in the rear port of my disc/drum master. It was a remanufactured master so perhaps they left it out.

      BEFORE



      AFTER

      Clint - '70 Nova "restomod" cruiser & autocross family car





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