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Hot Rods Brake issues

Discussion in 'The Hokey Ass Message Board' started by Daves 48 Special, Nov 1, 2012.

  1. Daves 48 Special
    Joined: Mar 30, 2009
    Posts: 76

    Daves 48 Special
    Member

    Got a 48 Plymouth with a camaro clip under it adding brake booster to the car anyone tell me what is the correct rod travel for the brake booster that goes into master .
    Brake booster and master is from a 78 ford mustang 2 .
    The issue is can't get a hard pedal thinking rod isn't traveling far enough into master cylinder .
    Everything is new through brake system if that helps
     
  2. joee
    Joined: Oct 9, 2009
    Posts: 474

    joee
    Member

    sounds like you;ve still got air in the lines.....did you bleed the new mc ?
     
  3. Daves 48 Special
    Joined: Mar 30, 2009
    Posts: 76

    Daves 48 Special
    Member

    Did bressure bleed even gravity bleed still no stiff ness on pedal
     
  4. Daves 48 Special
    Joined: Mar 30, 2009
    Posts: 76

    Daves 48 Special
    Member

    Thinking the rod travel is off it only travels 1/2 in past booster shouldnt it be aleast 11/2 to 2"
     

  5. Daves 48 Special
    Joined: Mar 30, 2009
    Posts: 76

    Daves 48 Special
    Member

    Anyone have any ideas help please
     
  6. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,757

    V8 Bob
    ALLIANCE MEMBER

    Your pedal travel/ratio is suspect. With no vacuum assist, the pedal should be able to full stroke the master before bottoming out on the floor or firewall.
    The clearance between the master primary piston and the booster push rod should be .040", checked with about 20"HG in the booster.
    Keep in mind the Mustang 11 master has a 15/16" bore, and will need more pedal travel than larger bores. :)
     
    Last edited: Nov 1, 2012
  7. JZACK
    Joined: Nov 28, 2009
    Posts: 50

    JZACK
    Member

    was the matster bench bled before you hooked up your lines?
     
  8. Daves 48 Special
    Joined: Mar 30, 2009
    Posts: 76

    Daves 48 Special
    Member

    Bob thanks I'll check the travel again with nothing connected I should be able to check rod travel by hand and adjust my rod pedal according correct
     
  9. Daves 48 Special
    Joined: Mar 30, 2009
    Posts: 76

    Daves 48 Special
    Member

    It was bled on bench
     
  10. I don't know exactly, but 1/2" isn't anywhere near enough.
     
  11. Daves 48 Special
    Joined: Mar 30, 2009
    Posts: 76

    Daves 48 Special
    Member

    That's my thoughts .
     
  12. Dane
    Joined: May 6, 2010
    Posts: 1,351

    Dane
    Member
    from Soquel, CA

    Good info. A 15/16" mc bore MC needs at least a 1" stroke in my experience, especially if you're running the common large piston GM calipers. I have used the large GM calipers with a 7/8" MC bore, but it had a 1.1" stroke available. The larger the caliper bores the more fluid (stroke) it takes to fill them when shoving the piston and pad against the rotor.

    I would plug the outputs of the master cylinder and see if you get a hard pedal without much pedal travel. If not then you still have air in the master or it's no good. If you get a hard pedal with the outputs plugged, check the vacuum assist by pumping the pedal 10 times with the engine off and lightly hold the pedal down on the last stroke and start the engine. You will feel the pedal drop a bit if the booster is working.

    You can check the booster to MC piston gap by putting clay on the MC piston and then bolt it to the booster. Remove the MC and check the clay depth.
     

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