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Technical Brake issues AV8

Discussion in 'Traditional Hot Rods' started by Richard Reed, Jul 12, 2020.

  1. Richard Reed
    Joined: Jun 17, 2016
    Posts: 175

    Richard Reed
    Member
    from Maine

    Having a problem getting a firm brake pedal. I have a dual compartment 67` mustang MC mounted on the frame, all 40` ford brake parts. Have a 10lb residual valve for the rear brakes(have ordered one for the front). Have bench bleed the MC twice and the lines 3 times. The brakes are grabbing but the peddle travels 3 to 4 inches before it does grab and it is only 2 inches from the floor boards. Any idea how I can get the peddle to grab sooner?
     
  2. tinkirk
    Joined: Jan 16, 2017
    Posts: 111

    tinkirk

    Maybe another R valve to the front also, anyway that's what i have on mine, i struggled with mine and kept trying to get all the air out of the system but my MC is lower than the wheel cly. Good luck


    Sent from my iPhone using Tapatalk
     
  3. J. A. Miller
    Joined: Dec 30, 2010
    Posts: 1,729

    J. A. Miller
    ALLIANCE MEMBER
    from Central NY

    Do you have the shoes adjusted properly?
     
    ClarkH likes this.
  4. 4ty
    Joined: Dec 11, 2018
    Posts: 212

    4ty

    Why the residual valves?? Is the M/cyl push rod adjusted correctly?? What pedal set-up are you using??
    Paul in CT
     

  5. alchemy
    Joined: Sep 27, 2002
    Posts: 17,464

    alchemy
    ALLIANCE MEMBER

    Are the residual valves the good ones (brass from ECI) or cheap aluminum ones? Yes you need a 10 pound valve on each end.

    I second the question, are the shoes adjusted correctly? Are they arched correctly for the drums? Is everything brand new? But, just because everything is new doesn't mean it's good.
     
  6. ClarkH
    Joined: Jul 21, 2010
    Posts: 1,162

    ClarkH
    ALLIANCE MEMBER

    I have '40 ford brakes and a later Ford dual reservoir MC. I initially had the exact same problem you describe. After finding instructions on adjusting these Lockheed brakes properly, the problem went away. The procedure for adjusting '40 brakes is different than later brakes.

    Here are good instructions; they were posted by @Blake 27 in a brake thread last year. It appears they may have originated with @Richard (EV8G). Credit to all--I suspected they've been passed around on the Hamb for a while. Anyway, they helped me, might help you.

    40 brake adjust 1of2.jpg
    40 brake adjust 2of2.jpg
     
    trikejunkie and Tim like this.
  7. Tim
    Joined: Mar 2, 2001
    Posts: 13,150

    Tim
    Member
    from KCMO

    If adjusting them like ^ doesn’t work I wonder if changing the push rod length would help. You could just have a weird pedal ratio?
     
  8. panheadguy
    Joined: Jan 8, 2005
    Posts: 1,040

    panheadguy
    Member
    from S.E. WI

    /\ or the m/c bore is small
     
  9. Richard Reed
    Joined: Jun 17, 2016
    Posts: 175

    Richard Reed
    Member
    from Maine

    Yes, the shoes are adjusted properly using the procedure in the Ford Manual that ClarkH is showing in this post. The push rod is as far in as I can get it. I can`t say that the shoes are adjusted to the drums but are grabbing so that I can not turn the drum while someone is pushing on the brake pedal. I had the drums turned down even though they are new. The only thing that is not new are the adjusters( but were in excellent condition. The residual valves are aluminum from Speedway Motors. The MC is a 67` Mustang dual chamber rebuilt.
     
  10. alchemy
    Joined: Sep 27, 2002
    Posts: 17,464

    alchemy
    ALLIANCE MEMBER

    You said you are using all 40 parts. This means a 40 pedal and mount too?

    Have you pulled a drum off to see the wear pattern on the shoes? Is it wearing over the whole shoe surface?
     
  11. Tim
    Joined: Mar 2, 2001
    Posts: 13,150

    Tim
    Member
    from KCMO

    Does it make any difference or feel any different if you pump the pedal while trying to stop?

    does it feel the same at all wheels?
     
  12. Richard Reed
    Joined: Jun 17, 2016
    Posts: 175

    Richard Reed
    Member
    from Maine

    The pedals are Model A mounted on an adapter kit from Clings Aftermarket parts. The push rod is part Mustang with an extension welded on to reach the brake pedal. There is a 3 hole piece welded to the bottom of the brake pedal to attach the clevis on the end of the threaded push rod. The car is not on the road. Still going thru my to do list to make that happen and this is on the list. If I pump the brake I get a slightly better pedal.
     
  13. 67L36Driver
    Joined: Jun 1, 2020
    Posts: 76

    67L36Driver

    Have you inadvertently limited the master cylinder to a too short of a stroke?

    Asking for a friend....................
     
    Last edited: Jul 12, 2020
  14. alchemy
    Joined: Sep 27, 2002
    Posts: 17,464

    alchemy
    ALLIANCE MEMBER

    Sounds like the three hole piece on the end of your pedal is adjustable to get different ratios. Maybe you should try a ratio fairly close to 6:1. That's the standard for manual brakes.

    And, it sounds like, from your description, the plunger rod is kinda hokey? You say it's adjusted as far as possible. Is it enough? I'm not picturing it in my head, except for a welded-together conglomeration that's might not be serving the purpose.

    Please don't take my questions as an insult. But, we've seen plenty of these type of questions that turn out to be major scares when the photos of the parts show up. We have no idea how good a fabricator you are, or how experienced you are in the old Ford world. I really am trying to help.
     
    67L36Driver likes this.
  15. jaracer
    Joined: Oct 4, 2008
    Posts: 1,316

    jaracer
    Member

    If the brakes are out of adjustment, the pedal should come up if you pump it.
     
  16. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 4,977

    sloppy jalopies
    Member

    had the same problem with my brakes... there is a threaded "plunger ?" between the booster and mc...
    very precise, had to adjust it a quarter turn at a time...
    it is better but I like 1/2" of free play then brakes... got about an inch now...
    good brakes though...
     
  17. Richard Reed
    Joined: Jun 17, 2016
    Posts: 175

    Richard Reed
    Member
    from Maine

    Thank you Alchemy for your honesty. Ok, I`am not sure how to get that 6:1 ratio but will explain how I adjusted the pedal. I pulled the pedal back up from the floorboard as far as possible, tied it off and adjusted the clevis until it lined up with the bottom hole in the piece welded to the bottom of the pedal. The push rod is now all the way into the MC before it actuates the MC piston. Now if I depress the pedal I do not have any resistance for about 3 inches(just about the length of the travel of the MC piston) then I get a firm pedal about 2 inches from the floor. I am going to have the shoes arched this week and see what happens. Oh, Smitty, I haven`t forgotten you and the spring pac that I need to return.
     
  18. 4ty
    Joined: Dec 11, 2018
    Posts: 212

    4ty

    You could also try contacting Cling's, I believe Bert's in Denver bought Cling's a few years ago. Bert's is a great vendor and should be able to help you. There's a lot of the Cling's setups out there.
    Paul in CT
     
  19. Nailhead-13
    Joined: Dec 5, 2017
    Posts: 11

    Nailhead-13
    ALLIANCE MEMBER

    Did re arching your shoes resolve you brake problem in the end? I have a similar issue with my set up.
     

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