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Technical no brakes! 50' chevy car!

Discussion in 'The Hokey Ass Message Board' started by 49' bomb!, Mar 21, 2017.

  1. 49' bomb!
    Joined: Nov 21, 2016
    Posts: 143

    49' bomb!

    i'll keep this short. I installed a dual master cyl. in place
    of my single one. it's from a 70' mustang, 1"bore. I mounted
    in original location. I plumbed it this way; resvior. closet to
    firewall, goes to front brakes. other resvior. to rear brakes.
    I keep the stock drum brakes all around. there all adjusted
    properly. I have bleed the system several times. I still end
    up with hardly any brake pedal. I know a lot of you guys
    proably have gone thru this? does any body have any good
    ideas. i'am lost?
     
  2. Did you bench bleed first?
     
  3. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 31,179

    Jalopy Joker
    Member

    is 1" bore same as original? is it a drum/drum master cylinder? did you change/adjust rod from MC to brake pedal?
     
  4. Do you have residual valves in line between the master and the brakes? A 1 inch bore will work fine. That is what I have on my 51. Did you modify the original pedal for the new master? Is it an aftermarket pedal assembly? I had a pedal set up that I bought from speedway that had such a bad ratio it would not stop at al . Used all the same hydraulic parts on a Walton fab pedal and it works great.
     

  5. ems customer service
    Joined: Nov 15, 2006
    Posts: 2,634

    ems customer service
    Member

    there is a adjustment between the pedal and master rod plunger to small or to tight makes a difference, also does pump up when you pump the brakes??
     
  6. 49' bomb!
    Joined: Nov 21, 2016
    Posts: 143

    49' bomb!

    thanks for all replies! 1st. did bench bleed with tubes in M.C.
    1" bore is same as orig. I fabricated a mtg. brkt. (couldn't
    spend $200 for one). I do believe I have the right amount
    of rod travel. from what I have been reading I think I need to install
    prop.valve. drum/drum. hopefully this will do it? i'am open to
    any more ideas? thanks to all!!!!
     
  7. You don't need a proportioning valve. You need 10 pound residual valves in line between the brake and the master cylinder, one for the front brake circuit and one for the rear. This will keep the brake fluid from running back from the wheel cylinders to the master cylinder.
     
    poboyross likes this.
  8. poboyross
    Joined: Apr 29, 2009
    Posts: 2,142

    poboyross
    Member
    from West TN

    Nailhead Jason is right. I mounted the same setup but with a power brake booster to my 50 Chevy and thought I could get away without the residual valve. I had a front disk kit so my setup was slightly different, but same principle applies. Make sure you have a drum/drum MC and do those residuals and you should be good to go. I also think the front residual is a 10lb and the rear is more? Don't quote me on that. I think TCI or Walton Fabrication has diagrams up with all the info.


    Sent from my iPhone using The H.A.M.B. mobile app
     
    Nailhead Jason likes this.
  9. 49' bomb!
    Joined: Nov 21, 2016
    Posts: 143

    49' bomb!

    thanks for all the great replies!I'll try to let you guys know the final outcome.
     
  10. BJR
    Joined: Mar 11, 2005
    Posts: 9,817

    BJR
    Member

    Usually disc brakes use a 2 lb residual, drum use a 10 lb residual.
     
    poboyross likes this.
  11. Did you get a mc with or without disc brakes.
     
  12. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,802

    jimmy six
    ALLIANCE MEMBER

    BJR has it. One of the manufacturers makes them in colors. One is red and the other is blue.
     
  13. quicksilverart46
    Joined: Dec 7, 2016
    Posts: 460

    quicksilverart46
    Member

    The master is under the floor board and if the car is lowered the master is below the level of wheel cylinders and calipers so the fluid will run back slightly towards the master. That causes you to lose your pedal pressure. The only way to fix the problem is with the residual valves. 2 pound valve to the disc brakes front and 10 pound residual valve to the rear drum brakes will do the trick.


    Sent from my iPhone using The H.A.M.B. mobile app
     
    poboyross likes this.
  14. 49' bomb!
    Joined: Nov 21, 2016
    Posts: 143

    49' bomb!

    I spoke to a couple professional brake co.they said the master cylinder that I have. 1970 Mustang dual Reservoir.drum to drum. it's supposed to have built-in residual valve. I have not checked that yet? I'm waiting for my aftermarket residual valves.I will install them and go from there.
     
  15. murf 32
    Joined: May 30, 2013
    Posts: 70

    murf 32
    Member

    I just had a similar problem wheel clinders stuck. Might be worth a look. Murf
     
  16. Even if it they say it has them built in you should put them in. It will help with keeping the pedal pressure up. Don't use the cheap ones from speedway, they suck, and always seem to leak. Use the good ones fro Willwood, and you wont have any problems.
     
  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,264

    gimpyshotrods
    ALLIANCE MEMBER

    A quick way to check is to undo the lines and look where they go. The is a cone in in each port where the flare seats. If those cones are made of the same Iron (or whatever the master cylinder body is made of), it does not have residual valves.

    If those cones are brass, sometimes with a hex head, it might have residual valves.

    Shown with one removed, in hand:
    [​IMG]
    The reason I say might is that some master cylinders have brass seats, and no residual valves, some have the residual valves removed, and others are repaired using brass cones during the rebuild process with them.

    You can verify, if you have brass seats, with a paperclip. Straighten it out, and gently press it in the hole in the center. If you feel a little rubbery resistance just past the brass, it has a residual valve. If not, it does not.

    This little duck billed dealy is the residual valve:
    upload_2017-3-24_12-27-4.png

    It, if it is there, is inside the brass cone.
     
  18. 49' bomb!
    Joined: Nov 21, 2016
    Posts: 143

    49' bomb!

     
  19. 49' bomb!
    Joined: Nov 21, 2016
    Posts: 143

    49' bomb!

    thanks for taking pictures! I appreciate all replys!
     

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