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Technical What dual MC will fit my 1964 Chevy

Discussion in 'The Hokey Ass Message Board' started by slim tempo, Jul 12, 2020.

  1. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    I'm going to upgrade to a dual master cylinder on my "white whale". Any Chevy guys know what MC I should order? In the past, I have converted my 1962 Buick Special MC to a dual Jeep MC.
     
  2. Cincinnati Slim
    Joined: Jun 26, 2007
    Posts: 352

    Cincinnati Slim
    Member
    from Cincy, OH

    Power or manual?
    Before I went to disc, I ordered a 68-70 bel air/impala manual drum master cylinder.



    Sent from my iPhone using H.A.M.B.
     
    Elcohaulic and slim tempo like this.
  3. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    Manual and drum brakes.
     
  4. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 2,218

    Elcohaulic

    I think you will need a 1" bore or smaller.. Power brakes usually have a bigger bore than 1".. Good move by the way!
     

  5. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    I took off the cover of the MC and had my son pump the brakes. Sure enough, bubbles coming up in the MC. Bad seal?
     
  6. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 2,218

    Elcohaulic

    Somewhere in the circuit air is entering. Could be tubing, a loose connection, wheel cyl... The leaks that just pull air are the hardest to find..
     
  7. 1934coupe
    Joined: Feb 22, 2007
    Posts: 4,871

    1934coupe
    Member

    A 67 Chevy fullsize. (Impala etc) with drum brakes. Oh I see it has already been answered.

    Pat
     
  8. saltflats
    Joined: Aug 14, 2007
    Posts: 11,574

    saltflats
    Member
    from Missouri

    Brake Best Select #NMC11421 7/8 inch bore
     
    MO_JUNK likes this.
  9. I match them up as closely to the size and weight on the car, so a '67 Impala is a good match. Avoid those crappy Corvette "style" pieces of crap. I buy most of mine from Rock Auto.
     
    Cosmo49 likes this.
  10. 68 or newer Nova manual master work good
     
    Cosmo49 likes this.
  11. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    I installed a 1969 Impala MC today. Bench bled the MC and connected all the lines as specified by most of the wrenches here on HAMB. Car slows but doesn't stop on a dime, or even stop safely. Checked all connections and bled the brakes again. Same thing. Then I read that the front port is for the front brakes and rear for the rear brakes, I have it opposite. Both reservoirs are the same size. Why does it make a difference? And could that be the reason? Drum brakes all around.
     

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  12. squirrel
    Joined: Sep 23, 2004
    Posts: 52,803

    squirrel
    Member

    What did it do before you changed the master cylinder?

    Are the old and new the same bore size?

    And have you fixed the rest of the brake system, yet?
     
  13. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    Same bore size 1 1/8". New wheel cylinders installed before I got car. 0 miles on them.
     
  14. saltflats
    Joined: Aug 14, 2007
    Posts: 11,574

    saltflats
    Member
    from Missouri

    1 1/8 sounds to big for a manual brake.
     
    Johnny Gee likes this.
  15. squirrel
    Joined: Sep 23, 2004
    Posts: 52,803

    squirrel
    Member

    asking again...
     
  16. jimmy six
    Joined: Mar 21, 2006
    Posts: 12,471

    jimmy six
    ALLIANCE MEMBER

    No bigger than 7/8” bore for a good brake feel with no power. If and when you convert to front disc ( non-power) you will be ready also..
     
  17. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    When it was single circuit, good brakes, stopped well until I lost the brakes last week. Now it slows down with some pressure on pedal but won't stop quickly.
     
  18. I don't know, but surely someone here can answer.
     
  19. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    Original single circuit MC bore was 1 1/8".
     
  20. Expand on this. What's going on with the pedal/feel?
     
  21. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    I have been searching the posts on MC brakes and there are differing opinions on where the lines go, either the front or the rear of the MC.
     
  22. Are there any markings on the m/c? Did you get instructions or look for them online?
     
  23. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    Pedal has pressure, and slows the car but not very quickly. Pedal does not bottom out either. Just slows the car down even when I stomp on it.
     
  24. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    No markings on MC. Remanufactured made in Mexico replacement for 1969 Impala.
     
  25. squirrel
    Joined: Sep 23, 2004
    Posts: 52,803

    squirrel
    Member

    You did some plumbing to fit the new master cylinder, didn't you? Any pictures of that?
     
  26. Have you measured the drums? Out of spec drums won't stop as good.

    Maybe 69s have a proportioning valve?
     
  27. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    No pictures yet. I will take some tomorrow. I did the plumbing after stopping at the parts store for fittings.
     
  28. slim tempo
    Joined: Sep 16, 2010
    Posts: 412

    slim tempo
    Member

    Original had 1/4" out of the single circuit. It still has 1/4" to the front and 3/16" the the rear.
     
  29. 1971BB427
    Joined: Mar 6, 2010
    Posts: 7,806

    1971BB427
    Member
    from Oregon

    Shouldn't matter which is front, and which is back in a drum-drum setup, where the master is equal reservoir size front-back. I'd go back to the brake system to check all 4 drums, brake shoes, and make sure it's all clean, no brake fluid from your previous problem on shoes, and drums aren't glazed over, and need turning.
    Once that's all done, then be sure to check you brake pivot point on the pedal! It needs to be in the hole closest to the pivot point for proper leverage.
     
    Cosmo49 likes this.

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