GM Power brake booster spec

Discussion in '1970 - 1973 Specific' started by 67johnny, Sep 17, 2021.

  1. 67johnny

    67johnny Veteran Member

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    Hey all!
    Didnt get much traction on this over in the brake section so thought I would give it a go here!
    The off-shore booster I was given has a non adjustable master cylinder apply pin that appears to be 2 and 9/16 long
    (including nub on inside end of booster).
    Whats the factory one measure up at?
    I dont have one of those H shaped adjuster tools.
    Have had issues before with brake drag.
    Compensating port was covered I believe.
    Dont need that again!
    So stupid they wont make them adjustable like back in the day.
    Looks like another case of off-shore close, counts and the lowest price is the law.
    Just another need to know deal.
    Any help appreciated!
     
  2. berg2695

    berg2695 Veteran Member

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    I was in the same boat recently so I stuck a small wad of Silly Putty in the master before bolting it up. When I unbolted it, it told me I needed to put a shim between the master and the booster to get the desired clearance. (.020" clearance I think. I can't remember for sure off hand.) I was using factory parts but was bolting a modified '77 booster to a '81 master. I cut a shim out of sheet metal that matched the base of the master. I figured washers wouldn't cut it.
     
  3. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    I had to shim one of those pretty repop boosters too.
    (Brakes wouldn’t fully release and we’re VERY hot within a couple of miles.)

    I used stainless steel washers but the diaphragm failed in a couple of years so I went back to my original booster, which had been painted.
     
  4. 67johnny

    67johnny Veteran Member

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    Last edited: Sep 24, 2021
    berg2695 likes this.

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