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Thread: Vacuum Source for Power Brakes & Other Questions

  1. #1
    Join Date
    Jan 2004
    Location
    Oxford, Maryland
    Posts
    33

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    I have read most of the old posts re power brakes and have never seen the answer to this: stock engine, power brakes; what's the best place for vacuum? I suspect I could tie into the egr valve below the carb but am not sure. Second ques.: I'm not satisfied that I have the definitive answer to whether or not I can use a master cylinder from a wagoneer ('80) that has front disc brakes. I pulled the booster and master cylinder from the truck and can use the whole thing if it's safe. HELP? Still would like to get measurements or drawings for brackets for a powersteering pump for the 230. Thanks for all the help.

  2. #2

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    you can. You might have to fiddle w/an aftermarket proportioning valve, which is no big deal.
    **I heart Bump_r **

  3. #3
    Join Date
    Dec 2003
    Location
    West-central Ohio
    Posts
    685

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    egr valve? huh, wha, where, huh?
    "other peoples junk, is something or other" - Militarypotts 02/07/2011

  4. #4

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    Get a cheap, like $22, 1977 non power corvette master and bolt it on your booster. No proportioning valve needed...plenty of fluid moved.
    Big Blocks RULE!

  5. #5

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    whuh? 77 Vettes didn't have power brakes???????????

    prop vave just to keep the rears from locking up, I meant. If he's got the master and booster from a FSJ, fire it up!
    **I heart Bump_r **

  6. #6
    Join Date
    Dec 2003
    Location
    Lone Pine, CA
    Posts
    451

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    You'd be miles ahead to get a drum/drum master cylinder or as Spicer suggested, the disc/disc one. The disc/drum cylinder typically has two different residual pressure valves inside.

    Chris

  7. #7

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    Lucky: I think you might be mistaken on that one. The residual pressure valve, if any, is usually in the factory proportioning valve on the frame. The master cylinders usually just have different sized bores for each piston if memory serves me correctly. I just went out and looked at the setup on the bench, out of a 78 GMC 3/4t truck...
    **I heart Bump_r **

  8. #8
    Join Date
    Jan 2004
    Location
    Oxford, Maryland
    Posts
    33

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    Scratch "EGR": sub "positive crankcase ventilation" valve. I am a "newbie" afterall. LOL

  9. #9
    Join Date
    Dec 2003
    Location
    Lone Pine, CA
    Posts
    451

    Default

    What I've been told/learned is that the RPV is in the master cylinder, usually behind the inverted flare fitting. Drum/drum gets a pair of 10 pounders, disc/drum gets one of each or just a 10 lb on the drum circuit and disc/disc probably gets none.

    According to MasterPower, the "proportioning" valve - actually a combo valve - has 2 functions:
    Metering or holdoff to apply the rears just barely sooner than the fronts to stop straight and level
    Proportioning to control the pressure rise to the rears to keep from locking up.

    Personally I don't like the idea of using an OEM combo valve on anything other than the original application since the brake bias is set up for a specific brake characteristic. With the adjustable ones you can dial in exactly how hard you want the rears to come on.

    Chris

  10. #10

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    Chris: I agree. Custom is better but not as 'easy'. I'm going to go w/manual 4whl disc master and whatever else I need after that.
    **I heart Bump_r **

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