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need answer to earlier question, master cylinder

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by big d, Sep 7, 2002.

  1. big d

    big d 1/2 ton status

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    so can a guy swap out the a 70's 80's cast iron master cylinder to the newer plastic type ? and if one can, is there any problems to be concerned with or is it a direct bolt in ? thanks. /forums/images/icons/grin.gif
     
  2. outlaw612

    outlaw612 1/2 ton status

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    Make sure the brake line line ports have the same thread as the old MC.
     
  3. big d

    big d 1/2 ton status

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    ttt
     
  4. Resurrection_Joe

    Resurrection_Joe 1 ton status

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    I'd really love to knwo which ones are interchangeable too, as I apparently have a 1978 truck with a 85 1/2 ton front clip, and the original builder said the MC was from an 85? Is there a way i can take it off and measure it, or pull a casting number or soemthing? Thanks!
     
  5. dremu

    dremu Officious Thread Derailer Premium Member

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    The new style master is a drop-in ... sort of.

    You gotta replace the booster at the same time as the master cylinder, as they are not interchangeable.

    I just put an 85-91 (plastic tank) master, with an 85-91 booster, on my '77 Chalet as part of a brake overhaul. My guru (AZBlazer) swears by this upgrade, as the newer master has a much bigger bore (same linear pressure from pedal makes much more fluid move, at least, that's the idea.)

    The old-style booster does NOT fit the new plastic tank master. I tried.

    The connections must be reversed (easy to do, just wiggle the brake lines around), but are threaded the same and basically, the booster-master combo is a bolt-in.

    I did hafta buy two 10mm nuts as my new (reman) booster didn't come with them and of course my old booster had SAE nuts.

    I also replaced rotors, hoses, pads, calipers, shoes, wheel cylinders ... so I can't tell you what just the master/booster will do, but that Chalet STOPS now, locks all four and skids on command, which is much better than it was, and impressive given the weight and front/rear ratio of the camper.

    -- A
     
  6. big d

    big d 1/2 ton status

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    thank you very much. i hope the other guy gets this info also. when you mentioed switching lines, this means you moved the line that goes in the back up front and visa-versa ? im surprised they reach w/o bending. well thanks for the info. i should be able to find those parts at any salvage yard. thanks once again.
     
  7. Resurrection_Joe

    Resurrection_Joe 1 ton status

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    So the cutoff year on interchange is 1985? Crap!
     
  8. dremu

    dremu Officious Thread Derailer Premium Member

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    switching lines: yup, front-to-back are reversed. On my 70's trucks anwyay, there's a coil of extra there, so there's lots and lots of play to switch em around; the lines don't even rub or anything.

    Yeah, boneyard woulda been cheaper; I was having braking problems with the Chalet (what, 900# extra on a Blazer and it stops funny? Go figure!) so I bought all new, wanted to get her to STOP, at least until I have her insured LOL!

    RJ, I believe the 1985+ is the plastic two-tub, and I know that 1974-1977 use the metal cast jobbie, but I don't know about years inbetween, sorry.

    -- A
     

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