master cylinder upgrade?

Discussion in 'The whoa and the sway.' started by Esasky's85GN, May 10, 2018.

  1. Esasky's85GN

    Esasky's85GN Car Poor!

    Hey guys,

    Did a disc brake conversion on my 72 last summer. Planning on doing rear disc conversion on it this summer.

    Any ideas on a better master cylinder that can be used for our cars when I go full disk?

    Still have the stock 4-wheel drum MC on it right now. Planning on converting to a 50/50 prop valve when I do the rear disc.

    Didn't know if anyone used a newer GM MC on these cars with a bigger bore to increase fluid volume.

    Thanks in advance.

  2. knucklebusted

    knucklebusted Well-Known Member

    I'm surprised it will stop with the old master from 4wheel drums. I didn't think they had enough fluid volume to work!

    I called inline tube and ordered a disc/disc master and swapped it on with little or no issues. You'd be hard pressed to tell mine has 4wheel discs from under the hood or by looking at it with Buick type wheels but it sure stops faster.

    I don't even had a proportioning valve plumbed and it stops really well. With a hard panic stop it will just barely lock the rears before the fronts. I'd bet money it will stop as good as any car with ABS.

    I'm debating a 4Wheel disc conversion to my 71 GS. What kit are you planning to use for the rear discs?
  3. Esasky's85GN

    Esasky's85GN Car Poor!


    It stops but not as good as I would like it to with that elephant motor in it. :)

    Do you happen to remember which master you ordered?

    I actually had Scarebird brakes custom make me rear brackets that would like me use Chevy Citation front calipers along with Chevy S-10 blazer rear rotors.
  4. knucklebusted

    knucklebusted Well-Known Member

    I do not but I called and talked to them. They sent me that appropriate one. It looks like a stock 70 master with the round edged top. Probably a Corvette model.
  5. Esasky's85GN

    Esasky's85GN Car Poor!

    Hmm. if its a Corvette master, I would think the bore would be 1-1/8". I didn't think you could bolt a bigger bore master on without changing the booster to match.
  6. knucklebusted

    knucklebusted Well-Known Member

    I'm not 100% sure. I just know I called them and needed a disc/disc master and they shipped me one that worked.
  7. Esasky's85GN

    Esasky's85GN Car Poor!

    Cool. I'll have to give them a shout. Thanks so much!

    And you said you are not running a proportioning valve?
  8. knucklebusted

    knucklebusted Well-Known Member

    On second thought, it may have been Right Stuff I got the master cylinder from. It was their brake kit for the rear discs. Pretty sure it was them.

    Not currently. I am just using the factory 70 distribution block. I removed the old hold-off valve when I went 4wheel disc and bought an aftermarket separate proportioning valve I had planned to plumb in but it works very well without it. It stops so much better and a panic stop is much harder to induce lockup than it was before because discs don't self energize like a drum brake will.
  9. Esasky's85GN

    Esasky's85GN Car Poor!


    Ok. I have used their poroducts before. I also found a company that actually offers the MC with the prop valve attached to the side of the MC for our cars. May go that route.

    I haven't been under my 72 to see if there is a stock distribution block. I would assume that there is; at least for the front brakes being it was originally 4 wheel drum.

    When I did my front disk conversion, I left the stock MC in. Figured being that its a 50/50 MC fluid distribution, that it would be good enough for now. Car stops, but not as well as I would like.

    I did also ponder just doing the rear disc conversion and see how the stock MC works.

    I will definitely look into the right stuff MC as well!


Share This Page