LS1 rear brake upgrade

Discussion in 'Suspension, Steering, Brake & Wheel Topics' started by screamindemon, Jun 28, 2020.

  1. screamindemon

    screamindemon Veteran Member

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    Hi so I’ve read pretty much every article on upgrading your rear brakes but there was a couple things that I Want to try that’s different. The reason is I have the 1981 aluminum master cylinder with the plastic reservoir and Don’t really wanna put in one of the cast iron units
    I’ve read that if there’s a residual valve in the master cylinder for the rear brake system that it needs to be removed and you can continue to use the same master cylinder for rear disk.
    I’ve also read that the combination valve only needs to have the front metering section removed and the rest of the block will still work with the rear disc brakes.
    In conclusion I would like to say that I know this topic has been beat to death by you guys but has anyone tried this yet?
     
  2. Skip Fix

    Skip Fix Veteran Member

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    Pretty sure the aluminum ones do not have a residual pressure valve in them. If the flair insert is brass with a springy black piece behind it it does.
     
  3. screamindemon

    screamindemon Veteran Member

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    I was under the impression that all drum brake systems use a 10# residual valve to keep pressure on the system. Either in the master or the combo valve or possibly an inline one. So I’ll have to track it down!
    Sometimes I read that you absolutely must use a disk/disk master for 4 wheel disk application and other times read the only thing that is different is the residual valve and the size of the fluid bowls (which doesn’t seem to be the case with this one) so you remove that and now you have a disk/disk master cylinder.
     
    Last edited: Jun 29, 2020
  4. ErikNORCAL

    ErikNORCAL Veteran Member

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    I have a cast iron unit with stepped ports and an adjustable valve, info on here somewhere. haven’t really tested it out fully, seems fine. but one thing to not overlook is the original rear brake line is larger. Want to say 1/4 but you’ll more than likely replace it anyways.
     
  5. screamindemon

    screamindemon Veteran Member

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    Ill be honest, I wasn’t planning on changing the rear line. Not really sure how that would make a difference?
     
  6. Zee

    Zee Veteran Member

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    That rear brake line issue can bite you in the butt. I just finished mine today as I had to fit it with my welded SFCs which was a bit of a pain. I thought I would just add the LS1 rear discs, get the right fittings on my brake hoses to adapt them to the stock 3/16 lines to the calipers, cut, reflare and be done with it. Until I went to install my Wilwood adjustable prop valve which uses a 3/16 line to the rear brakes. Then I could not find an adapter that would go from the prop valve to the stock 1/4" rear brake line. I ended up having Classic Tube CNC bend me a 3/16 mild steel line to follow the same contour as the factory 1/4" line just leave me an additional foot at the prop valve. Worked perfectly.
     

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