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  1. #1
    Administrator SVOeric's Avatar
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    SVO's: 86-1C & 86-1E

    85.5 needing some brake upgrades

    Previous owner had done some work, and don't think the parts are playing together all that well.

    I have to dig in, but not sure which brake-booster it has, or which master cylinder it has.
    all I know, right now, when I press the pedal, it's hard as a rock, and before the brakes lock, I bottom out. (not on the floor-board, but feels like I've hit the end of the master-cylinder.

    For now, I want to keep stock brake calipers (and my 16" wheels), and prop valve (since this one appears to work, however there is a chance it's part of the problem, but i don't think so).

    Is the best combo the stock parts? I seem to remember some details around a 93 cobra booster & master cylinder ?? Heck these days, maybe even the newer 2005 up stuff ? just wondering what's been tried, and what everyone likes. I personally think the SVO pedal is a bit heavy in stock config.

    Thanks
    Eric C
    SVOCA Webmaster

  2. #2
    Administrator SVOeric's Avatar
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    SVO's: 86-1C & 86-1E
    Thinking this is going to be my next stop...

    Click image for larger version. 

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    I considered going the 93 cobra brake booster, but i'm not a fan of beating the crap out of my shock-tower to get it to fit.

    04 GT (what this is from), should have 1-1/16 bore size, should be able to push enough volume, and still have a lighter touch on the pedal.

    I'll just need to work out the adapters/plumbing for the brake lines, as well as the power-steering lines.
    Thinking the stock 04 Power-Steering lines may work, as everything in those cars is so close to where the SVO is anyway. handy that I do have an 03 here to measure from

    Pretty sure the SVO power-steering pump should handle it without issue.
    I'll pop some pics when I do this upgrade to show what I'm doing.
    Eric C
    SVOCA Webmaster

  3. #3
    OVER-BOOST!! svono50's Avatar
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    SVO's: 86 1C
    Eric, cool project. Unfortunately the mjbobbitt page no longer seems to exist, which had all the interchange info on it from what I remember. I knew I should have downloaded the text off that page and archived it.

    Do our stock masters use a 1-1/16 or 1-1/8 bore?? Sounds like you have a smaller bore master cylinder than the stock unit in any case. Does it have the 'large' reservoir or is it a 'small' reservoir unit? That could give you a clue as to whether or not it has a smaller bore.

    I like the idea of a hydro-boost unit, looking forward to your project info.
    Last edited by svono50; 05-26-2017 at 10:11 PM.
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  4. #4
    OVER-BOOST!! svono50's Avatar
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    SVO's: 86 1C
    Hey, just found a video showing how you can get that 93 booster into our cars without any modification to the strut tower (see link below). It does require the slotting of (2) of the booster mounting holes to allow it to rock into position and it tucks in behind the tower. I think the hydro-boost solution is a bit more elegant, but just wanted to toss out the info.

    https://youtu.be/_FY6PovUod8
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  5. #5
    Administrator SVOeric's Avatar
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    SVO's: 86-1C & 86-1E
    the SVO has a 1 -1/8 master cylinder in stock form.
    Already ordered the hydraboost, just working on sourcing the hoses now.
    Eric C
    SVOCA Webmaster

  6. #6
    OVER-BOOST!! Bruce's Avatar
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    SVO's: 86 1E
    I bought a stock MC from Rock Auto a year or so back. Aluminum and everything. Wasn't there an issue with the line threads being metric vs American?
    Bruce

  7. #7
    Administrator SVOeric's Avatar
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    SVO's: 86-1C & 86-1E
    There will be some line issues im sure. The plan is to use the 04 cobra, booster, master cylinder, and prop valve. The 04 cobra brake setup is very close to the SVO's. I think it will work well.
    Only place that will be an issue is the hard lines to the prop valve, and i think i can find adapters pretty easily

    Im more concerned wth what i will find with the lines from the power steering
    I really hate that feeling coming off boost grabbing brakes and the pedal being hard as a rock. Maybe its just because the cam i have, but hydroboost should stop that!
    Eric C
    SVOCA Webmaster

  8. #8
    OVER-BOOST!! gbeaird's Avatar
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    SVO's: '86 2R
    Do you have a check valve inline in the vacuum hose for the brake booster? It may not stop all of it, but can certainly help some.
    Gene Beaird,
    86 2R SVO, G Stock,
    Pearland, Texas

  9. #9
    Administrator SVOeric's Avatar
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    SVO's: 86-1C & 86-1E
    There are actually a couple check-valves in the system, and I've verified they are all there and working.
    Eric C
    SVOCA Webmaster

  10. #10
    OVER-BOOST!! svono50's Avatar
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    SVO's: 86 1C
    Interesting, I haven't experienced that 'hard as a rock off-boost' feeling you describe, even with all my on-track run time?!? Seems a bit strange, wonder if your boosters are not working properly rather than the check valve(s)??
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  11. #11
    Administrator SVOeric's Avatar
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    SVO's: 86-1C & 86-1E
    it's very likely the cam I'm running Ted, as it was never this bad with the ranger cam, but I could still tell a difference when trail-braking on an auto-x.
    Eric C
    SVOCA Webmaster

  12. #12
    OVER-BOOST!! GAboySVO's Avatar
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    SVO's: 2 - 9Ls
    Eric, If the brake calipers are stock front and back and the pedal is as you say it is, then it sounds like the master cylinder bore is under sized or your brake booster is not working. You may want to read my write up I did with my Cobra brake upgrade. There is some math that goes into matching the MC bore with the caliper bore.
    Mike S

    '86 SVO 9L Leather
    '86 SVO 9L Road Warrior
    '96 300ZXTT

  13. #13
    OVER-BOOST!! Bruce's Avatar
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    SVO's: 86 1E
    What cam are you running?
    Bruce

  14. #14
    Administrator SVOeric's Avatar
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    SVO's: 86-1C & 86-1E
    yep, I Agree Mike. Do have stock SVO front and rear calipers.
    But smaller bore, means --more leverage-- (in hydraulic terms) and softer pedal, for more brakes (assuming you get enough fluid to the calipers)
    Larger bore means more fluid, but less 'feel'

    The math does work out, 1-1/16 vs 1-1/8 bore . should still be enough fluid, and have a bit more feel, and if it my math is wrong, The SVO Master cylinder can be adapted to the hydraboost booster.

    The hydroboost is not for 'normal' breaking... trail braking when auto-x'ing or that occasion where you hit the boost, and see a cop, and grab the brakes...
    both my SVO's have a hard pedal in that situation. Think the SVO is, and always has been a good candidate for a hydroboost booster.
    Eric C
    SVOCA Webmaster

  15. #15
    OVER-BOOST!! GAboySVO's Avatar
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    SVO's: 2 - 9Ls
    Quote Originally Posted by SVOeric View Post
    yep, I Agree Mike. Do have stock SVO front and rear calipers.
    I have stock rears and Cobra 13" fronts with a manual proportioning valve with 1 turn of bias to the rear.
    Mike S

    '86 SVO 9L Leather
    '86 SVO 9L Road Warrior
    '96 300ZXTT

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