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  1. #1

    Default Definitive Brake Booster Question 85' GT

    So I finally got the car pretty much gutted for my resto project and before I send it off for paint I was going to attempt the dreaded 93' Cobra Brake booster/MC upgrade (test fit) since the car will be swapped to 5-Lug with SN95 Front Cobra disc brakes and probably the same for the rear. I have done tons of research and have lost sleep over this since there are so many conflicting theories out there about pedal travel and whether or not the upgraded booster really even helps. From what I've gathered a lot of it is based off preference but this setup seems to make the most sense:

    87-93' Fox Non-Cobra Booster (is there actually a difference from the 84-85' boosters?)
    94-95' Cobra MC
    Maximum Motorsports conversion lines
    Gut Stock Prop Valve
    Ford Racing Rear Prop Valve

    Not going with the proper setup at this stage could be bad if I had to go and beat the firewall in after the engine has fresh paint (although I don't really want to beat it in at all). I currently have purchased nothing for this yet and will also not be re-using the stock booster as it looks pretty worn.
    1997 Mustang Cobra - Very First Car
    1985 Mustang GT - RestoMod Work in Progress
    2006 F-150 FX4 - Tow Vehicle

  2. #2
    FEP Senior Member 83gt351w's Avatar
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    I’ve done this very conversion. The 93 Cobra booster fits by gently tapping in the strut tower, not the firewall. I have the following.

    93 Cobra booster
    94/95 Cobra MC
    MM Conversion lines
    Gutted prop valve w/Ford racing adjustable valve
    03/04 cobra brakes front and rear

    There is one thing I don’t like about the set up. It’s the booster. I believe the 87-93 gt booster would give you a little more pedal effort, for the sporty feel. Right now, it doesn’t require much effort at all for the brakes.

  3. #3
    Moderator wraithracing's Avatar
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    Most replacements today show 79-93 boosters (non 93 Cobra) as being the same or interchangeable.

    Depending on which SN95 Cobra brakes you run may affect the actual pedal feel since there are two different size caliper bores. The 94-98 are 38mm bores and the 99-04 are 40mm bores.

    Overall, the setup is essentially the same as I have run on several Foxes. I think you will be happy and just fine with the setup. I personally have the same basic setup on my PC with the 93 Cobra M/C and Booster. It's my least favorite pedal feel. Braking performance is fine, but I will most likely swap out the 93 M/C for the 94/95 Cobra unit when its gets refurbished.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  4. #4
    Moderator wraithracing's Avatar
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    Quote Originally Posted by 83gt351w View Post
    I’ve done this very conversion. The 93 Cobra booster fits by gently tapping in the strut tower, not the firewall.
    That is true for the later year model Four Eyes. I can tell you on my Pace Car I had to beat the H#LL out of the strut tower on my PC to make the 93 Cobra Booster fit. I have done the same install on an 86 and as you stated, it took just a mild beating to work the booster into submission.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  5. #5

    Default

    This is mostly a restoration/street car but it will see some heavy footed driving. I'm guessing my best bet would be to just grab a stock booster with the 94-95' Cobra MC. Is there any specific year booster I should go with or are all fox boosters the same? Also this might sound weird but is their a particular big box auto parts store/manufacturer I should looks for/avoid. I will probably just snatch these parts up at a local big box parts store.
    1997 Mustang Cobra - Very First Car
    1985 Mustang GT - RestoMod Work in Progress
    2006 F-150 FX4 - Tow Vehicle

  6. #6
    FEP Super Member erratic50's Avatar
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    For my money it’s a 1” bore 73 Torino master cyl these days. Direct bolt-on.

    Before this detail I played a lot with M1858 which is also SAE and also 1” bore. One line needs an adapter vs the foxbody.

    stsy with the stock booster

    brakes wise its a lot of preference details.

    I have SN95 99-04 GT brakes on my 86GT with braided lines and performance friction pads (or was it hawk hps?) with Baer 99-04GT drilled/slotted rotors. Rear are hawk or perf friction pads with 95GT brakes. Adjustae proportioning valve also. I run X2 balljoints which drops my frontend center of gravity for handling..... a move plenty people here disagree with and I may not do again

    tires are 245/45/17’s

    All said the brakes are money on the car. It goes 60-0 faster/shorter than my father-in-law’s Z06 which makes me “that” son-in-law I guess.. Oh well, my old piece of crap out accelerates that vette and out corners it too so it’s only fair that I can stop shorter.....

    Cant wait to get my 85 done so we can go for a ride in a quick and fast car — for once. Lol.

    Ive dragged 13 GT500’s down the street with my 86GT cuz spinning ain’t winning...... that car has almost nothing under the hood compared to what’s going into my 85 build. So if I’m being honest, I can’t wait ......

    Remember — educate one grown ass man with hurt feelings at a time. That club is their support group. Send them!

  7. #7

    Default

    Hmmm... interesting hadn't heard about the 73' Torino MC set up. So...

    - Stock Booster (what fox year was best or are they all same?)
    - 73' Torino MC
    - MM Adapter Lines no longer needed
    - Gut Stock Prop valve
    - Ford Racing Rear Prop Valve

    I am also replacing the brake lines that run down the body of the car as well as swapping in a 5-lug swapped 8.8 (31 splines ). I was told by MM that since I was doing this I should use the brake lines/routing out of an 87'+ rather than an 85' as it was a much better route (through Trans tunnel rather than bottom of frame). Is this true?

    Thanks all for the info as I am a firm believer that proper braking in a car is the most important system.
    1997 Mustang Cobra - Very First Car
    1985 Mustang GT - RestoMod Work in Progress
    2006 F-150 FX4 - Tow Vehicle

  8. #8

    Default

    If you are that far, why not consider hydra-boost? Smaller unit, fairly simple to plumb, and more consistent braking over various RPM's.

    That is my path before my 82 hits the road (current Cobra front / rear disks).

    Kenny

  9. #9

    Default

    Sounds fancy... not very familiar with this set up but I'm guessing it uses hydraulic fluid from the power steering to power the brakes rather than engine vacuum? I would also guess I need quite a few extra parts to run this setup?

    Hydraboost Assembly out of a new car
    Adapters
    Brackets
    Newer PS Pump?

    I currently do have everything removed including the pedal box so I can't imagine the swap would be that bad. My only problem is I was considering eliminating the PS all together and moving to a manual rack because I hate PS as the hard lines always seem to develop leaks. My understanding is the newer Flaming River manual racks really aren't that hard to maneuver; however, there might be too much added cost with this conversion since as far as I can tell my current rack is in pretty good shape. I guess I just don't really know enough about the hydra boost brake system have even considered it at this point but I'm always open for suggestions that modernize these older foxes so long as they maintain their factory beauty!
    Last edited by IDriveFords; 03-13-2019 at 11:25 AM.
    1997 Mustang Cobra - Very First Car
    1985 Mustang GT - RestoMod Work in Progress
    2006 F-150 FX4 - Tow Vehicle

  10. #10

    Default

    You would need a unit out of a 1999-2004 GT/ Cobra/Mach 1. Yes, a little more work but anyone who has done it loves the result. There are a few on here who have done it... worth an hour of your time to investigate. Also Maximum Motorsports sells an install kit if you want to save time.

    Kenny

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