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  1. #1

    Default Help with M1858 master cylinder

    Iíve seen a few posts about people using these master cylinders, and I was able to get my hands on one pretty cheap.
    From what I can tell the stock primary is 9/16-18 and the primary on the 1858 is 7/16- 24. So I would need a reducer with female 9/16 to make 7/16 to fit into the new MC. Iíve found plenty going the other way, but does anybody have a link to where I can find this adapter?


  2. #2


    I hear ya
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    Well...... autozone carried it when I did the conversion on my 86GT a few years ago. I carried the M1858 and the stock line in with me, took about 5 minutes to find the right one.

    The other approach you could take is get/make new lines from the master cyl to the stock proportioning valve.

    Either way works.

    I thought about drilling and tapping as an option too, but that gets difficult with the way brake lines seal a the double flare. Nick the flange and you're out of luck.

    Or after doing some additional reading I found out that the 1" bore master cyl for the 1973 LTD and Torino uses the same sized lines as the four eyed fox and is a direct bolt-up to our booster.

    Both the M1858 and the Torino master cyl are a much less expensive option than the 1993 Cobra master cyl so many seems to go with.

    I REALLY like my M1858 with my 99GT front calipers and 95GT rear calipers in my 86GT. Went Baer rotors when and MM braided lines when I did the 5 lug conversion. 60-0 is less than 100 feet.
    Last edited by erratic50; 02-11-2019 at 12:59 PM.

  3. #3



    Thanks for the reply! Pic is of some 99 PBRís (I need to rebuild and paint) and 95 spindles I picked up on EBay. This MC was just another piece of the puzzle Iím collecting that I got for $13 on Rock Auto.
    I saw fittings where I could use two to get to the size I need, but that may create other figment issues by lengthening the line too much, so itís good to know itís out there. Not sure why it wonít show on the internet search.
    Anyway, I will end up doing the fronts first, and will probably just run 5 lug drums in rear for a bit.
    Should I change this MC with the fronts, or wait for the rear disc conversion?
    Attached Images Attached Images  
    Last edited by Rpw6; 02-11-2019 at 04:43 PM.

  4. #4


    With my car I used a different approach than you are trying so I really don't know what you're going to get for sure. The foxbody 60 mm calipers seemed to work OK with the SN95 rear brakes when I swapped in my 8.8 before converting the front to SN95 so you may get similar results going the other way.

    I would not bother with 5 lug drum. SN95 rearends complete are SO cheap these days. Then all you need to do it "right" is a correct length 5 lug axle with SN95 flanges. I bought Mosier axles for mine.... still haven't gotten around to installing them yet. SN95 brackets can be cut and made to work, or Northern Racing sells a bracket designed for SN95 brakes on fox width rear axles.

    I would replace the balljoints with SN95 balljoints. If the A-arms are in poor condition, Rock Auto sell or Parts geek sells new but I would not run the crappy 79-92 fox balljoints they use in those. Low friction OE 94-95 balljoints are a LOT better for ride and handling.

    You're going to have to pay attention to get your spindles preloaded with enough negative camber when you are installing the spindles. Some oblong the top bolt holes in the strut, others use camber bolts.

    You will need strut spacers or struts specifically designed for the newer style spindles or thing won't work right because the 86 and older spindles are thicker where the strut attaches.

  5. #5


    First off.... I appreciate the help, and detailed replies. Doing the searches and reading every different approach can make you crazy. It’s nice to hear from someone who’s done it and had success.
    I have read about the ball joints, and definitely plan on switching those, instead of using those “spacers”. That just does not seem right or safe.
    I’m prepared for the new struts as well. It seems everything I work on is the odd man out and requires a little extra. That’s fine though, it all pays off in the end!
    Regarding the camber, will caster/ camber plates allow for the necessary adjustments without playing with the strut holes? I was already prepared to have to buy those as well, so if they will get the front end right, I’m fine with that. I’m probably going to look at lowering the car a bit anyway.

  6. #6


    The spacers were used by Ford on the 1993 Cobra R. Lol..... yea, it’s a getto approach in a lot of ways

    It is hard to very hard to get enough negative camber without camber bolts or strut mount elongation

    A good friend of mine used stock balljoints and spacers with 95 spindles on his 86GT. He had to use a camber bolt in the top hole to get it into range even with a caster/camber plate. This gave him enough adjustment to max out positive caster which really helps with any car

    I used Steeda X2 balljoints on my 86GT in attempts to correct bumpsteer with the 95 spindles. In the end I also put on an 18 year old new in box set of HPM caster camber plates too because I was WAY out of range. +6 at max negative!

    Well — Both dropped ride height around 3/4” while shortening the space where struts can “live”. my bumpsteer was still off enough that I bought a Maximum Motorsports bumpsteer kit. moving the spindle upward 3/4” with the balljoint and dropping the ride height another 3/4” via plates aggregated an already tough situation.

    I had to put a jack on a pry bar while using camber bolts top and bottom to get enough adjustment on mine. But when I was done my plates are centered for max caster and I have -2 camber dialed in which is GREAT for cornering around town or with autocross

    If I hadit to do over I may use a normal SN95 balljoint with caster/camber plates and a bumpsteer kit. And probably a lowering spring to get my car where I want it

    the X2’s do drop the roll center which does aid in cornering but there are drawbacks as you can see. Also they are not a low friction balljoint

  7. #7


    With my 85 Saleen clone build Trey is rebuilding for me I stayed 4 lug.

    We went with SN95 balljoints and SN95/SVO adapters and SVO spindles and 87-93 V8 4 lug rotors and strut spacers so the Racecraft struts would work with the spindles. had to tweak a hole in the strut.

    SVO spindles correct Ackerman while accepting the 87-93 4 lug rotors.

    Had to get a bumpsteer kit to address the known bumpsteer problems lowered cars have

    The car is still in build process so we will see how it drives when it’s done

    On the four lug brake upgrade thread some have reported using the SVO spindles with success at Stock ride height. It was one of those deals where I looked at the engineering specs and couldn’t see any reasons why it wouldn’t work.

    Have onion head struts mounts on it right now. Will go to Maximum Motorsports caster camber plates since the NOS HPM plates I ordered never showed up.

  8. #8


    Another piece of the puzzle showed up today vis Fed Ex.... nice new Timken hubs
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  9. #9
    FEP Member
    Join Date
    Dec 2016
    Grand Rapids, MI


    I ran into the same issue when I was researching which master cylinder to use. I searched quite extensively and could not find anybody that made the adapter. In the end I just decided to go with a '94 Cobra master cylinder and the Maximum Motorsports brake lines to adapt to my (soon to be gutted) proportioning valve.
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '97 Thunderbird
    '85 Ford LTD Squire

  10. #10
    FEP Super Member gr79's Avatar
    Join Date
    Jun 2009
    SE Michigan

    Default Use adapter line

    Replace whole line from M/C to p valve directly. Bend as needed.

    Similar situation with my 93 Ranger. Adapting Metric M/C to SAE. Brake lines are AGS Poly-Armourģ from AZ.
    All brake lines have been replaced recently, duplicating factory bends when possible.
    Custom bent metric to SAE M/C adapter lines to the main line unions. The are 8" long, easy to bend tight curves.
    No leaks, stops on a dime like when truck was new. Rotors are stock 261mm/10.2".
    Wish the car had brakes like this. Time to upgrade it from early build 9" rotors to 10".
    Attachment 126318
    Last edited by gr79; 02-15-2019 at 04:57 PM.

  11. #11


    Quote Originally Posted by gr79 View Post
    Wish the car had brakes like this. Time to upgrade it from early build 9" rotors to 10".
    Yea, we hear Mickey Mouse called and he wants his brakes back. Lolz
    -- James

    Favorite thing Iíve said thatís been requoted: ď"40 year old beercan on wheels with too much motor"

    My four eyed foxes:
    "Trigger" - 86 Mustang GT - Black with red interior. 5.0 T5 built as Z. Original motor ~1/2 million miles. 18 yr daily, 10 a toy
    "Silver" - 85 Mustang Saleen 1985-006? (Lol) Rare 1E silver GT / charcoal interior. The car is a little bit of a mystery. Current project bought as a roller, tons of Saleen / Racecraft pedigree

    Also in the stable - my sonís car. 1986 Mustang GT Convertible. Black/Black/Black conversion. 93 leather. VM1 ECU. T5Z

    past foxes -
    1989 Mustang LX Sport 5.0 AOD white/tan black top. Once I ran this one down I caught a wife.
    Wife also had a 1987 Thunderbird Turbo Coupe in the 90's.

    I'm a four eyed pride supporter, are you? Become one today!

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