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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » New dual bore master cylinder will not fit. Interferes with shock twr

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    3/03/2019 10:46 AM  #1

    TBL66coupe331cid
    Unregistered

    New dual bore master cylinder will not fit. Interferes with shock twr

    Hi - I need help and I am sure that I am not the first and that someone here knows the way around this situation.
    first: 1966 coupe
    331 stroker
    Auto trans (AOD - however car was originally 3-speed manual)
    Power brakes (originally 10" drums)

    I am installing the Mustang Steve front disc conversion for the 12.4" GT rotors/calipers.
    At the point where we need to install the new master, prop valve, new lines and hoses.
    Problem is that the new master cylinder will not fit. It is about 7.25" long & contacts the shock tower.
    Can anyone please point me in the right direction?

    Thanks!
     

     

    3/03/2019 11:51 AM  #2

    6sally6
    Hyper FYIFORD ADDICT

    Offline

    From: Surfside Beach,SC
    Registered: 4/02/2013
    Posts: 6,874

    Re: New dual bore master cylinder will not fit. Interferes with shock twr

    Have NO fear...we got an answer for you!!

    Just not me  I have manual front disc-ez BUTT

    Mustang Steve knows of a short-er power brake hickey that can make the whole combo fit.
    This will keep you bumped-to-the-top.
    Welcome to the best forum on the net.
    6sally6

    Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     

    3/03/2019 8:35 PM  #3

    TBL66coupe331cid
    Unregistered

    Re: New dual bore master cylinder will not fit. Interferes with shock twr

    Thanks for the greeting & the hope there is a solution!

       •Thread Starter
     

    3/04/2019 2:57 PM  #4

    MS
    Forum Originator

    Offline

    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,299

    Re: New dual bore master cylinder will not fit. Interferes with shock twr

    The orignal 65/66 Mustang power brake booster will only work with the original drum brake master cylinder.  MustangSteve has a retrofit power booster that will work for your car. Either follow the power brake link at the top of the forum title page, or go directly to mustangsteve.com. See the 65/66 power brake conversion kit. The PB-5 kit includes everything you need to properly convert the car to power brakes.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    3/09/2019 8:43 AM  #5

    mustang stu
    FYI FORD Member

    Offline

    Registered: 4/15/2016
    Posts: 98

    Re: New dual bore master cylinder will not fit. Interferes with shock twr

    I had to follow up on this post, I figured MS would know. My 67 was converted to power drum brakes
    two years ago,I put in a bendix booster,power drum master cylinder,it was a tight fit,with MS's help
    I was able I was able to get it in (two pieces).With an engine swap coming up (empty engine bay)
    I'm thinking this would be a good time to go to front disc brakes.I have a new extra master cylinder
    from my 69 cougar, it seem's to be longer than the power drum master cylinder. I think I have about a
    1/4" clearance between the end of the master cylinder (drum brakes) and the shock tower. My
    question is did they make two different size power disc master cylinders (overall length)? Or is
    there a different set up I would have to use?        THANKS mustang stu

     

    3/09/2019 6:12 PM  #6

    MS
    Forum Originator

    Offline

    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,299

    Re: New dual bore master cylinder will not fit. Interferes with shock twr

    The 67-70 disc brake master cylinders were the same part. Two different boosters were used.  Midland-Ross through 69, then a mid year 69 change to Bendix occurred.  All these combinations fit the 67-70 Mustangs.  It was a TIGHT fit, but it fit.
    Cars that have been retrofitted to power brakes, even when using all factory parts, do not have the stronger firewall plate the factory used.  Sometimes the installers do not open up the firewall hole to accommodate the booster bellows.  Sometimes they tighten the lower booster studs tighter than the upper studs, bending the thinner firewall and angling the booster downwards.  Since the shock tower gets bigger the lower it exists, any angularity of the booster and master cylinder downward will exacerbate the issue of clearance.
    I believe that some of the reproduction master cylinders are a tad longer than the original disc/drum master, but they will all still fit.


     

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    3/10/2019 9:10 AM  #7

    mustang stu
    FYI FORD Member

    Offline

    Registered: 4/15/2016
    Posts: 98

    Re: New dual bore master cylinder will not fit. Interferes with shock twr

    Dear MS,   Thank's for the input. I will be getting the 67 out of storage (Penna winters) shortly. When
    I converted to power brakes,I tried to put the master cylinder,booster in 1 piece,you told me to do it in
    2 pieces (A BIG HELP!). I did use a template and opened up the firewall and drilled out 2 holes I believe. It should a lot easier with the engine out. I read Sally's post about the brake switch replacement, in my 40's I got upside down (on driver's seat my, head on the floor mat) and changed the switch out. Now in my almost 70's I can still change the switch, but I have to pull the step sill
    plate and driver's seat out.    THANK'S MS!

     

     

     

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