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  •  » 99.9% sure I have the wrong m/c

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    6/02/2014 10:10 PM  #1

    rmousir
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    Registered: 4/01/2013
    Posts: 156

    99.9% sure I have the wrong m/c

    Over the last few years I've converted my car to power disc brakes.  I'm 99% sure that some how I have the wrong m/c on the car.  The performance is not right.  Everything related to brakes is new and done right.  The car will not stop strongly.  Its not safe to drive.  In fact it feels like the brake pedal bottoms out (although its not hitting the floor).  I even took my car to a pro mechanic and after some trouble shooting he is convinced I have the wrong master cylinder.  After speaking to him, I agree with him.  So I'm ready to buy another one. 

    This is what I have.

    66 mustang
    5.0 with carb
    c4
    MustangSteve modified pedal hanger and modified pedal.
    fox body 4 cylinder booster
    dual bowl m/c

    For the life of me I can't find the receipt for the m/c but I think it is a 74 maverick ds/dr power brake m/c.  I'm 99.9% sure that it is wrong so my question is what is the part number for the m/c that I wan?

    The site says:
    =14Iron Disc/Drum or Disc.Disc 1.0" bore  $75.00  =14(Similar to 70 Mustang original) =14    
    Aluminum Disc/Disc 1.0" bore   $120     =14 =14(2000 Mustang V6)I've looked at rockauto.com but they have a selection and I want to be sure I get it right this time.I can add a picture if that helps.

    Thanks guys.
    Richardrmousir

     

    6/02/2014 11:33 PM  #2

    True74yamaha
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    From: Salt Lake City
    Registered: 5/07/2013
    Posts: 2,537

    Re: 99.9% sure I have the wrong m/c

    Have you made sure you have gotten the air out of the system? How about what type of brakes are on the car?

     

    6/03/2014 7:00 AM  #3

    rmousir
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    Re: 99.9% sure I have the wrong m/c

    yes.  The current m/c was bench bleed.  Each corner of the car has been bled now 3x.  In the proper order.

    The backs are standard drums with all new hardware, wheel cylinders, shoes.

    The fronts are the scarebird conversion.

    My braking was excellent until I went to power brakes.  My booster is new.  I had my friend, who is a mechanic, review my work because I was doubting what I had done. 

     

       •Thread Starter
     

    6/03/2014 10:54 AM  #4

    True74yamaha
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    From: Salt Lake City
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    Re: 99.9% sure I have the wrong m/c

    You could have routed your lines in a upward arrangement that's trapping air in the system. The other think it could be is the mc like you think your seals could be bad.. Id only go a disc drum master other wise your brake feel won't be right if you use a dis disc master.

     

    6/03/2014 11:29 AM  #5

    MS
    Forum Originator

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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,373

    Re: 99.9% sure I have the wrong m/c

    The Mav MC has 15/16" bore.  It is best used with manual brakes, but I have used them before with the power brake setup with no issues.

    I use 1" bore master cylinders on my kits now.  Part of the service I provide is that when you buy a master cylinder from me, I have already done the homework to be sure you get the correct one.

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

    6/03/2014 11:52 AM  #6

    6sally6
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    From: Surfside Beach,SC
    Registered: 4/02/2013
    Posts: 6,906

    Re: 99.9% sure I have the wrong m/c

    If the brakes were good...."pre-booster"......I'd look at that part first.
    I have ScareBirds on the front(as you know!) butt no power. They are way better than drums butt.....pedal goes wayy down. Check the booster first
    6s6
     

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

    6/03/2014 1:31 PM  #7

    BobE
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    From: White Plains, NY
    Registered: 4/04/2013
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    Re: 99.9% sure I have the wrong m/c

    I'd also start with the booster, I know you indicated the setup has been checked, I'd verify your vacuum line is connected correctly, and no vacuum blockage exists at booster inlet.
    Maybe this setup is not allowing full travel of the MC itself ... maybe it is bottoming out within the booster prior to the full required travel of the MC?

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    6/03/2014 9:18 PM  #8

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
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    Re: 99.9% sure I have the wrong m/c

    BobE wrote:

    I'd also start with the booster, I know you indicated the setup has been checked, I'd verify your vacuum line is connected correctly, and no vacuum blockage exists at booster inlet.
    Maybe this setup is not allowing full travel of the MC itself ... maybe it is bottoming out within the booster prior to the full required travel of the MC?

    Good possibility that with the smaller master cylinder, that is exactly what is happening.

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

    6/04/2014 7:19 AM  #9

    rmousir
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    Re: 99.9% sure I have the wrong m/c

    how do I check to see if the booster is bottoming out before the m/c? I've never seen or heard of that.

    Love how much I learn with this site!

       •Thread Starter
     

    6/04/2014 7:40 AM  #10

    hmartin025
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    Registered: 4/01/2013
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    Re: 99.9% sure I have the wrong m/c

    Unbolt M/C from booster, see if pedal goes to floor. That should tell you?

     

    6/04/2014 9:01 AM  #11

    True74yamaha
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    From: Salt Lake City
    Registered: 5/07/2013
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    Re: 99.9% sure I have the wrong m/c

    I'd ask scarebird to about it... I think that's how those brakes will be. Do you have the kit that uses 68 mustang rotors and c10 or whatever truck calipers? If so you will in my mind have a poor pedal feel. The rotor are .94 nominal thickness those chevy calipers are ment for rotors that have a 1.28" nominal thickness. A huge difference. You are going to be getting a huge stroke cause it's gonna take for ever for the pad to hit the rotor. If I was scarebird I would've just made a bracket to mount newer pbr calipers to those rotors they're a heck of a lot closer in dimentions then those two components are. I don't think you'll get a good pedal feel. I have an 85 chevy truck it this's has a fairly long stroke using similar calipers. So needless to say I'd sell your kit and spend a lil extra and get kh brake conversion kit for your car

     

    6/04/2014 9:11 AM  #12

    BobE
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    From: White Plains, NY
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    Re: 99.9% sure I have the wrong m/c

    I suggest taking the measurements yourself. 
    1. Measure how far from the floor the pedal is when travel stops. 
    2. Remove the booster, and repeat the above measuring how far the actuating rod has traveled with the foot pedal at the previous measured stop point.
    3. Measure the full travel range of the MC by itself.
    4. Measure the full travel range of the booster by itself.
    With the above info, you should be able to determine what, and why, is happening with this setup.

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

     

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