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  1. #1

    Default 85 proportioning valve

    I have everything to redo my brake system including a new ford adjustable proportioning valve, but I'm not sure on how to "gut" the old one so it isn't operational anymore........I'm keeping it so I don't have to re-plumb that area below the M/C.........I'll be installing the new proportioning valve over by the passenger side hood hinge....... any help will be much appreciated...Thanks

  2. #2

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    From the instructions from my motorsport brake kit:
    Remove the plug, spring, seat and plunger from the front of the valve. Remove the O- ring from the plug and install it on the special plug without the hole. Install new plug without the hole in the proportioning valve.
    Plug without hole:
    https://lmr.com/item/M2450A/Mustang-...ing-Valve-Plug

    Mike
    85 GT - owned since 87

  3. #3

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    thanks for the information!........and just to make certain this will work to disable the factory proportioning valve even though I'm keeping the stock rear drum brakes?

  4. #4
    FEP Power Member qtrracer's Avatar
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    Default

    Quote Originally Posted by pw84 View Post
    thanks for the information!........and just to make certain this will work to disable the factory proportioning valve even though I'm keeping the stock rear drum brakes?
    You have to understand what the prop valve is meant to do. It is designed to reduce the rear brake pressure slope at a "knee point" to avoid rear lock before front lock. The stock prop valve is engineered with the knee point fixed to optimally reduce pressure with the rear drum/front disc brake set-up on your 85. A manual prop valve allows the user to move the knee-point up and down the pressure slope to account for non-stock brake components. It is not designed to overcome imbalanced F/R brake torque bias.

    Gutting the stock prop valve is only necessary when swapping to non-stock rear discs because the stock prop valve was not engineered with this combo in mind. You would be much better served leaving the stock prop valve operational until you swap to a rear disc set-up. If you gut the stocker and insert the manual prop valve, you will have to spend a lot of time testing your manual prop valve settings to get the correct knee-point setting. Rear brake lock first is a recipe for a spin-out.

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