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  •  » Adjustable Proportioning Valve

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    11/10/2020 2:56 PM  #1

    Toploader
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    Adjustable Proportioning Valve

    I have the Mustang Steve Adjustable Proportioning Valve on my car.
    Can anyone tell me what adjustment worked best for them? I'm playing with my set up to see what works best. Thanks.

    1964-1/2 D Code Coupe - 289 V8, 4 Speed Toploader, 3.00 ratio rear, Autolite 4100 Carb, 15" tires, Pertronix ignition
     

    11/10/2020 4:13 PM  #2

    TKOPerformance
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    From: Newark, DE
    Registered: 12/15/2014
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    Re: Adjustable Proportioning Valve

    What's your brake setup?  Disc/drum vs disc/disc the setting will be different because rear discs will do a lot more braking before lockup. 

     

    11/10/2020 7:18 PM  #3

    BillyC
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    Re: Adjustable Proportioning Valve

    I’ve got a disc/disc on my 66. I’ve played with the prop valve a lot and found that I like it best at exactly half way. In other words equal pressure front and rear. 

    "anyone that stops learning is old, whether at twenty or eighty"Henry Ford
     

    11/11/2020 12:59 AM  #4

    Toploader
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    Re: Adjustable Proportioning Valve

    I have a disc front and drum rear set up.
    Stainless Steel Brake Corporation conversion kit and the adjustable proportion valve is from Mustang Steve.
    I was wondering how many turns on either the increase or decrease side.
    Thanks.

    1964-1/2 D Code Coupe - 289 V8, 4 Speed Toploader, 3.00 ratio rear, Autolite 4100 Carb, 15" tires, Pertronix ignition
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    11/11/2020 7:05 AM  #5

    TKOPerformance
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    Re: Adjustable Proportioning Valve

    I would start at 1/4 way out from fully closed with disc/drum.  That should get you close.  Then do some hard stops and see if the back end locks first (reduce pressure) or not at all (increase pressure).  Go no more than 1 turn at a time making adjustments. 

     

    11/11/2020 9:53 AM  #6

    BobE
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    From: White Plains, NY
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    Re: Adjustable Proportioning Valve

    I have a disc/disc setup on my 65 and have the proportioning valve set at mid-way (10 full turns, set at 5 turns), found this works for me.
    From my understanding, the best way to "calibrate" any adjustable item is to set at one end, try it, then move to the other end, try it, and then adjust it based on these two results.  Using this theory, you'll need to test each setting by driving and braking.  I like to use an empty parking lot to test, and at different speeds, like 30, 40, 60 MPH.
    Good luck.

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

    11/11/2020 2:07 PM  #7

    Toploader
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    Re: Adjustable Proportioning Valve

    Thanks guys.
    Just to clarify... Is "Decrease" reducing pressure off the rear brakes and "Increase" increasing pressure to the rear brakes?

    1964-1/2 D Code Coupe - 289 V8, 4 Speed Toploader, 3.00 ratio rear, Autolite 4100 Carb, 15" tires, Pertronix ignition
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    11/11/2020 4:09 PM  #8

    TKOPerformance
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    Re: Adjustable Proportioning Valve

    Toploader wrote:

    Thanks guys.
    Just to clarify... Is "Decrease" reducing pressure off the rear brakes and "Increase" increasing pressure to the rear brakes?

    Yes.

     

    11/11/2020 8:26 PM  #9

    Toploader
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    Re: Adjustable Proportioning Valve

    Thanks...
    So I will wind the valve fully over to increase (rear brakes) and then start working my way back, after starting at a 1/4 of the way (maybe 2 turns) and see how it goes. Does this sound right?
    Based on what Bob E said, I will probably find the optimal adjustment at around 3.5 turns in maybe?

    Last edited by Toploader (11/11/2020 8:27 PM)

    1964-1/2 D Code Coupe - 289 V8, 4 Speed Toploader, 3.00 ratio rear, Autolite 4100 Carb, 15" tires, Pertronix ignition
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    11/12/2020 10:19 AM  #10

    BobE
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    Re: Adjustable Proportioning Valve

    My suggestion is to go from one extreme , full CCW, to the other, full CW.  Try each by braking at the same speeds.  The rears may lock up way too early at one end, and the fronts at the other.  Depending on how many turns there are, one extreme to the other, will give you an idea of where to try next.
    Remember, my settings are based on a disc/disc setup.

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

    11/12/2020 4:09 PM  #11

    TKOPerformance
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    From: Newark, DE
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    Re: Adjustable Proportioning Valve

    Toploader wrote:

    Thanks...
    So I will wind the valve fully over to increase (rear brakes) and then start working my way back, after starting at a 1/4 of the way (maybe 2 turns) and see how it goes. Does this sound right?
    Based on what Bob E said, I will probably find the optimal adjustment at around 3.5 turns in maybe?

    I would do the opposite.  Essentially shut off the rear brakes, then go two turns increased from there.  Test and see if the rears lock up prematurely or not at all.  If its not at all go another turn increased and retest.  Keep doing that until the rears lock up prematurely, then go 1/2 turn decreased and it should be pretty spot on.  I'll bet that 1/4 will get you close though, most disc/drum systems I've tuned have used the rears for at most 30% of braking.  Disc/disc setups can get close to or even at times exceed 50/50 (rear tire contact patch plays a role in this). 
     

     

    11/12/2020 5:08 PM  #12

    Toploader
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    Re: Adjustable Proportioning Valve

    Ok, thanks very much. I will give it a try.

    1964-1/2 D Code Coupe - 289 V8, 4 Speed Toploader, 3.00 ratio rear, Autolite 4100 Carb, 15" tires, Pertronix ignition
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    11/12/2020 7:09 PM  #13

    Toploader
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    Re: Adjustable Proportioning Valve

    With a disc / drum set up, what is the optimum proportion for braking?
    I am currently at three turns in (heading towards the increase direction) from the rear brakes being shut off and will see how that goes for a bit.
    Thanks.

    1964-1/2 D Code Coupe - 289 V8, 4 Speed Toploader, 3.00 ratio rear, Autolite 4100 Carb, 15" tires, Pertronix ignition
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    11/13/2020 6:15 AM  #14

    TKOPerformance
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    From: Newark, DE
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    Re: Adjustable Proportioning Valve

    Optimum braking is typically where all 4 wheels lock up at the same time under hard braking.  BUT, it depends a bit on the driver too, some prefer the rears to lock up just a tiny bit before the fronts because the idea is that you can still steer a car with locked rear brakes, but you can't steer a car with locked front brakes.  This is more for guys that have done a lot of racing, etc.  If you are used to normal cars then the OEMs set it so all 4 lock up at the same time, with maybe just a smidge of bias toward the rear locking first. 

     

    11/13/2020 8:08 PM  #15

    Toploader
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    Re: Adjustable Proportioning Valve

    I have adjusted the proportioning valve as described here. Last test run I did about 55 and jammed the brakes on. The rear did lock up just a bit and the rear of the car started to peel out. So based on that, I'm pretty close and probably need to decrease maybe 1/2 a turn.

    1964-1/2 D Code Coupe - 289 V8, 4 Speed Toploader, 3.00 ratio rear, Autolite 4100 Carb, 15" tires, Pertronix ignition
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    11/14/2020 6:34 AM  #16

    TKOPerformance
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    From: Newark, DE
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    Re: Adjustable Proportioning Valve

    Yep, go 1/2 turn decreased and retest.  You can really fine line it with 1/4 turns, etc. if you think its merited.  I just learned years ago that to get close there was no point in going 1/2 turn until you were at least close, otherwise it takes forever and it seems your adjustments aren't doing anything. 

     

     

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