Proportioning valve confusion

Discussion in 'The whoa and the sway.' started by Ant Legrand, Feb 26, 2019.

  1. Ant Legrand

    Ant Legrand Well-Known Member

    I'm in the middle of a drum-to-disc (front) conversion on my 1967 Special. The car was originally equipped with power drum brakes.

    The kit I got came with this style of proportioning valve. https://www.inlinetube.com/products/pr102 Now, the confusion is, can I keep the original distribution block mounted on the frame rail connected and add the new PV between that and the master cyl? Or do I have to eliminate that original block on the frame and run new lines up to the new PV? My idea was to keep it so I wouldn't have to run new lines and also to keep the brake warning switch connected. Or does the warning light need to be connected to the new PV? The instructions for these new parts seem to be impossible to find.

    PR102.jpg
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Anthony,
    What you have pictured is a combination valve. It's called a combination valve because it combines a Hold off (metering) valve, warning sender, and a proportioning valve.

    CombinationValve.JPG

    In 1967, I believe the hold off valve was separate and mounted near the Master Cylinder. Your car was originally drum brakes, so it would not have a hold off valve at all. Not sure there was a proportioning valve at all in 1967. If it is a simple distribution block with no other function, you might be able to just add the combination valve. You are changing the Master Cylinder, correct?
     
    Last edited: Feb 26, 2019
  3. dl7265

    dl7265 No car then Mopar

    The block on the frame is the same for disk/drum.. if the kit you got was for a 70 style car then you would have the hold off valve at the MC.
     
  4. BrianTrick

    BrianTrick Brian Trick

    That brass valve pictured above is meant to run by itself. No other valve needs to be run with it. That is a modern replacement of the 71-72 style disc brake valve.
     
    GranSportSedan likes this.
  5. Ant Legrand

    Ant Legrand Well-Known Member

    Thank you all for clarifying this. It seems that it would not be of any use to have the factory distribution block with the pressure differential switch located downstream of the proportioning function of the new combination block. I will run new lines from the new combination block down to the factory lines and eliminate the original distribution block.

    And yes I am installing a new master cyl provided in the kit.
     
  6. BrianTrick

    BrianTrick Brian Trick

    I just install the new valve where your existing block is located. It does not need to be mounted next to the master cylinder. That was a 70’s Camaro thing,but it is nice for custom builds,or to get it away from headers.
     
  7. Ant Legrand

    Ant Legrand Well-Known Member

    I guess the lines need to be bent a little to do that? That sounds like a better option.
     
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Or cut and re flared. You'll see when you actually fit it.
     
  9. DasRottweiler

    DasRottweiler -BuickAddict-

    Doing the same thing to my 70'Lark. Was all power drum , will be putting disc brakes in the front. I'm planning on removing the distribution block and extending the rear line so I can mount the pr102 proportioning valve away from my MT/SS headers. Block is to close for comfort, IMO....Althou I have had no issues as of yet with the drums still installed. Jim
     
  10. BrianTrick

    BrianTrick Brian Trick

    Your existing lines won’t be long enough to come up from the bottom and mount the valve next to the master. You do have enough line if you want to roll it up just on top of the frame rail,but that is about as far as your leash will go.
     
  11. DasRottweiler

    DasRottweiler -BuickAddict-

    I'll extend it , need to pop the hood and review my options. Not gonna happen til mid summer. Jim
     
  12. Ant Legrand

    Ant Legrand Well-Known Member

    I was looking at it again and it seems there’s no easy way to do this. Seems like some of the fitting sizes are different on original compared to new combination valve. Cutting and flaring lines down by the frame won’t be easy I wouldn’t think.
     
  13. BrianTrick

    BrianTrick Brian Trick

    You might only need to change the short line from the block to the driver’s front brake hose. That size can be different from drum to disc. Do NOT use any unions to extend your lines.
     
  14. Ant Legrand

    Ant Legrand Well-Known Member

    It seems like the rear outlet on Master cyl is also a different size than the rear inlet on the new combination valve. How do I accommodate that?
     
  15. Ant Legrand

    Ant Legrand Well-Known Member

    Also, point taken about unions but why are they not good? How is it different than going through distribution blocks?
     
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Use different fittings on each side. That will mean flaring your own lines.
     
  17. Ant Legrand

    Ant Legrand Well-Known Member

    This is getting complicated. It's just funny to me how the instructions for these kits are super detailed when it comes to removing and installing the actual brakes, which is pretty easy, but they gloss right over the trickiest part which is how to connect the lines! Thanks for all the help, this forum has been super helpful to me many times.
     
  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Welcome to the world of working on old cars, where Murphy's Law reigns supreme, and nothing ever, ever, goes as planned.:D
     
    Ant Legrand likes this.
  19. BrianTrick

    BrianTrick Brian Trick

    All they are concerned about is selling the part.
    Yes,the rear outlet on the master is larger,but look at the fitting at the other end of that same line,where it goes to the block. It should be smaller.
     
  20. Ant Legrand

    Ant Legrand Well-Known Member

    I found that 3 of the fittings on the new combo valve are different compared to the original one.

    PR102.jpg

    Also, since it is significantly larger overall than the old one, I would have to cut the line back that goes to the rear brakes, and flare it with a 9/16"-18 tube nut. The orig fitting here is a 1/2"-20. But I found that there are several bends towards the end of this line, and I just don't feel very confident trying to flare it under the car in that tight space where it is.

    My new plan is to mount the new combo valve up near the master where the kit intends it. Then I will run a new (front) 3/16 line with 3/8" fittings to a Tee down on the frame where the orig block was. I will have to make a new drivers-side front line. Then I am making up a new (rear) 1/4" line with 1/2"-20 tube nut to connect with an inverted flare union to the rear brake line, and a 9/16"-18 tube nut up top to connect to the new combo valve. I tried to avoid any unions but I don't see how else I can do this without running a new line all the way to the rear axle.
     

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