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65 disc brake master cyl fittings

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    #16
    Had a better look at the prop valve today and noticed the pipe coming from the rear is going to the front pass side brakes, instead of the rear, somebody marked front at the back of the valve and rear at the front. I'm thinking nearly everything is wrong. I've enclosed a pic showing the layout.
    Dodge Dart GTS 440 RPM heads .590 cam NA 3150#
    1.44 60ft 6.43 at 106.78, 10.14 at 132.88 mph
    Best ever 60ft 1.36

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      #17
      I had a look at your sketch. First off this type of prop valve doubles as the distribution block. The large rear bowl of the master cylinder should work the front brakes. The prop valve has two inlets for the pipes from the master cylinder and three outlets. Two of the outlets will be for the front passenger and drivers side brakes. Associated with these outlets will be the inlet which connects to the large bowl rear side of the master cylinder. These ports do not have any valves in them and should be straight through ports just like a distribution block. If you can identify these then the remaining outlet is for the rear brakes and the other inlet for the front master cylinder bowl outlet. The prop valve should be in the line to the rear brakes. It sounds as if your car has been plumbed incorrectly.
      Allan

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        #18
        I've sent you a clearer pic and a possible solution, using a GM PV2.
        Attached Files
        Dodge Dart GTS 440 RPM heads .590 cam NA 3150#
        1.44 60ft 6.43 at 106.78, 10.14 at 132.88 mph
        Best ever 60ft 1.36

        Comment


          #19
          Originally posted by deaks View Post
          I've sent you a clearer pic and a possible solution, using a GM PV2.
          Hi,
          On the first pic I think the only thing needed is that the inlets from the master cylinder need to be swapped. The second picture looks good. The switch in the middle is for a light on the dash to indicate that one brake circuit is leaking and faulty. There is a shuttle valve in the prop valve block that moves when one circuit fails to make the light come on. This type of valve was used on many cars and some never had a light. I have never wired it up on my car because if one circuit fails you will notice it on the brake pedal travel.
          Allan

          Comment


            #20
            Yeah, the switch activates when the piston moves across, to maintain brakes. If I swap the inlets, I still have the rear output going to the front brakes.
            Dodge Dart GTS 440 RPM heads .590 cam NA 3150#
            1.44 60ft 6.43 at 106.78, 10.14 at 132.88 mph
            Best ever 60ft 1.36

            Comment


              #21
              Originally posted by deaks View Post
              Yeah, the switch activates when the piston moves across, to maintain brakes. If I swap the inlets, I still have the rear output going to the front brakes.
              Yes I saw that in your earlier post. Obviously, that needs correcting. If one front brake was on full pressure and the other fed through the prop valve I am surprised you didn't notice the car pulling to one side.
              Allan

              Comment


                #22
                Originally posted by deaks View Post
                Yeah, the switch activates when the piston moves across, to maintain brakes. If I swap the inlets, I still have the rear output going to the front brakes.
                As far as I remember the only thing the shuttle does is activate the light, it does not close off anything to maintain pressure on one side or the other. You don't need that distribution block at all, as Alan says you will know from the pedal if you have a leak, the dual circuit part is all taken care of in the master cylinder. An adjustable proportioning valve in the line to the rear is all you really need.

                Comment


                  #23
                  Well, I've read that it blocks that part of the circuit off, so you don't lose all your brakes and the light flags the problem up. Surely, a distribution block wouldn't have a piston in there. The combination valve is around 100 new.
                  Dodge Dart GTS 440 RPM heads .590 cam NA 3150#
                  1.44 60ft 6.43 at 106.78, 10.14 at 132.88 mph
                  Best ever 60ft 1.36

                  Comment


                    #24
                    Originally posted by deaks View Post
                    Well, I've read that it blocks that part of the circuit off, so you don't lose all your brakes and the light flags the problem up. Surely, a distribution block wouldn't have a piston in there. The combination valve is around 100 new.
                    I read up on proportioning valves and other valves when I did my disc brake conversion. Simple proportioning valves fit in the rear brake line and don't have any lights etc so you still need a distribution block. Adjustable proportioning valves have an adjustable valve but they don't actually vary the pressure to the rear brakes but the pressure at which the proportioning begins. The percentage of pressure applied to the rear brakes is a function of the dimensions of a double piston in the proportioning valve itself. Initially under light braking pressure in the front and rear brake systems will be the same until the hydraulic pressure overcomes the spring holding the proportioning piston against its seat. After this the pressure in the rear brake system is controlled as a proportion of the front brake pressure. Thie point at which proportioning begins is called the split point. In adjustable valves the pressure of the spring on the proportioning piston is varied by turning the valve so it's actually the split point that is moved, or the point at which the valve begins to proportion the pressure.

                    The brass proportioning valves that double as a distribution block and contain the warning light also have a metering valve in them on the front brakes. The purpose of this valve is to hold off hydraulic pressure going to the front brakes until the back brakes are beginning to be applied. The theory being that disc brakes have no return springs whereas drum brakes have quite powerful return springs on the shoes, thus under light braking the drums will always be catching up with the discs, so the metering valve allows hydraulic pressure to go to the back brakes to start applying them before the metering valve opens to the discs. The metering valve opens at very low pressure before real braking begins.

                    The piston in the warning light has O ring seals on it to separate the front and back circuits and moves just enough to make the light come on. It doesn't generally block off the damaged circuit but on some designs it does.

                    I went for the valve with the metering function because I figured that car manufacturers wouldn't spend a cent more than they had to so if a metering valve wasn't necessary, they wouldn't have put it in.
                    Allan

                    Comment


                      #25
                      Originally posted by deaks View Post
                      Well, I've read that it blocks that part of the circuit off, so you don't lose all your brakes and the light flags the problem up. Surely, a distribution block wouldn't have a piston in there. The combination valve is around 100 new.
                      It's possible, but in the case of late 60's Fords and Mopars that distribution block with the shuttle switch does not shut off any fluid flow through it (it would be quite dangerous if it did).

                      I believe both of your pictures show distribution blocks but not proportioning valves. If you can be sure that the 100 combination valve is good for your set up then it seems a reasonable deal.

                      If you want to experiment to dial out any potential rear lock up then a pipe from the larger m/c bowl to a t piece to the fronts and a single line from the smaller bowl with an adjustable valve to the rear will work fine. If you need a dash warning light those valves that you illustrate are the way to go.

                      Comment


                        #26
                        Originally posted by richard View Post

                        It's possible, but in the case of late 60's Fords and Mopars that distribution block with the shuttle switch does not shut off any fluid flow through it (it would be quite dangerous if it did).

                        I believe both of your pictures show distribution blocks but not proportioning valves. If you can be sure that the 100 combination valve is good for your set up then it seems a reasonable deal.

                        If you want to experiment to dial out any potential rear lock up then a pipe from the larger m/c bowl to a t piece to the fronts and a single line from the smaller bowl with an adjustable valve to the rear will work fine. If you need a dash warning light those valves that you illustrate are the way to go.
                        How is your car plumbed.
                        Dodge Dart GTS 440 RPM heads .590 cam NA 3150#
                        1.44 60ft 6.43 at 106.78, 10.14 at 132.88 mph
                        Best ever 60ft 1.36

                        Comment


                          #27
                          Originally posted by ALLAN R View Post

                          I read up on proportioning valves and other valves when I did my disc brake conversion. Simple proportioning valves fit in the rear brake line and don't have any lights etc so you still need a distribution block. Adjustable proportioning valves have an adjustable valve but they don't actually vary the pressure to the rear brakes but the pressure at which the proportioning begins. The percentage of pressure applied to the rear brakes is a function of the dimensions of a double piston in the proportioning valve itself. Initially under light braking pressure in the front and rear brake systems will be the same until the hydraulic pressure overcomes the spring holding the proportioning piston against its seat. After this the pressure in the rear brake system is controlled as a proportion of the front brake pressure. Thie point at which proportioning begins is called the split point. In adjustable valves the pressure of the spring on the proportioning piston is varied by turning the valve so it's actually the split point that is moved, or the point at which the valve begins to proportion the pressure.

                          The brass proportioning valves that double as a distribution block and contain the warning light also have a metering valve in them on the front brakes. The purpose of this valve is to hold off hydraulic pressure going to the front brakes until the back brakes are beginning to be applied. The theory being that disc brakes have no return springs whereas drum brakes have quite powerful return springs on the shoes, thus under light braking the drums will always be catching up with the discs, so the metering valve allows hydraulic pressure to go to the back brakes to start applying them before the metering valve opens to the discs. The metering valve opens at very low pressure before real braking begins.

                          The piston in the warning light has O ring seals on it to separate the front and back circuits and moves just enough to make the light come on. It doesn't generally block off the damaged circuit but on some designs it does.

                          I went for the valve with the metering function because I figured that car manufacturers wouldn't spend a cent more than they had to so if a metering valve wasn't necessary, they wouldn't have put it in.
                          What valve do you use Alan.
                          Dodge Dart GTS 440 RPM heads .590 cam NA 3150#
                          1.44 60ft 6.43 at 106.78, 10.14 at 132.88 mph
                          Best ever 60ft 1.36

                          Comment


                            #28
                            Originally posted by deaks View Post

                            What valve do you use Alan.
                            It's this one

                            https://www.ebay.com.au/itm/231631393689
                            Allan

                            Comment


                              #29
                              That looks like the one, I already have, how is yours plumbed.
                              Dodge Dart GTS 440 RPM heads .590 cam NA 3150#
                              1.44 60ft 6.43 at 106.78, 10.14 at 132.88 mph
                              Best ever 60ft 1.36

                              Comment


                                #30
                                After looking at some ford setups, the ones with the same prop valve as mine, are plumbed the same on the outputs, so I've swapped the two inputs and the brakes are a lot better but the travel is quite a lot, so I'm going to readjust the pushrod.
                                Dodge Dart GTS 440 RPM heads .590 cam NA 3150#
                                1.44 60ft 6.43 at 106.78, 10.14 at 132.88 mph
                                Best ever 60ft 1.36

                                Comment

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