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  • Brake Upgrades

    Anyone out there combined a stock non-disc brake Hydrovac (the one I have was for a truck according to the fellow I got it from) with a dual chamber master cylinder in a Hawk with Jim Turners front disc conversion? I have assembled all the parts except the vacuum line and flex lines to integrate the hydrovac. The m/c is the Jeep/AMC unit Mr. Turner lists as his first choice for the under floorboard install. I am using a metering valve to the fronts and a proportioning valve and the appropriate residual check valves.

    Lew in Escondido, CA

  • #2
    No can do, you'd need two hydrovac's with a dual MC.

    Studebaker On The Net http://stude.com
    64 R2 4 speed Challenger (Plain Wrapper)
    63 R2 4 speed GT Hawk
    55 Speedster
    50 2R 10 truck
    JDP Maryland

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    • #3
      I think there should be information posted somewhere that a (single) hydrovac/dual MC will not work. This question seems to come up a lot lately. In theory the dual MC is safer, but in practice I think the issue is way overblown and everyone seems to be jumping on this type of conversion before thinking about it. This is especially true if switching to disk front brakes and going to a manual dual MC setup, you will definitely need more pedal pressure than you needed before to make it work.

      If you are determined to go the dual M/C route w/ power brakes you will either need 1) 2 hydrovac units one for the front and one for the back with some type of proportioning valve setup; or 2) adapt a hydroboost unit, driven off of the power steering pump; or 3) remote vacuum power unit with electric pump (street rod stuff). #2 or #3 will run you $500 before plumbing.

      Dan White
      64 R1 GT
      64 R2 GT
      Dan White
      64 R1 GT
      64 R2 GT
      58 C Cab
      57 Broadmoor (Marvin)

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      • #4
        I agree with Dan. I got trapped into the Turner conversion and the dual M/C upgrade and it does not work. From what I can tell, the single M/C with the power booster will not work either as the Studebaker drum/drum power booster is different from the Stude disc/drum booster. The drum/drum booster must have a built in residual check valve designed for pressure on a drum set-up which is too much for the disc system and holds the calipers on. Also, I found out the hard way, that the power brake pedal is different from the standard brake pedal and does not provide enough pressure to make standard brakes without the booster work. I think that Mr. Turner should have been aware of the complications and been able to advise customers accordingly.
        I feel I am unable to keep my Hawk close to stock and may need to completely redesign with a GM power boost, proportioning valve and M/C mounted on the fire wall. What do you mean by a metering vzlve?

        '62 Hawk
        '30 Chev Coach
        sigpicJohn Esmonde
        Holland Landing, Ontario
        Canada
        \'62 Hawk
        \'60 Lark Regal Convertible
        \'30 Chev Coach

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        • #5
          Johnesmonde you might want to advertise for a disk/drum hydrovac here and see what you find. I was not aware of the pedal difference, but you might want to see if someone has either a pedal and/or check the part #s to see if there really is difference, or if it is the plunger rod that is a different length. My Hawk had been converted to manual drums all around by the previous owner (it did function OK that way with a disk MC) and I wanted to change back and did find the correct hydrovac at a swap meet. The other possibility is to have yours rebuilt with the repair kit for a disk/drum hydrovac. I know when I had mine rebuilt the guy called and said hey I don't have the parts for this model, the seals were different (I would definitely look in the service manual to see if this will work before you try it however, you should be able to find diagrams for both)!! I had to find a kit from one of the Stude part guys. I also bought a rebuilt disk/drum MC from SASCO for about $70 I believe but that was some time ago. I would try to stay stock looking as much as possible. If you start hacking the firewall and put in hanging pedals and you still have problems that will be a tough one to patch up.

          If the hydroboost will not fit under the floor the remote Powerboost from ECI can be put in the trunk and keep thing neat and tidy: http://www.ecihotrodbrakes.com/remote_booster.html



          Dan White
          64 R1 GT
          64 R2 GT
          Dan White
          64 R1 GT
          64 R2 GT
          58 C Cab
          57 Broadmoor (Marvin)

          Comment


          • #6
            Thanks Dan! I'll look into it.

            John.

            '62 Hawk
            '30 Chev Coach
            sigpicJohn Esmonde
            Holland Landing, Ontario
            Canada
            \'62 Hawk
            \'60 Lark Regal Convertible
            \'30 Chev Coach

            Comment


            • #7
              Thanks to all for your input. Kinda wish I had paid more attention in my fluid dynamics class in college. Correct me if I am wrong, but in the Stude disc/drum set up with the single chamber master cylinder, the hydrovac gets a hydraulic 'signal' from the M/C and does nothing more than 'amplify' that 'signal' using engine vacuum to push fluid to the calipers in front and the wheel cylinders in back. I don't have my service manual with me so I can't look at it at this moment, but perhaps there is a difference in the master cylinder that is used in the stock Stude disc/drum set up? That difference being no built in check valve? Would the check valve be upstream in the Hydrovac itself? Master Power brakes makes a Hydrovac style booster (Midland) that is advertised to work in a disc/drum configuration but only boosting the front. There has to be a way to make this work with a stock Hydrovac. The metering valve I mentioned is a device that delays fluid from being applied to the rear wheels, preventing them from locking up in a panic stop.

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              • #8
                Correction, the metering valve ensures pressure reaches the rears first.

                Comment


                • #9
                  jcstude I believe you are correct that there is no check valve in the Stude MC for disk/drum setup. I seem to remember that is what the guy at SASCO told me when I order my replacement, otherwise they are the same as the drum/drum unit. What you might want to do is use the drum/drum hydrovac and run the high pressure out line into a "T" for front and back. Out of the "T" run the line to the back straight out and the line to the front through a proportioning valve (going to another "T" for right and left) the adjust to the proper pressure. That should probably work. This may be a way for Johnesmonde to do his setup also?

                  Dan White
                  64 R1 GT
                  64 R2 GT
                  Dan White
                  64 R1 GT
                  64 R2 GT
                  58 C Cab
                  57 Broadmoor (Marvin)

                  Comment


                  • #10
                    If you use a prop valve it should cut the pressure to the *rears* on a disc/drum setup, not the fronts. The rears will have much more brake torque for any given line pressure than the fronts as they are self energizing drums (assuming the car was converted from a drum/drum car.)

                    As to the pedal being different power vs. non power on my '55 coupe there are two holes in the brake pedal where you can hook up the MC pushrod, have you tried using the hole closest to the pivot for more leverage? Will cost you a bit in pedal travel but you might find that you like the feel and don't need the booster after all.

                    I've had C-K's both with and without power brakes, granted both of them 4-wheel drum cars, but I have to say I much prefer driving the one with manual brakes. It requires a bit more effort, but doesn't throw you into the windshield if you sneeze while braking either.

                    good luck,

                    nate

                    --
                    55 Commander Starlight
                    62 Daytona hardtop
                    --
                    55 Commander Starlight
                    http://members.cox.net/njnagel

                    Comment


                    • #11
                      God bless the authors of the Stude service manuals, I know they tried hard. Studying the two hydrovacs, regular and disc brake versions, there is no mention of any significant difference between the two or that the residual check valve in the M/C should be removed in the disc brake set up. (In the discussion of the operation of the calipers, there is mention of the absence of a residual pressure check valve. Makes me wonder how the rears are set up. I know they are different in the 64 Hawk. I would expect a residual check valve is needed to prevent fluid drain back but can't find it in any text or picture.) There is pretty much a one-for-one match of all the components. The only real difference I can see is in the 'end cylinder' which is longer and thinner and does not incorporate a bleeder screw.

                      Comment


                      • #12
                        Avanti's used a vacuum booster between the pedal and master; unlike the Hawks. There is no residual pressure valve, or check valve, in the stock arrangment. The rear cylinders are small,(3/4"), to make them more compatable with the front discs, and prevent rear wheel lockup.
                        I converted to the Avanti II style dual circuit master, and have a residual pressure valve for the rear only.
                        I know a firewall mounted fluid reservoir was optional on Hawks. Did they use that to take care of the drain back problem?
                        Mike M.

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                        • #13
                          That's why the rear brakes are significantly different on a factory disc brake Stude as opposed to a drum brake Stude. With the mechanical eccentric adjusters (one for each shoe) near the top of the shoes, the retraction spring can only pull the shoes back so far before they hit the stops that the adjusters represent.
                          This also means regular rear brake adjustments (there's no self-adjusting provisions) for optimum brake performance.

                          Miscreant at large.
                          No deceptive flags to prove I'm patriotic - no biblical BS to impress - just ME and Studebakers - as it should be.

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                          • #14
                            There was no need for the Studebaker shop manual to mention removing a check valve. The two brake systems used different master cylinders. The appropriate master cylinder either had or didn't have a check valve, as needed. It is when people start mixing brake system parts that they experience difficulty. Also, keep in mind that the rear drum system on factory disc brake cars is different than the rear drum system on all drum brake cars. I have owned various combinations and worked on many more. The system that I prefer on Studebakers is an all drum system without power assist. The main thing is for all components to be in excellent shape.
                            Gary L.
                            Wappinger, NY

                            SDC member since 1968
                            Studebaker enthusiast much longer

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                            • #15
                              Studegary, I agree with your comments on mix and match and the requirement to keep everything in good shape. The problem is that the front drums on my Hawk are beyond their service limits and I have yet to find new ones or used ones that are not being sold at out of sight prices. I intend to drive my car and put significant miles on it, so I did not want to constantly be in the hunt for replacement drums. That is why I got Mr. Turners kits (dual m/c and front discs).
                              Do you have a line on new finned front drums?

                              Lew in Escondido, CA

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