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'63 GT Hydrovac

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  • Brakes: '63 GT Hydrovac

    Here is a picture of the hydrovac on my stock '63 Hawk GT R2 with factory disc brakes. It is, I believe the hydrovac for drum brakes not disc's. The car is the first or second '63 Hawk built (63V1640). Does anyone know of a similar situation? Did Studebaker just use an older model hydrovac off the shelf or what? Randy Bohannon

    HerClick image for larger version

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  • #2
    That appears to be the same unit im my 63 G Hawk w/front disc. I just recently had mine rebuilt by Ed Strain in Florida.
    My sn # is 63V21818, built in January 63. I don't believe the hydrovac was used in drum brake applications.


    • #3
      Yes it was used with drum brakes.


      • #4
        The early disk brake cars were fitted with the Drum Brake HV. The Type A 'Vac was generally inadequate and the Type F later replaced it. There was a service bulletin and kit issued to upgrade the Type A to a Type F for those owners who complained.. The Type F has a .750 power cylinder vs a 1.0 for the Type A. Line pressure was increased from around 600 to 900 psi with the retro fit.
        64 GT Hawk (K7)
        1970 Avanti (R3)


        • #5

          Yep, the disc brake booster has a smaller slave cylinder for higher boost presssures.
          Bez Auto Alchemy

          "Don't believe every internet quote" Abe Lincoln


          • #6
            Thanks for clearing that up 64V-7K. I knew that mine was a type F, but wasn't clear on the distinction and couldn't find written anywhere the line pressure, though i;ve been told it was 600, good info.!Click image for larger version

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            • #7
              Bob - Can you give me any info on that service bulletin and kit for upgrading a Type A to a Type F HV? I'd really like to see it. - Randy


              • #8
                I'll have to look thru a few things. Will keep you advised..

                and voila!

                The part number for the D.B. Hydrovac itself, is 1558380, Type F.
                The part number for the Disk Brake Hydrovac unit (REPAIR kit) is number #1559734
                The Service kit to change Type A Hydrovac to a Type F is Studebaker part# 1565515

                The part number for 63/64 Drum brake Hydrovacs is 1544394, Type A.
                The Drum brake Hydrovac Repair Kit is #1541846

                I don't have the service letter..
                Last edited by 64V-K7; 02-12-2015, 12:36 PM.
                64 GT Hawk (K7)
                1970 Avanti (R3)


                • #9
                  The car is the first or second '63 Hawk built (63V1640).

                  How do you figure that? I think serial numbers started with 63V1001. Your's is over 600 cars "down the line" after the first one.


                  • #10
                    Originally posted by mbstude View Post
                    The car is the first or second '63 Hawk built (63V1640).

                    How do you figure that? I think serial numbers started with 63V1001. Your's is over 600 cars "down the line" after the first one.
                    I think he meant first or second Hawk with the AVANTI brake package, not the first or second Hawk.


                    • #11
                      I had the booster done on my '64 GT w/disc by Ed Strain in FL. The only problem I had was leakage at the copper washers. Ed was a phone call away and advised me to try new washers and sealer. I got replacements at NAPA and things seem fine for now. As for parts he may be able to help you with that upgrade. He can be reached at 800-266-1623. I would also try any number of vendors listed in TW.
                      Rob in PA.


                      • #12
                        Did you use a thread sealant as well as a different crush washer?
                        Must be a common thing, both washers leaked!
                        Last edited by BrianC; 02-17-2015, 05:50 PM.


                        • #13
                          Stude Intl has a kit (#1655515) which will convert a type A hydrovac(drum) to a type F(disc). The kit was for dealers to increase boost from 600psi to 900psi on early hawks that got the type A with disc brakes. Randy


                          • #14
                            Follow up on Hydrovac for my '63 GT R2: I replaced the type A (drum type) with a type F (disc type) using the existing banjo etc fittings. Everything bolted up just fine and the system works perfectly. However, the new type F unit from SI leaked from both banjo fittings (used new copper washers). Finally figured out that the threads were not square with the sealing surface. After squaring the threads and washer surface by filing the surface, no more leaks!