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Clutch master cylinder volume

Discussion in 'Manual Transmission & Clutch' started by davisw73, Nov 2, 2020.

  1. davisw73

    davisw73 Junior Member

    Posts:
    5
    Likes Received:
    3
    Joined:
    Jul 1, 2014
    Location:
    Central Florida
    First Name:
    Davis
    Truck Year:
    1985
    Truck Model:
    C20
    Engine Size:
    6.5 banks turbo diesel, NV4500
    So here's my dilemma. I have an 85 C20 that I am converting from TH400 to NV4500. I have stock 85 hydro master cylinder and 99 NV4500 internal slave. I have everything mounted, ready to go and it seems the square body master doesn't seem to push enough volume to completely disengage the clutch. I have it completely bled and have plenty of travel left in pedal. I can see the throw-out bearing immediately start to move as soon as I push the pedal and I can force a very small feeler gauge in between the friction disk and pressure plate, but when I turn the output shaft the clutch is still fairly engaged and drags bad enough where the only gear I can turn it in is 5th (doesn't turn motor).
    Am I wrong on my theory about volume or is there something else I'm missing? Is this common and I missed it in the 30,000 threads I read about this conversion? Is there a bigger bore master that everyone uses that bolts in with minor mods? Can a 99 master be adapted to my 85 firewall without a ton of mods?
    Thanks,
     
  2. bucket

    bucket Super Moderator Staff Member

    Age:
    39
    Posts:
    23,116
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    9,529
    Joined:
    Aug 3, 2010
    Location:
    Usually not in Ohio
    First Name:
    Andy
    Truck Year:
    '77, '78, '79, '84, '88
    Truck Model:
    K5 thru K30
    Engine Size:
    350-454
    How much stroke do you have on the master cylinder rod? I'm wanting to say that max travel is just under 1", but can't remember for certain.
     

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