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Technical Flathead Clutch and pressureplate, 11"

Discussion in 'Traditional Hot Rods' started by AULIZ, Feb 16, 2016.

  1. AULIZ
    Joined: Oct 28, 2005
    Posts: 824


    I bought bigger part used, old Ford Flathead parts. There was big clutch and pressure plate.
    280mm = 11" OD and bolt circle is approx. 12.5". Where they have used these "huge" cluches?


    Attached Files:

  2. Jet96
    Joined: Dec 24, 2012
    Posts: 966

    from WY

    Usually in trucks. Hay haulers, dump trucks, etc. Sometimes in heavier cars (Merc) by the 50's . The ones I've got came with a heavy duty transmission with PTO cover on the side.
  3. AULIZ
    Joined: Oct 28, 2005
    Posts: 824


    Thanks. Never seen clutch like that.

  4. lowsquire
    Joined: Feb 21, 2002
    Posts: 2,564

    from Austin, TX

    i have 11" truck clutches in both my flathead cars. Mercs had 10" clutches. they are damn solid and dont slip although there is a weight penalty.. i think the pressure plate and clutch plate are about 6-8 lbs heavier than the 9" units. you can machine the flywheel more than this to get it bac down under 9" clutch weight. contrary to popular myth the pedal effort is no higher with the big clutch if the factory pedal/lever ratios are maintaned.
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  5. Petejoe
    Joined: Nov 27, 2002
    Posts: 10,170

    from Zoar, Ohio

    Using a 11" in my little pickup. But its important to not use the pressure plate. Your left leg will thank you. I rebuilt my pressure plate with weaker type springs.
    Last edited: Feb 16, 2016
  6. Mart
    Joined: Mar 3, 2001
    Posts: 3,631


    The French and German motors were fitted with 11" clutches. At least any one I have seen had them. Makes sense, I suppose as they were all truck motors.

  7. image.jpg I found an 11 in clutch in a 1948 f5 big truck used to haul firewood up and down the Colorado mountains.I have run 9 in clutches (lighter) in all my big inch FLATMOTORS and even in my first Anglia that ran high 14 's at over 90 mph with never a hint of slippage!
  8. Ron Plumlee
    Joined: Feb 12, 2012
    Posts: 107

    Ron Plumlee

    Just for what it's worth, I have had a pretty experienced machine shop refuse to cut any more 10 inch Merc flywheels down.....the have had one blow up in balancing and one blow in a car, seems where they take the meat out (pressure plate side) weakens old flywheels that are already stressed from years of pressure and use. They will chop other flywheels, but not the 10 inch Merc.

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