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flex plate question ?

Discussion in 'The Hokey Ass Message Board' started by hugh m, Apr 24, 2013.

  1. hugh m
    Joined: Jul 18, 2007
    Posts: 2,142

    hugh m
    Member
    from ct.

    Been looking for a flexplate for the motor going in my T, a Pontiac Super Duty four cylinder, with a real unusal crank flange. It dawned on me that i have a couple of Quartermaster 7" multi disc flywheels lying around,( I think they are forgings), that fit. The question is would it be practical, and safe to machine off the clutch facing and use one for an automatic transmission flexplate? Would there be stress risers from the lathe that would be detrimental? Any real world info would be appreciated,is it a dumb idea or what?
     
  2. steel rebel
    Joined: Jun 14, 2006
    Posts: 3,604

    steel rebel
    Member Emeritus

    I'm not an expert but flex plates need to flex. If not they can put so much pressure on the engine crank that it will push it forward and burn the bearings.
     
  3. hugh m
    Joined: Jul 18, 2007
    Posts: 2,142

    hugh m
    Member
    from ct.

    Thanks for the reply, makes sense.
     
  4. fanbelt
    Joined: Apr 10, 2007
    Posts: 27

    fanbelt
    Member

    there is a adapter for pontic super duty to chevy crank pattern, I think I got mine from Gehart in calf. years ago. Have seen them on ebay.
     

  5. hugh m
    Joined: Jul 18, 2007
    Posts: 2,142

    hugh m
    Member
    from ct.

    How does it work, a ring of some type? What ring gear and starter do you run? Thanks.
     
  6. black 62
    Joined: Jul 12, 2012
    Posts: 1,895

    black 62
    Member
    from arkansas

    do flex plates really flex when in use ? if so,why ? thanks...
     
  7. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,059

    dreracecar
    Member
    from so-cal

    I run a .500 thick steel "flexplate" on the back of my Bln Alc SBC dragster without any problems, REACTOR prod makes a aluminum flexplate that some of my customers run. Chuck up the converter on the oil pump driver and make sure that the mounting pads are square to it and when you bolt it all up together, make sure the converter has 1/8 freeplay before you bolt it to the plate
     
  8. hugh m
    Joined: Jul 18, 2007
    Posts: 2,142

    hugh m
    Member
    from ct.

    Do you see any problems running a machined down flywheel as a flexplate?
     
  9. fanbelt
    Joined: Apr 10, 2007
    Posts: 27

    fanbelt
    Member

    mine is made to use a chevy ujoint as they are easer to find than a pontiac pattern should work with a flexplate. although I haven't used it that way.
     
  10. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,059

    dreracecar
    Member
    from so-cal

    Anything can be done , the question is can you?

    Is what you have big enuff to fit the converter bolts?
    Is there enuff space on the backside for converter bolts?
    What about the starter ring gear?
    How do you plan on holding it in the chuck?
    Will there be enuff suport to keep it from singing when making a cut?
    What about the bolt down holes for the converter?

    Mondello performance will make any size/type of flexplate and if it has to be SFI'd they can do that too---
     
  11. hugh m
    Joined: Jul 18, 2007
    Posts: 2,142

    hugh m
    Member
    from ct.

    Thanks for the replies, I'm gonna pull the trans apart and check things out tonite.
     
  12. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,263

    Atwater Mike
    ALLIANCE MEMBER

    GREAT reference, DIVCO. Hope everybody watches, good info. This is what causes old flexplates to crack, making some 'mechanics' diagnosis of con rod brgs./broken pistons/etc. bogus. (BOGU$$$)
     
  13. 55yak
    Joined: Nov 5, 2011
    Posts: 41

    55yak
    Member

    Hugh M, you would be amazed at the difference in lateral run-out between a flywheel (between 1 to 5 thousands) and a flex plate for an automatic trans. If you set up a dial indicator on the flex plate you will see run out that would be unacceptible on a flywheel. A flex plate flexes and that is ok. I found that out when I switched from an old 55 Hydro with it's torus assembly hooked up to a steel flywheel to a flex plate bolted to a more modern overdrive 700R4.
     
  14. hugh m
    Joined: Jul 18, 2007
    Posts: 2,142

    hugh m
    Member
    from ct.

    Thanks for all the replies guys. Just ordered a Tilton super duty four starter nose from ebay, and as soon as I can verify it will work with the 142 tooth ring gear that I have, will order up a SFI flexplate from Reactor. These Super Duty fours are pretty neat, especially for a T, but some of the parts are really hard to find these days.
     

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