Flex Plate instead of Flywheel ?

Discussion in 'DIY Marinizing' started by Jango, Mar 20, 2006.

  1. Jango
    Joined: Aug 2005
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    Jango Senior Enthusiast

    Can an Automatic trans Flexplate be used instead of a flywheel with a Velvet Drive Trans?

    I realize proper Engine balance must be maintained, but can't see why the "Damper" couldn't be bolted to a proper flexplate instead of the heavier flywheel. Flexplates have thicker steel than Dampers, so strength shouldn't be an issue.
    Am I missing something?

    Anyone with any expierence with this? Thanks
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Automatic transmission flexplates are bolted to the flywheel.
     
  3. Jango
    Joined: Aug 2005
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    Jango Senior Enthusiast

    Gonzo,
    Flexplates take the place of a conventional Flywheel. They have a Ring gear and a full surface to which the Torque converter is attached. NO additional FLYWHEEL is used. The flexplate attaches directly to the Crankshaft and has additional balance weights in the case of an Externally balanced Engine.

    I have installed many Flexplates and Auto Transmissions.
     
  4. Steve H
    Joined: Aug 2004
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    Steve H Senior Member

    It's been done. The problem is that the lighter weight of the flexplate will lower the rotational inertia. Engine might be more likely to die when putting in gear. Also if your prop comes out of the water then engine will over rev alot quicker. Other than that it will sound alot cooler when you rev it up in nuetral at the dock!

    Steve
     
  5. Jango
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    Jango Senior Enthusiast

    Thanks Steve, I guess I forgot what the purpose of a Flywheel is.
     
  6. fasteddy
    Joined: Jul 2006
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    fasteddy Junior Member

    You need the flywheel mass. Flexplates substitute torque converter mass for flywheel iron, but the total masses are close to the same. You need the mass not only as described above, but also to cushion the driveline from the power pulses.
     
  7. hartley
    Joined: Feb 2006
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    hartley Junior Member

    flexplate instead of flywheel

    fasteddy ...spot on mate .......Gonzo ????????
    cheers
     

  8. fasteddy
    Joined: Jul 2006
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    Location: gainesville ga

    fasteddy Junior Member

    I have personal knowledge of at least one instance in which the flexplate was no longer bolted to the crankshaft flange, but still drove the torque converter, and the FJ55 Landcruiser down the road. Got me over 1k miles home and safe. Lots I don't like about bowties, but the things are pretty tough.

    IIRC, the 377 is a 400smallblock with a 350 crank and and .010overbore, and the 383 is a 350 block with a 400 crank and rods and special deck height pistons. the former is an rpm (read HP) motor, and the 383 is a torque monster. And has the advantage of being available as a stock 4bolt main block. There were only a very few 4 bolt main 400 blocks, of which I own one. I've read that less than 200 were cast/machined.

    If I were doing the GM block swap, I'd go ahead and spend the $ to have a 400ci block machined for splayed 4bolt mains, forged/nitrided crank, Hbeam rods, Mahle forged pistons, and a Crane roller cam and lifters, with neddle bearing rockers with tip rollers. Milodon or gm big block oil pump. FI based off aftermarket high flow parts for gmTBI, controlled by a potted MegaSquirt2, with ford EDIS ignition. I'm leery of boat turbochargers, so if I forced the induction, I'd use one of the low pulse rootes blowers or a centrif. with water/air intercooling. I'm playing with a refrigerated water/air intercooler, but unless the boat already has engine driven a/c, it's too much bother for a boat. I figure 475ftlbs n/a, and 550-600 if blown, with at least 80% of that available from 1200-5500rpms. Oh, yeah, cam helical gear drive instead of chain....
     
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