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Thread: Flywheel or Flexplate?

  1. #1
    I'm No Expert shaun's Avatar
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    I have a 454 that i am rebuilding to put back into my jetboat. today i was asked if i was going to be running a flexplate or flywheel and though "Well thats a good question". What do you guys run and why? I heard that a lot of people run flexplates because they are lighter and you can spin the motor to max rpm faster.
    So my question is, what do you run and why?
    Also, i'm not sure if i'm missing a peice to hook the drive shaft to the motor. Is there somthing special the shaft bolts to or does it just bolt right up to the flexplate/flywheel?

  2. #2
    Jungle Boy
    Flexplate - Lighter but needs to be checked every once in a while to make sure it has no cracks in the area around the adapter flange or ring gear.

  3. #3
    I'm No Expert shaun's Avatar
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    Also, should i go with a SFI certified flywheel/flexplate?

  4. #4
    Senior Member
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    absolutely SFI...

  5. #5
    I'm No Expert shaun's Avatar
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    Originally posted by Rexone
    absolutely SFI...
    Besides the fact of running a SFI no matter which one would you recommend Flex or Fly?

  6. #6
    Lookin for Liquid
    This is a very good question for the jet boat crowd and it would be my intention on a jet boat to only run a flex plate. When we do v drive motors, most of them have a cam with a substantial duration, therefore the heavier flywheel tames the idle down a bit and makes it more consistent at that RPM due to the absorbtion of the rotational weight of the aluminum flywheel. In a jet you have the same thing happening with the impeller turning in the water at idle and loading the motor a bit so if you ran a camshaft with taller numbers the water load would prevent excessive idle lope.
    Another area is the fact of the peak rpm range of a jet is usually lower than that of a v-drive and you would not have as much cam to cause you idling problems to begin with.
    Just my .02
    PS Mike is right as far as SFI due to the fact that these motors and the stock flexplates were originally intended for approx 1/2 the rpm that jet boats run

  7. #7
    I'm No Expert shaun's Avatar
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    searched ebay and found this, look good?
    http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW
    I'm running a 1970's 4bolt 454 BTW.

  8. #8
    Lookin for Liquid
    Wonder where it's made?

  9. #9
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    Shaun, if you're going to use a flexplate, buy a GOOD one! Two years ago I made the same choice of a flexplate over a flywheel. I bought a CSI flexplate(you can find them at Summit, Jegs, etc). It is a serious piece that is at least twice as thick as one of those cheap stamped stockers. It costs a lot but this is no place to be cutting corners or counting pennies. My machinist, a drag car and drag boat racer himself, was very happy with my choice.
    As far as the driveshaft is concerned, you will likely need a PTO(or "button") to connect it to the crank. The older style drive shafts that are a direct bolt on are pretty rare. If your shaft has four evenly spaced mounting holes, you will need the adapter. SInce there are two different shafts(1310 u-joints and 1350 u-joints) and the flexplate/flywheel decision, you should probably call Rex Marine, CP Performance or Lookin For Liquid(I think I saw some in your Dragboats.com ad ) for the correct part.

  10. #10
    I'm No Expert shaun's Avatar
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    I dont plan on cutting corners but some times you can find good parts on ebay for a better price. My main problem is i dont know what brands to look for, You recommended one brand, CSI, are there any others?
    I'm also looking for a good dampner! The block is at the shop and i need these parts before they can balance everything.

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