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Thread: flywheel vs. flexplate

  1. #1
    Senior Member
    Join Date
    Feb 2009
    I've senn both in jet boats, what's the advatanges of a flywheel and advantages of a flexplate in jet boats? Thanks!

  2. #2
    Senior Member
    Join Date
    Feb 2009
    Irvine, CA
    I've senn both in jet boats, what's the advatanges of a flywheel and advantages of a flexplate in jet boats? Thanks!
    Either will work ... it'll just change you drive shaft length or motor placementif you change from one to the other due to the thickness difference ...
    a flexplate will RPM the motor faster due to less weight on the reciporcating assy ... but a flywheel gives a more accurate balance (so I've been told) ...
    Again, this is what I have been told ... I have seen data to prove the RPM difference ... but no data on the balance issue ...

  3. #3
    Flexplates are weak compared to a flywheel the reason being that a flexplate is made rigid with the use of a torqe converter in a car with an automatic transmission. I always use aluminum flywheels.

  4. #4
    Senior Member
    Join Date
    Apr 2010
    Flywheel may have less run out on the ring gear than the flex. Ive ran both, have had problems with the alum. flywheels cracking near the PTO but they have zero run out unlike the flexplate.

  5. #5
    A heavier flywheel will keep some momentum in the engine. This is good in some auto applications like a road race coarse...but a lighter flexplate or alum flywheel helps the engine rev up/down faster and helps with throttle response...

  6. #6
    WOW! I was going to ask this question today!
    I have been looking for a replacement engine for my olds455 and I see a lot of 454 engines for sale locally but all of them are out of automatic cars and trucks. I thought I HAD to have a flywheel on the crank! Now that I know I don't NEED a flywheel, I think I'll grab one of them 454's. But I just bought a crankshaft to finish my Olds 455 buildup so I'll work on that first. The 454 will be a forced induction winter project. Rock on!
    PS: I've fired up a small block chevy after engine swap and I forgot to bolt the torque converter to the flexplate, YES the RPMS come up INSTANTLY.
    I'm just a little concerned about low RPM, heavy load ignition timing when not using a flywheel. Maybe I'll get the biggest harmonic balancer I can find.

  7. #7
    502 JET
    Which ever you choose to run make sure you have the proper length bolts for the pto adapter or drive shaft if its a direct bolt up. Too long or too short of bolts is not a good thing.

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