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Vortec V6 Flywheel question

Discussion in 'Builds and Fabricators Forum' started by Sgt_jarhead, Nov 2, 2015.

  1. Nov 2, 2015
    Sgt_jarhead

    Sgt_jarhead Sponsor

    Fallbrook, CA
    Joined:
    Sep 23, 2015
    Messages:
    183
    I acquired a 2000 or 2001 Chev Vortec 4.3 V6 I plan on stuffing into my '42 MB to replace the 67/68 Chevy 153 cu.in. 4cyl under the hood. I need to purchase a flywheel for the Vortec as it is currently bolted to an auto trans.

    My question is, Can I use a 168 tooth flywheel from the V8's on my V6? As long as it is the "one-piece seal, right tooth count, external vs internal balance, etc?" Reason I ask is because the V8 flywheels seem to be quite a bit heavier (45 vs 30lbs) than the V6 counterparts. My line of thinking is that a heavier flywheel and harmonic dampener will increase torque a little and (more importantly) allow me to have a much lower idle speed (looking for something in the 450-500 rpm range). The engine will power a SM420 and Dana 18 with the 1:3.15 gear set from Novak. Or am I completely off base?

    Pulling the 153 in the morning, and need to have the new engine in and running by March.
     
  2. Nov 2, 2015
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
    Sep 23, 2002
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    12,529
    Yes, as long as all the requirements you mention are met. The V-6's were frequently used in smaller vehicles like S-10's and the like. Since the vehicle was lighter they could reduce the diameter, size, and weight of the flywheel, reduce the diameter of the bellhousing, and hence reduce the size of the transmission tunnel inside the vehicle giving more cabin space.
     
  3. Nov 2, 2015
    tarry99

    tarry99 Member

    Northern California
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    3,784
    SGT,

    The Heavy Flywheel cannot "ADD Torque" per se as the engine does when it creates horsepower. For lack of a better word , We sometimes call that Inertia induced Torque. The Heavy Flywheel can only add inertia as it spins and is then loaded. The application of the load to the spinning mass uses that Inertia to increase Torque Momentarily. After that Kinetic energy is spent or absorbed only the Torque of the engine is now available again. At that moment, the extra mass of the Heavy Flywheel now becomes a liability as it begins to absorb a portion of available engine torque output to re-accelerate the mass once again......................

    Low gears obviously help the motor accelerate the mass at low speeds..........where you will see a noticeable lack of power will be when shifting up through the gears and also when trying to accelerate in High Gear while perhaps passing a vehicle at freeway speeds................

    With the Granny low transmission and a 3.15 gear set in the Transfer case , notwithstanding what ratio's you have in the axles............you already have a huge gear multiplication in Low gear for low speed.
    Having said that , I would personally forgo the need to also pack around the extra weight of a heavy flywheel.
     
    Last edited: Nov 3, 2015
    Sgt_jarhead likes this.
  4. Nov 2, 2015
    duffer

    duffer Rodent Power

    Bozeman, MT
    Joined:
    Sep 17, 2009
    Messages:
    4,460
    Yep and the V8 flywheels are not necessarily heavier. A stock GM small block 400 flywheel weighs 27.6 lbs. I'm running a 25lb Hays version behind the 381 in my 3B and have no problem putting along over just about anything at 500 rpm in low range.
     
  5. Nov 2, 2015
    Sgt_jarhead

    Sgt_jarhead Sponsor

    Fallbrook, CA
    Joined:
    Sep 23, 2015
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    Ok. I keep looking into it. The flywheel I was looking at on Summit was 45lbs but only listed it for V8 applications. The V6 ones all seemed about 30lbs. The weights were for cast iron nothing fancy flywheels. I have no desire to spin this motor past 5,000 rpm, really don't want to be above 4K for any period of time.

    Currently running 4:88's on 31" tires, to be upgraded to 33's after the motor swap. Also will be adding an overdrive to assist with the freeway cruises.
     
  6. Nov 2, 2015
    scott milliner

    scott milliner Master Fabricator

    Seattle Wa.
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    Dec 17, 2002
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    2,361
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