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Old 05-01-2002, 12:46 AM   #1
GrandSportC3
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Default flywheel or flexplate?

That may be a stupid question but I would like to know exactly what the difference between a flywheel and a flexplate is.
It is my understanding that a flexplate is used in combination with automatic transmission and a flywheel is used for a manual transmission. Is this correct?
Why are flywheels much more expensive than flexpates?

thanks

Olivier
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Old 05-01-2002, 01:38 AM   #2
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Default Re: flywheel or flexplate? (GrandSportC3)

My understanding was always that a flexplate is for an Automatic tranny, and a flywheel is for a Manual. But, when looking to buy people don't always use the same terminology, so be sure to check.
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Old 05-01-2002, 01:51 AM   #3
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Default Re: flywheel or flexplate? (GrandSportC3)

Flywheels are for manual transmissions they're weight can vary greatly depending on the material - billet steel, cast iron, aluminum.

Flexplates are used exclusively for automatics and are generally a piece of stamped steel with a ring gear welded on.

Like all car parts quality varies widely.

Price is obvious, which is cheaper , a 35 pound slab of billet steel or a stampied piece of 10 gauge galvanneal with a ring gear weldedonto its curcumference.
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Old 05-01-2002, 08:33 AM   #4
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Default Re: flywheel or flexplate? (fauxrs)

>>Flywheels are for manual transmissions they're weight can vary greatly
>>depending on the material - billet steel, cast iron, aluminum.
>>Flexplates are used exclusively for automatics and are generally a piece of
>>stamped steel with a ring gear welded on.
>>
>>Like all car parts quality varies widely.
>>
>>Price is obvious, which is cheaper , a 35 pound slab of billet steel or a
>>stampied piece of 10 gauge galvanneal with a ring gear weldedonto its
>>curcumference.

Thanks for the information! However - I have one more question:

When I purchased a "external balanced" engine for my 69 (sold) I had to use another flexplate because the engine was a 383 instead of a 350.
Is this the same way for flywheels or can I use my current flywheel when purchasing a engine with a different size crank (externally balanced)?

Thanks

Olivier
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Old 05-01-2002, 10:35 AM   #5
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Default Re: flywheel or flexplate? (GrandSportC3)

350 engines are internally balanced ( 0 balance) while 383 engines are externally balanced (offset or out of balance). I'm not sure if I'm using the right terminology here but a 350 engine requires a flywheel or flexplate that is in perfect balance (0) while a 383 engine, due to the use of a 400 crankshaft must have a flywheel or flexplate that is offset balanced by a certain number of ounces. I believe the reason for this is because the larger pistons in a 400 engine would require crankshaft counterweights that are too big to be accomodated by the engine case. The flywheel or flexplate for a 383 or 400 engine typically has a weight welded to it to throw it out of balance the correct number of ounces. Like everything else there are exceptions to the rule. You can get a 383 or 400 assembly that is internally balanced through the use of heavy metal (Mallory metal) and then use a zero balance flywheel or flexplate. Flywheels and flexplates also come in different sizes and different tooth counts (153 vs 168) that require different starter nosepieces. This just keeps life interesting. :)


[Modified by vettfixr, 9:38 AM 5/1/2002]
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Old 05-01-2002, 11:10 AM   #6
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Default Re: flywheel or flexplate? (GrandSportC3)

[QUOTE
When I purchased a "external balanced" engine for my 69 (sold) I had to use another flexplate because the engine was a 383 instead of a 350.
Is this the same way for flywheels or can I use my current flywheel when purchasing a engine with a different size crank (externally balanced)?

Thanks

Olivier
[/QUOTE]

On any externally balanced engine you will need the correct balancing device at either end of the crank - since your 383 is based on a 400 crank - externally balanced - you will need a harmonic balancer from a 400 and a flywheel or flexplate from a 400.

Internally balance motors use neutral balanced componants so a 350 flywheel/flexplate should NEVER be used on a 400 crank. Also know that the newer 350s, I dont remember where but starting perhaps with the LT1 in the c4 vette are also externally balanced.
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Old 05-01-2002, 11:10 AM
 
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