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1990 6 speed flywheel Info Needed

 
Old 06-07-2019, 11:28 AM
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MR73
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Default 1990 6 speed flywheel Info Needed

Hello all,

I'm a new owner of 90 vette with a 6 speed ZF manual. I know these transmissions originally had a dual mass flywheel from the factory. I was already planning on changing to a single mass. After pulling the engine I discovered the factory flywheel had already been replaced with a single mass unit. Here's where my questions concerns begin.

1. I've read that some of these conversion single mass flywheel kits are too thick (around.100") if this is true what should the correct thickness be?
2. Is there a way to identify what type of flywheel I have by just a picture? I've searched it and I have not found any part numbers anywhere on it.
3. The engine going back into the car is an internal balance. I was told by the machine shop to just remove the external weight on the flywheel. I don't believe that is going to be "correct". The three threaded holes where the balance weight was attached will cause the flywheel to be too light on that side now. I'm I right?
4. This engine will be around 475 to 500hp so would I be OK even using this flywheel? If not, What brand steel flywheel would be a good choice?

Thanks in advance for any help you can give.






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Old 06-07-2019, 11:38 AM
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mtwoolford
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Originally Posted by MR73 View Post
Hello all,

I'm a new owner of 90 vette with a 6 speed ZF manual. I know these transmissions originally had a dual mass flywheel from the factory. I was already planning on changing to a single mass. After pulling the engine I discovered the factory flywheel had already been replaced with a single mass unit. Here's where my questions concerns begin.

1. I've read that some of these conversion single mass flywheel kits are too thick (around.100") if this is true what should the correct thickness be?
2. Is there a way to identify what type of flywheel I have by just a picture? I've searched it and I have not found any part numbers anywhere on it.
3. The engine going back into the car is an internal balance. I was told by the machine shop to just remove the external weight on the flywheel. I don't believe that is going to be "correct". The three threaded holes where the balance weight was attached will cause the flywheel to be too light on that side now. I'm I right?
4. This engine will be around 475 to 500hp so would I be OK even using this flywheel? If not, What brand steel flywheel would be a good choice?

Thanks in advance for any help you can give.


the thickness issue is from back in the day when single mass flywheels were first being retro fitted; single mass for a ZF 6 speed, pull style clutch weren't available so the interim solution was to take a flywheel from a chevy / Pontiac F body with a T56 trans and shave 0'095" inch off the surface.
now there's multiple offerings. I'm sure you can have that flywheel balanced, but balancing $ and resurfacing $ might make more sense to get new.
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Old 06-08-2019, 11:50 AM
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SJW
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I'd agree that a replacement is in your best interests, given what you're working with. That wheel has some significant hot spots on it. I'd dump it and start fresh.

Live well,

SJW
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Old 06-08-2019, 01:24 PM
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bjankuski
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Remove the weight you will be fine, that is how they were designed. To be netural balance with the weight removed.
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Old 06-08-2019, 01:48 PM
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WVZR-1
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I'd think shop would suggest 'balance for confirmation' as mentioned in #2 - replace with another? Maybe weight a 'feature' you'd like to tweak! Hot spots - seems so!! What does the business side of the f'wheel look like? What weight? Shop I'd think have suggestions that could be considered valuable.
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Old 06-08-2019, 08:55 PM
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MR73
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Thanks for the replies. I'm leaning toward just purchasing a new flywheel that's a neutral balance unit. I'm sure this flywheel is nothing more than a stock replacement that's seen better days. If it would have had some type of part number to ID it to a good name brand I would go ahead and resurface it.
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Old 06-10-2019, 10:08 AM
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MR73
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Originally Posted by WVZR-1 View Post
I'd think shop would suggest 'balance for confirmation' as mentioned in #2 - replace with another? Maybe weight a 'feature' you'd like to tweak! Hot spots - seems so!! What does the business side of the f'wheel look like? What weight? Shop I'd think have suggestions that could be considered valuable.
Here's an image of the front. From the machining cuts around the perimeter it appears to be one from Carolina Clutch.

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