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Flywheel heat cracks #3048387
06/06/22 04:58 PM
06/06/22 04:58 PM
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God's Country Maryland
GODSCOUNTRY340 Offline OP
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How bad do heat cracks have to be before the flywheel is not usable?

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Re: Flywheel heat cracks [Re: GODSCOUNTRY340] #3048399
06/06/22 05:53 PM
06/06/22 05:53 PM
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That would, imo, depend on the application.

Some would say any, I have run with them though in a stockish street only application.

Some sort of 1000 hp race car, zero would be my answer.

If it's a 130 tooth flywheel a new one is under $75 at Rockauto LUK LFW215

the 143 tooth one is alot more, PIONEER FW161

Re: Flywheel heat cracks [Re: Sniper] #3048455
06/06/22 09:12 PM
06/06/22 09:12 PM
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Originally Posted by Sniper
That would, imo, depend on the application.

Some would say any, I have run with them though in a stockish street only application.

Some sort of 1000 hp race car, zero would be my answer.

If it's a 130 tooth flywheel a new one is under $75 at Rockauto LUK LFW215

the 143 tooth one is alot more, PIONEER FW161

iagree
And will also mention that some claim the heat spots that "disappear" after turning are actually still there and can cause issues with a new clutch and PP. shruggy
If they are that visible after turning, myself i would scrap it. twocents

Re: Flywheel heat cracks [Re: GODSCOUNTRY340] #3048487
06/06/22 11:52 PM
06/06/22 11:52 PM
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A few shallow in 1 location, maybe not to bad.
If they encircle the flywheel, I'd scrap it.
Wider the crack, good indicator of depth also

Re: Flywheel heat cracks [Re: GODSCOUNTRY340] #3048502
06/07/22 02:16 AM
06/07/22 02:16 AM
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Take it to a competent shop and have it turned, surface on a flywheel grinder to remove them.
All Mopar flywheel are either cast steel or forged steel, not cast iron like Ford and GM are downscope up
Much stronger and will take a lot more abuse before failing boogie up

Last edited by Cab_Burge; 06/08/22 02:56 PM.

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Re: Flywheel heat cracks [Re: GODSCOUNTRY340] #3048508
06/07/22 05:21 AM
06/07/22 05:21 AM
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I would not run that on a public highway.

The sudden failure of that part could “startle” the driver to such an extent that someone in another vehicle could be killed.

Using that part in off public road racing,
where parts are stressed near and past their limits and higher risk assumed with limited money, might be different.

Re: Flywheel heat cracks [Re: GODSCOUNTRY340] #3048526
06/07/22 07:36 AM
06/07/22 07:36 AM
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Originally Posted by GODSCOUNTRY340
How bad do heat cracks have to be before the flywheel is not usable?


Did you sand or dress up the flywheel? It's strange to have heat cracks with no evidence of overheating. As to the public being in harm's way from a flywheel failure, that would be your last concern if that comes through the floor pan.

Oh, BTW, I would not run that flywheel if the rest of it has that pattern. Multiple radial cracks in such close proximity aren't good. I'd wager that if you checked that with dye penetrant it would look like an alkali flat.


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Re: Flywheel heat cracks [Re: 6PakBee] #3048735
06/07/22 08:11 PM
06/07/22 08:11 PM
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If that was mine I would replace it.

Re: Flywheel heat cracks [Re: 57Fury440] #3048869
06/08/22 10:47 AM
06/08/22 10:47 AM
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Originally Posted by 57Fury440
If that was mine I would replace it.


Same here , how much are your feet worth? I don't reuse old heat checked flywheels , a billet flywheel is cheaper than a wheelchair ...


running up my post count some more .
Re: Flywheel heat cracks [Re: GODSCOUNTRY340] #3049017
06/08/22 08:38 PM
06/08/22 08:38 PM
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Originally Posted by GODSCOUNTRY340
How bad do heat cracks have to be before the flywheel is not usable?




This shouldn't even be a discussion, buy a quality SFI approved flywheel.......

Re: Flywheel heat cracks [Re: DAYCLONA] #3049021
06/08/22 08:50 PM
06/08/22 08:50 PM
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Originally Posted by DAYCLONA
Originally Posted by GODSCOUNTRY340
How bad do heat cracks have to be before the flywheel is not usable?




This shouldn't even be a discussion, buy a quality SFI approve flywheel.......


Why? Is this the race forum? Nothing wrong with a OE replacement type flywheel.

Re: Flywheel heat cracks [Re: Sniper] #3049030
06/08/22 09:40 PM
06/08/22 09:40 PM
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We didn't really establish application so tough to call. High winding small block? Race application? Street car? I've turned wrenches my whole life......sent many flywheels like that to be surfaced and put them back in service. Can't recall any of them coming back to bite me in the ass. Most were just daily driver apps though.

Re: Flywheel heat cracks [Re: JohnRR] #3049767
06/11/22 07:10 PM
06/11/22 07:10 PM
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Originally Posted by JohnRR
Originally Posted by 57Fury440
If that was mine I would replace it.


Same here , how much are your feet worth? I don't reuse old heat checked flywheels , a billet flywheel is cheaper than a wheelchair ...


My feet are worth as much as my Lakewood scattershield. But I agree, I wouldn't run that one - by the time you get done paying the machine shop, you could buy a new one twocents

Re: Flywheel heat cracks [Re: 360view] #3049836
06/12/22 07:40 AM
06/12/22 07:40 AM
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You could spend 10 hours a day seven days a week studying cracks in materials
from age 18 onward,
and still only “know” a fraction of what experiments have hinted at.

You can start studying cracks in iron/steel alloys
but when you have to switch to cracks in rock samples in a lab
it gets 10X harder.

Then it gets 10x harder if you need to deal with “real” rock cracks underground.

If you study and use explosives
or high voltage electricity
you can begin to feel somewhat comfortable and fear lessens a bit.

The more you study cracks
the lessening of fear never comes.

“Flint knappers” who lived 250,000 years ago were the first crack experts.

Re: Flywheel heat cracks [Re: Sniper] #3049927
06/12/22 12:25 PM
06/12/22 12:25 PM
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Originally Posted by Sniper
[quote=DAYCLONA][quote=GODSCOUNTRY340] Nothing wrong with a OE replacement type flywheel.
B.S. OEM stock iron flywheels will explode if damaged and rev over the limit that they will fail at, around 4500 RPM shock
I've seen it on stock GM and Ford street cars puke whiney
Steel is not as prone to explode as iron flywheels are, hence the advent and success of the after market racing flywheel industry up scope

Last edited by Cab_Burge; 06/12/22 12:25 PM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Flywheel heat cracks [Re: Cab_Burge] #3049940
06/12/22 01:26 PM
06/12/22 01:26 PM
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Originally Posted by Cab_Burge
Originally Posted by Sniper
[quote=DAYCLONA][quote=GODSCOUNTRY340] Nothing wrong with a OE replacement type flywheel.
B.S. OEM stock iron flywheels will explode if damaged and rev over the limit that they will fail at, around 4500 RPM shock
I've seen it on stock GM and Ford street cars puke whiney
Steel is not as prone to explode as iron flywheels are, hence the advent and success of the after market racing flywheel industry up scope


There is a reason we don't drive Fords or Chevys. Extrapolating from a different manufacturer is a great way to go wrong with confidence.

Pretty sure I've wound up stock Mopar flywheels well past 4500 rpm with zero failures on multiple occasions in multiple vehicles. The only reason there is an aftermarket RACING flywheel industry is because of the SFI requirement. Nothing more, nothing less and since this isn't the RACING forum here one has to assume we are talking about a street car. SFI is a liability modifier and a way for the track, the sanctioning body and the racer to cover themselves if something happens and someone in the stands is hurt.







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