Are hairline "cracks" in flywheel a concern? - Chevelle Tech
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post #1 of 13 (permalink) Old May 29th, 03, 11:02 PM Thread Starter
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I have an opportunity to purchase a #3789733 flywheel, to add to my 4 speed conversion parts, for a reasonable price. The flywheel has small hairline cracks on the surface side that are mostly towards the center. It will need to be surfaced.

Are these "cracks" normal in the casting of the flywheel?

Should I avoid this flywheel?

Thanks for any help.

Rob
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post #2 of 13 (permalink) Old May 30th, 03, 1:37 AM
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MOST PROBABLY, after it is surfaced, it will be just fine for a street/mild performance engine. If you plan to SERIOUSLY buzz it on a frequent basis-------------------don't use it. I have used flywheels MANY times with small surface cracks such as you describe----------------------never a problem. But I'd never put one in a race motor.

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post #3 of 13 (permalink) Old May 30th, 03, 9:21 AM
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Beware of cracks, especially around the bolt area. Don't think you can put it together and not have to look at the cracks again, You may see them as the flywheel comes through your floorboard!!!
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post #4 of 13 (permalink) Old May 30th, 03, 9:27 AM
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Yeah, you "may" be alright, but I personally wouldn't take a chance to save a few bucks...I mean, if that thing does 'blow', it's gonna cost quite a bit more to fix, esp. if it's your leg
Maybe after you surface it, you'd be alright...might be worth checking that out at least...
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post #5 of 13 (permalink) Old May 30th, 03, 11:02 AM
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If you were in a pinch and couldn't afford a better flywheel, then maybe okay, but I wouldn't, unless you have a scattershield...

There are some parts you just should skimp on, for safetys sake... For a performance car, a nice flywheel and blow-proof bellhousing are two of those, IMO...

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post #6 of 13 (permalink) Old May 30th, 03, 11:08 AM
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nope..... I wouldn't use it [img]tongue.gif[/img] the amount of money saved wouldn't be worth what it cost me in worry when I dropped the clutch at 6,000 .. of course it could get you a good start on that convertable top you've allways wanted

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post #7 of 13 (permalink) Old May 30th, 03, 1:13 PM
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If they scare you into tossing the flywheel into the trash can, I'll take it off of your hands!

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post #8 of 13 (permalink) Old May 30th, 03, 2:42 PM
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I picked up a used flywheel that had cracks on the surface, but not near the bolt holes. I think those are just spots where the flywheel got really hot from friction. On mine, the cracks were shallow and there was a small amount of discoloration around the cracks. After a $35 resurface job, the flywheel looked good and works great. I'm not worried about the flywheel scattering. But, then again, I don't run my motor up to high rpm's, dump the clutch or hard shift it.
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post #9 of 13 (permalink) Old May 30th, 03, 4:04 PM
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Quote:
Originally posted by 67mlbu:
I have an opportunity to purchase a #3789733 flywheel, to add to my 4 speed conversion parts, for a reasonable price. The flywheel has small hairline cracks on the surface side that are mostly towards the center. It will need to be surfaced.

Are these "cracks" normal in the casting of the flywheel?

Should I avoid this flywheel?

Thanks for any help.

Rob
Quote of the Day: It's cheaper to buy NEW parts than to buy NEW feet.

I would avoid it, and get a new one, steel SFI if possible. And seriously consider a scattershield if you don't already have one.

take care,

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post #10 of 13 (permalink) Old Jun 2nd, 03, 11:51 AM Thread Starter
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Tom-

If I don't take it, he has someone else already interested.
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post #11 of 13 (permalink) Old Jun 2nd, 03, 11:57 AM Thread Starter
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Tom-

If I don't take it, he has someone else already interested.
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post #12 of 13 (permalink) Old Jun 2nd, 03, 1:54 PM
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It comes down to whether you are going to use the flywheel for normal street use or put the flywheel through hard use. GM, Ford and Mopar sold millions of cars with cast iron flywheels and aluminum bell housings. As far as I know, with all those cars out there, flywheel and bell housing failure has never been a problem for normal street use. Steel safety equipment is nice, but not essential for non-race use.
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post #13 of 13 (permalink) Old Jun 2nd, 03, 2:17 PM
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For a mild street engine that will not see engine speeds above 5500 - 5800 RPM, it will be just fine. Those cracks probably appear to be spread from the center outward. They are caused by the inertia of the rotating mass. The metal actually expands and contracts ever so slightly as the engine speeds up and slows down. The result is those tiny, hairline cracks in the surface of the flywheel face.

Of course, if there are cracks around the bolt holes (which I bet there aren't) it should not be used.

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