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Old 03-13-2011, 09:16 PM
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Cast flywheel safe for street use?

I'm putting a manual trans back in my truck. It's a 72 GMC with twin turbo 327, makes maybe 500?hp. I bought a lakewood safety bellhousing for it and I already have the clutch and flywheel in it and read the instructions where it says a cast flywheel is not recommended.
I haven't drag raced it, but I wouldn't mind making a couple passes just to see what it runs. It's intended to be street driven and it sees about 6000 rpm say 6500 to be safe. I am running a stock style luk clutch and a gm cast flywheel followed by a super t-10.
The only reason I got the lakewood bell was after watching a youtube video on a clutch explosion. Is the lakewood enough for me or do I need an expensive flywheel too?
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Old 03-13-2011, 10:45 PM
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No offence but why do you think the instructions say that a cast flywheel is not recommended?? ...your legs.
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Old 03-13-2011, 10:57 PM
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I assumed it was to meet the sfi spec that is available to it. I don't need to meet the standards as I don't race a class. I only bought the bellhousing this year as extra insurance. I'm just trying to get a handle on where the line is I guess.
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Old 03-13-2011, 11:00 PM
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The Lakewood will protect your feet/legs

But not the back of the engine when the flywheel comes apart.
I would go ahead and pull the trigger and buy the correct flywheel.

CHEAP INSURANCE
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Old 03-14-2011, 07:49 AM
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Get the correct flywheel and be safe. I think that you knew the answer to your question before you posted.

Vince
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Old 03-14-2011, 08:14 AM
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Ive been 'disabled' most of my life...I'll gladly trade for a week to see how much you like it.

Seriously though, if you have the scratch for a TT327, buy the correct flywheel. They stock new flywheels...not new feet or legs, of course you might get lucky and it would let go and shred the motor. This is still cheaper than reconstructive surgery...but not as cheap as an approved flywheel.
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Old 03-14-2011, 04:32 PM
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I don't have "the scratch" for another flywheel, which is why I asked the question. Perhaps you could lend me one because you own autogear?
It seems to be a split camp, some say it's fine some say its good insurance, some of you are up in arms that I even asked the question. I asked the local machinist what his thoughts were, he's been around alot of years building race stuff. His words were"as long as your not launching it with slicks or sticky tires its fine, theres alot of cast flywheels out there". He recommended a scattershield for a clutch explosion.
I took it further and called mcleod, the bellhousing manufacturer. The gentleman said yes we recommend a billet flywheel. I told him what the machinist had told me. He said "I would agree with that as well, but why trust it to chance".

I'm conflicted because I've run this setup for 4 years, 3yea as a 4 speed. Last year I sold all the 4 gear stuff to go automatic and hated it. Instead of spending 300 on a 621 bell I spent 350 on a scattershield for extra insurance, now it seems to have opened a can of worms.
I'm curious, what do you all feel is the rpm limit for the cast flywheel? Maybe I'll just set the rev limiter to that?
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Old 03-14-2011, 05:12 PM
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Under normal RPM's up to about 6000 the cast flywheel will be fine. What happens when your at the top of second gear at 6000 rpm and you miss third? The tach swings wildy toward 7000 rpm before you can even react and BOOM.

Vince
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Old 03-14-2011, 05:20 PM
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Ok thanks that makes sense. Would I be in the clear if I just set the rev limiter to 5800?
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Old 03-14-2011, 05:31 PM
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Quote:
Originally Posted by 71/454
Ok thanks that makes sense. Would I be in the clear if I just set the rev limiter to 5800?
Sure, it would only swing to 6800 if you missed 3rd then.
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Old 03-14-2011, 06:18 PM
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And what about the innocent bystanders?

While I was working for a Michigan dragstrip. A 55 chevy blew a cast flywheel. Took out the back of the block. Ended up in the stands where it killed a 14 year old boy. Son of a local business man.

Another time, as a spectator at a different strip. Another 55 chevy blew a wheel. No shield, because it was "Just a street car". Took out the dash, windshield. Went several hundred feet into the air and landed on the hood of a newer chevy sedan. Piercing the hood and ending up wedged between the exhaust manifold and steering.

Back in the sixties I was in attendance at a street race. The local hot shot was a 61 Corvette. Lost a flywheel going into second gear. Severely damaged the hood and front fender. Blew a tire and ended up in the window display of a furniture store..

GET THE WHEEL!!!!!!!
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Old 03-14-2011, 06:30 PM
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Quote:
Originally Posted by BOBCRMAN@aol.com
And what about the innocent bystanders?



Another time, as a spectator at a different strip. Another 55 chevy blew a wheel. No shield, because it was "Just a street car". Took out the dash, windshield. Went several hundred feet into the air and landed on the hood of a newer chevy sedan. Piercing the hood and ending up wedged between the exhaust manifold and steering.
It has a shield, I understand what your saying though. This was the reason I got the blowproof bellhousing in the first place, I surely don't want to hurt anyone else, I guess I thought any clutch or flywheel explosion would be contained inside the bellhousing, but you all seem to be saying it wont be.
The funny thing is every billet flywheel is sfi spec. However that high dollar centreforce dual friction clutch everyone is running is not sfi approved, they are intended for STREET cars.
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Old 03-14-2011, 06:32 PM
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Quote:
Originally Posted by SSedan64
Sure, it would only swing to 6800 if you missed 3rd then.
I've never actually rattled it off the rev limiter, it will really go 1000 over?
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Old 03-14-2011, 07:12 PM
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What is the source of your current flywheel? Newer parts are made of better materials.

I have used many of the GM stock 15lb flywheels in oval race cars and turned them 7500RPM for years and have never had a flywheel fail. I have seen a few covers fly apart. That lightweight piece may not be the way to go a drag car.
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Old 03-14-2011, 07:17 PM
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Quote:
Originally Posted by lmsport
What is the source of your current flywheel? Newer parts are made of better materials.

I have used many of the GM stock 15lb flywheels in oval race cars and turned them 7500RPM for years and have never had a flywheel fail. I have seen a few covers fly apart. That lightweight piece may not be the way to go a drag car.
It's a stock cast GM flywheel I think it's out of a mid seventies truck.
What do you mean by covers, or lightweight piece? It's a standard flywheel, not lightened at all. The Bellhousing is an sfi spec from lakewood part #15000, and it's a street car.
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