What actually causes a flywheel or clutch explosion ?
If I avoid the causes, I'll be fine with an aluminum bellhousing.

Is it RPM ?
Is it parts that have small but growing cracks ?
Is it heat ?
Is it a HEAVY clutch/flywheel ?
Clutch engagement too violent ?

All of the above, I would guess.
What else ?

I have the installation instructions for a Hays clutch I bought in '83... it said that a flywheel with cracks can come apart from the torque applied to it ("and not RPM as is commonly thought", or something like that...)

Why not just get the scattershield and then not have to worry about your feet staying attached...

Buddy of mine had a piece of flywheel come through the side window of his car right behind his head. It came out of a big block Chevelle they had changed clutch and flywheel in between rounds. He figured they had gotten in a hurry and left flywheel bolts loose. Chevelle had an aluminum bellhousing.

I put pieces of clutch disc through an aluminum bellhousing on my small block Chevelle when the lining came off during a downshift.

Another vote for a scattershield.

Are you feeling lucky?
AKA aside a lot of the stock GM and Ford flywheels are cast iron, most early Mopars flywheel s are either cast steel or forged steel
On your deal I would use a SFI certified steel or aluminum flywheel along with a SFI certed clutch and pressure plate if your feeling lucky.
If your not feeling lucky buy all of those parts and a good scatter shield also
I saw Bob Lambecks B/MP 1968 hemi Baracuda after he exploded a SFI pressure plate with a good SFI legal scatter shield, it flatten the scatter shield almost flat, parts of the pressure plate pierce the front bars in the roll cage in front of the firewall, the inside floor was flat tore up and I think it broke his right foot also. He had another car built after that and always used the block plate after that also, he had told me I didn't need to use the block plate on my 1970 hemi Cuda A/S hemi 4 speed car. I put it back on the next clutch change
I've broken a early cast steel bell housing due to a driveline vibration and over revving the motor in 3rd gear, NOT GOOD

Good buddy of mine bought a 68 Charger RT440 4speed in 69. It was their only car for years. Typical hot rod/ street racer/ family car in those days. Delegated to a second car when the time came but still street raced. It was about 1981 when was driving it back from picking up his kid from school. No hot roding at all. He just let the clutch out in second gear and the oem flywheel exploded. Fortunately, he had a used scatter shield from a local Pro Stock team. He had left off the block plate,though. Broke all the ears off the tranny, took a chunk out of the block and the shifter almost broke his leg. He said it sounded like a bomb went off.

From fist hand experience. I was standing next to a Chevy nova with a small block and a 4 speed at a burnout contest. The engine was rev'ed and the clutch dumped. The engine rpm went up, car sounded exactly as it should. I looked to the rear tires, the one that I could see on my side of the car, and it was even moving. The car, within seconds, started smoking from the under the car in the clutch area, then bam! The damage was insane, I won't go into all the little things I saw but the rear crank flange was where the dist used to be and the tranny with shifter attached had spun it the car many times ripping the floor open. I looked at a piece of the flywheel in impregnated in the asphalt, looked cast to me by the grain structure. My takeaway from this was (because at the time my weekly bracket car was a 4-speed) , correctly or not, was diaphragm clutches suck, cant even spin a street tire without slipping, and never have a cast flywheel. I soon acquired a Lakewood bell housing and Hayes billet flywheel. I know many will disagree with my assessment but it has served me well and I am sticking with it.

I agree with the need for steel flywheels and scatter shields. Diaphragm clutches have improved a lot since those days. I have no problem getting sideways in my 451 Dart (with a Centerforce dual-friction diaphragm clutch). And you bet I have a Lakewood with the block plate and a steel wheel


(This may have been an automatic, but the principle is still the same).

Not long ago a friends Hemi street car exploded a clutch. No blow shield, he had floored it leaving a show, linkage hung up on those new holly bowl bolts (cross ram), engine (solid lifters) was screaming (about 5 seconds) till he cut the ignition, no rev limiter, the levers that holds the steel plate to the cover where ripped off. Don’t know why it didn’t come out. I ground the carb bolt so it wouldn’t hit again, something to check if you’re using the old cross ram and new Holly’s. All Centerforce parts
Mine will have the block plate and blow proof, I like my feet the way they are!
I’ll add, my opinion is that RPM is the number one cause for explosions, read up on how the forces double or more with each thousand RPM

You would be guessing correctly. Don't do any of those things and you should be safe. I would also add cheap, non-SFI rated parts. After recently seeing the results of a pressure plate explosion at maybe 9K, I can tell you it's not something to take lightly.

OK thank you gents, all good examples. Of course, I can't argue against safety.

I know I posted here in the race section.

All that said, millions of cars drive around with aluminum bellhousings just fine. What I was hoping for
is to discuss more the causes of extreme failure, explosions.
It sounds like there may be a bit of a random chance element at work here, but likely only if the parts
in question have been previously abused and not replaced. Anything can be abused ! So what's the definition
of abuse ?
I'm using a billet aluminum flywheel but have not picked a clutch yet. I have no intention of sidestepping
the clutch at 7000 just for fun. Not that I would drive like Grandma, but let's just say I intend to show respect
to the machinery.

I know this is like asking "How many runs on aluminum rods ?" One less than when they broke.

Why not let the clutch pedal fly at or above 7000 RPM
I have and like it a lot, 8600 RPM is better yet when you get the all your ducks in a row to race like that

I love it too! First time I drove a buddies 4 speed car I asked him what RPM he left at. He said he didn't know, just hold if to the floor. Valve float will stop it.