Flywheels, Bellhousings

[flipper35]

Quick question.

I have a small block and it is currently only putting out 420/430hp and in the neighborhood of 450tq.

It isn't a lot of stress on the flywheel, but it is the stock, cast 47# unit. My concern is that the flywheel is even with your thigh, just above the knee where you sit in the car.

So my question, should I be concerned? If so, should I get a certified SFI flywheel or both SFI certified flywheel and bellhousing. If I do the bellhousing the flywheel has to come off so I might as well replace it. I would replace it with a lightweight if it weren't externally balanced, though I imagine Brewers can weight it for me. Or if it is a concern, can I just get a local shop to weld 3/8ths hardened steel for the inside of the tunnel? I don't really care about the road.

Bellhousings are a bit pricey, but I could resell the stock one for about half according to what is currently on FleaBay.

You seldom hear of it, but I know two people that had a flywheel fly apart. One had a chunk in his ankle and one had a large chunk go up through the dash and cowl and departed to who knows where. Both were muscle cars of the good old days. Both GM branded.

[legion]

You can also get a Kevlar blanket to put over the transmission.

[flipper35]

For an auto you can, I have yet to see one now for an a833 or any other manual.

Many years ago there were flak jackets available for manuals though and I don't know what happened with them.

I saw a couple of exploded flywheels and torque converters back when I was drag racing. They can be really nasty. I personally would not want to put that much torque through a stock flywheel without some sort of shielding (sorry--not expert enough to recommend specifics). But I'd also likely go with an upgraded flywheel. Shielded or not, a disintegrating flywheel is a violent thing.

[flipper35]

I have another small block in the garage for the car that should be in the neighborhood of 485hp/525tq. That will have a better bellhousing, flywheel and harmonic balancer for sure. Just not sure if i need to upgrade before that is done.

(the stock rubber strip balancer tends to slip on quick reving engines)

[masraum]

I would install a scattershield (bellhousing).

[908/930]

How hard are you driving it? What RPM are you hitting?

I would install a scattershield just for insurance.

[flipper35]

I generally don't go past 6000 rpm. Peak torque is at 4300/4500 something like that and peak hp is 5700 rpm. It isn't the RPM as much as torque applied that makes them fail. Or so I am told.

That said, since it is a toy it gets driven hard every time I drive it even if it is just to work.

[masraum]

My dad had a buddy that blew a clutch/flywheel. Lots of energy in them. I hear part of one of them went in the bottom of his leg near his foot and came out the top of his knee. I suspect that would make a pretty big mess.

[JackDidley]

Originally Posted by madcorgi

I saw a couple of exploded flywheels and torque converters back when I was drag racing. They can be really nasty. I personally would not want to put that much torque through a stock flywheel without some sort of shielding (sorry--not expert enough to recommend specifics). But I'd also likely go with an upgraded flywheel. Shielded or not, a disintegrating flywheel is a violent thing.

Me too. Be safe. A good bell housing can save your limbs.

[Arizona_928]

Originally Posted by masraum

I would install a scattershield (bellhousing).

+1

Drag, and other racing orgs/events require these....


Watch some LubeTube videos of flywheels taking for flight at the drag strip. They have enough power to clear through your femur like butter...

[Geoz1]

Originally Posted by flipper35

Quick question.

I have a small block and it is currently only putting out 420/430hp and in the neighborhood of 450tq.

It isn't a lot of stress on the flywheel, but it is the stock, cast 47# unit. My concern is that the flywheel is even with your thigh, just above the knee where you sit in the car.

So my question, should I be concerned? If so, should I get a certified SFI flywheel or both SFI certified flywheel and bellhousing. If I do the bellhousing the flywheel has to come off so I might as well replace it. I would replace it with a lightweight if it weren't externally balanced, though I imagine Brewers can weight it for me. Or if it is a concern, can I just get a local shop to weld 3/8ths hardened steel for the inside of the tunnel? I don't really care about the road.

Bellhousings are a bit pricey, but I could resell the stock one for about half according to what is currently on FleaBay.

You seldom hear of it, but I know two people that had a flywheel fly apart. One had a chunk in his ankle and one had a large chunk go up through the dash and cowl and departed to who knows where. Both were muscle cars of the good old days. Both GM branded.

I have seen, and know people who have experienced clutch/flywheel failures. It's not pretty. With that said, a scatter shield is good insurance, if you like your car and lower limbs. I doubt you are dumping the clutch at every light, with slicks in a car that hooks. So I doubt you need a SFI bell or flywheel.

I have gone low 10's in 5.0 mustangs, numerous GM 4 speed cars, all with slicks and stock flywheels and bell housings. Once you put a clutch in that "locks up", then look at upgrades.

As far as the harmonic balancer, Yes, they move under extreme situations. For a street car, stock is fine. If you want to spend the money, go with a Fluidampr, or an ATI. Both will need to be honed to fit your crank snout.

[asphaltgambler]

Unless you are drag / street racing with sticky DOT tires it's really not necessary. If the flywheel was in good condition to start with - you'll be fine.

The times I've seen a failure is when the stock unit was used in high horsepower / high RPM applications - which isn't wise to begin with.

If you want to replace it, then yes - go with both a quality flywheel that's external balanced to fit your engine and a good bell housing.

With much experience - I can say I would never install a lighter weight flywheel in anything other than a road race vehicle - and even then it would depend on the class. I have installed a few in several NA engines and 1 small displacement turbo 4cyl and made the driving experience awful. If anything - it was slower on the street.

[flipper35]

The last set of tires were Goodyear Blue Streaks. The next set will probably be Avons.

[flipper35]

The flywheel was brand new. Has 10k miles on it now.

[sammyg2]

Originally Posted by asphaltgambler

Unless you are drag / street racing with sticky DOT tires it's really not necessary. If the flywheel was in good condition to start with - you'll be fine.

The times I've seen a failure is when the stock unit was used in high horsepower / high RPM applications - which isn't wise to begin with.

If you want to replace it, then yes - go with both a quality flywheel that's external balanced to fit your engine and a good bell housing.

With much experience - I can say I would never install a lighter weight flywheel in anything other than a road race vehicle - and even then it would depend on the class. I have installed a few in several NA engines and 1 small displacement turbo 4cyl and made the driving experience awful. If anything - it was slower on the street.

^^^^^ agreed.

If you are worried about a flywheel coming through the floor of a fairly mild hot-rod, you should prolly keep it in the garage.


Kinda reminds me of my old flatbottom boat.
The short driveshaft was bolted to the front of the engine inside the lower blower pulley, and the other end was connected to the V-drive right beside my thigh.
It was covered by a thin aluminium tube that didn't do much except keep beach towels out.
If one of those U-joints let go it could have cut me in half.
Note the engine was (mostly) a supercharged 417 Donovan built about as far as it could be taken and revved to over 6000 rpm on occasion. Never dyno'd it but it was way up there. HP was prolly close to four figures on racing gas.

When I decided to go IHBA drag racing, the rules required a very thick and heavy steel tube be installed around that driveshaft.
Either that or a lightweight titanium unit that I could not afford.

Never needed it before or after, but rules are rules.

I also had to install a whirl-away ratcheting device on the prop shaft to comply with said rules, that one saved by arse.
Without it I would have likely flipped the boat at around 120 mph.

[flipper35]

Now, the short driveshaft I don't worry about. It is 8" long.

[sammyg2]

LOL, you win

[sammyg2]

Not mine but similar to what I had:

[flipper35]

I was told to put a CV joint in. I think they were joking.