Buzz,

I am not uptight just confused. Our cars were about as identical as they could be but there was a noticeable difference in coming down on compression. We ran the same gears, 3:27, and the same carbs. His would accelerate a little faster than mine but not enough for him to get away from me. And the first time I drove in on the track I almost lost it in the first turn as I was used to mine slowing down faster than his did. We must have had some kind of fluke thing happen. Maybe I should have painted my flywheel aluminum. :LOL:

Ron :D

Well, your thread kind of got hijacked on the minor issue. In case enough hasn't been said about the bellhousing, consider this: it's not your toes that are in the line of the clutch assembly. It's more like your knees and lower legs. If you really, really want to save $300, you might want to do it somewhere else. Your clutch may never blow. You may never see a clutch blow even on a track day. But $300 is cheap to keep both of your legs, and possibly other body parts, and possibly the body parts of bystanders, intact and in place should it happen.

There are many places you can put that skimped $300 in later, when you have it and if you choose. It's hard to swap out a bellhousing and you're likely not to ever do it unless you're pushed to by track requirements or something.

Saw it happen at a track. People in the stands ended up hospitalized. In fact I think a person died.

Do ya feel lucky, punk? Well...do ya??

Here's a good quote from the Kirkham Assembly Manual thread (http://www.clubcobra.com/forums/show...2&postcount=49):

Quote:

Notice we use an aluminum flywheel. I HATE steel flywheels! The motor takes WAY too long to rev and which makes canyon driving much less enjoyable. -- David Kirkham

Da Kirkhams are aluminum junkies. :D

Steel vs. alum flywheels. SFI/BLOWPROOF VS. OEM.

Yes it's very noticeable.
In a performance application, Aluminum is better, period. Not arguable.
They rev quicker, they are easier on the brakes, allow for better engine braking, way nicer to install when laying on your back under a car.
In the old days of drag racing, it was thought that a steel (read heavier) flywheel had an advantage in getting a heavy car with low torque and slicks out of the whole better. They thought winding up the motor up and storing the energy. The slicks could absorb the shock load and put the power to the ground, reducing 60" times.
The reality is, that advantage is quickly overcome buy the alum flywheels lighter weight, which is a huge advantage over the remaining 97% of the race.
With street tires that extra stored energy aids in breaking the tires loose.

SFI/BLOWPROOF VS. OEM.

You only need to see it happen once. It's hard to believe how much destruction results. It is exactly like a big fragmentation grenade going off. Very loud bang, big flash, lots of sparks, large pieces of jagged steel flying in every direction. They blow huge holes in everything.
My personal opinion is that they should be mandatory in Cobras because of passengers position relative to the flywheel. Mid thigh is a bad place for a 10lb piece of jagged steel going a couple of hundred miles an hour to strike.
What is the cost difference? Maybe $200-$300? Worth it to me, but that’s your call.
Sure would suck to blow the leg off (or kill) you girl friend or child, because you were trying to save $300 on a $50k weekend toy.

Not me

Ok, I agree with all you said. I am not a drag racer but I go once in a while and I saw a 56 Chevy that was running a blown motor and he didn't have a blow proof bell housing. Everything blew about 1/4th of the way down the track and the guy almost had his right leg severed plus they found parts of the Clutch stuck in the dash. That was a long time ago and I made up my mind right then that I was going to put one on my car for road racing. I later blew a clutch but it wasn't anything like the drag car did. When we opened the inspection plate it seemed dust and parts fell out for 5 minutes.

Ron

I agree with having a blow proof bell housing.... I have tried both alum and steal flywheels back to back in my car. A while back I chipped a tooth on my stock steal flywheel. It would still start, but made a terrable grinding noise. Unfortunatly, I had to replace my starter and flywheel. It happened after a hot start with bad fuel and the timing too high. "kick back". Any way, I bought an alum flywheel to replace the steal one.

After changing I could notice a little difference in acceleration. Motor did spool up quicker. I couldn't pick up on any other differences. Only positive gains for me. I didn't notice any braking or downshifting or off the line differences. I would go alum from the get go if i were you. JMO

What's the typical weight difference between steel and aluminum flywheels for FEs?

My overpriced Centerforce Aluminum flywheel weighs 17 lbs. Steels will be in the upper 20's. OEM's in the 30's.

Its about 10lbs LIGHTER for and FE 28-30 VS 18-20

The majority of engine braking is a result of the carb butterflys being closed and you have turned the engine into a hugh vacuum pump. Diesels have far greater rotating mass and they require exhaust or engine brakes to assist in braking. In reality, the greater mass of a heaver flywheel will require more braking than a lighter flywheel.

Different tires can have a considerable affect on rolling resistance. Brake pad material can also have an effect. The fluid weights in the transmission, and rear end can also be a factor.

Then you can factor in the clearances in the engine, and the rest of the running gear.

Noticing a trend here? There are so many factors that can affect rolling resistance, that unless it's an absolute twin of the other car, right down to the tire pressure, there will be differences.

Perfect. Gimmie a blow proof housing and a steel flywheel! Thanks!

Silverback51 did you get tire pressure in there? Yep now I see it!

When in doubt go all out! The steel bell housing is an execellent idea.Especially if you regularly hit the rev limiter.I once saw a 69 Vette get cut almost in half at a drag strip when flywheel exploded.That one event made me a believer in blowproof housings.

Ron, does your friends car have manifold vacuum and do you have ported vacuum to the dizzy?. The ported vacuum with butterflies closed has lower timing while the manifold vacuum has higher timing. I have ported vacuum and I like the sudden deceleration which comes with 14* at closed throttle and also gives me lumpy idle:D
Lou