Zacctly, any motor will "wind up" a little quicker with a lighter flywheel, be it steel or aluminum......I doubt the average guy could really tell the difference, probably looking a a few tenth's of a second.........Unless your all out racing, there is no need for the extra expense of an aluminum flywheel....IMHO of course......

And I have 2 Mustangs with one flywheel of each,I driven both quite a bit........

BTW: there are steel flywheels out there that are almost down to the aluminum weight for about 60% of the price of an aluminum wheel.......

David

The motor winding up faster is not just some interesting anecdotal side effect. If the engine winds up faster when running full throttle in gear as it will with an aluminum flywheel, that means the car is accellerating faster. It is a waste of hp trying to spin up a 30lb disc from 1,000 rpm to 6,500 rpm as fast as possible. It takes a lot of HP that could be going to the rear wheels. It is a parasitic loss. Think of all the time, money, and effort spent in building up our engines for maximum power. The $100 differnece to get an aluminum flywheel over steel of cast iron is a small price to pay for 1/2 second off your 1/4 mile times as indicated in one of the posts above, or for blowing off the competition on the street. It is free hp that is no longer being wasted trying to rotate a 30lb mass.


.

I wont dispute the above graph showing 1/2 second in the quarter mile runs, but look at the dates on the graph, one year apart.....Assuming all things were the same, that's some big gain....I'd have to get more info on the car, yes, it had the same engine, what what about tires, were they the same, weather conditions, same or not, weather alone will play a factor in 1/4 times. driving will also.... One could assume the driver was a better driver a year later and that alone could account for some of the lower ET.......

I've run both flywheels on the street and on a road race car as well as a dirt track car and never saw more than 2/10's or so better times......definetly something you could not feel by the seat of your pants.......

The original question was what to put in the car, "This car is a street roadster recreation and will be strictly street driven by me."

For that use, I'd still recommend a steel flywheel.......JMHO of course....

David

I agree w/David - pick a lighter weight steel version. Instead of deciding between an aluminum and a steel flywheel, decide whether you want a light or a heavy flywheel. There are vast differences between the different brands, from a featherweight 12-15 lbs to 40 or more. You can't just narrow it down to the two materials they're made from. Given the fatigue characteristics of aluminum vs steel, I'd pick a lightweight steel one every time over an aluminum one. Ask your builder what the weights are for the brands and materials you're considering.

Right now I have 2, 65 Mustangs, one is a 3200 lb. street car with a standard/stock steel wheel, 3.25 rear gear ratio, I can putt-putt around town in 2cd and 3rd gear at 1000 rpms all day with no problems, no jumping/bucking/spitting/caughing, that car is a pleasure to drive....

The other is a 2700 lb. road race car,3.70 rear gear, 13 lb. aluminum wheel and I can't putt-putt around the paddock in 2cd or 3rd gears at 1000 rpms, it'll buck and kick eveytime.....I wasn't going to put an alum. wheel on that car till the machine shop offered me a brand new one still in the box for 100 bucks, I couldn't pass up that deal......seems they had that and a few other parts along with a block they machined for a guy that never came to pick up his parts nor pay the bill, so the shop was selling off the stuff to recoup money.....

back in my dirt track days we tried an alum. wheel, the car did come off the corners a little crisper, then the track outlawed alum wheels, so we expiremented with taking weight off stock steel wheels... We were running a small block Chevy at the time and you could get stock steel flywheels at any junkyard for 5 bucks a piece.....we had 5 to 8 at one time....we drilled a bunch of holes in some and in one, we turned it down on a lathe and then drilled holes in it and got it down to 12 pounds....I was afraid it would explode, cause it was soo thin and didn't want to drive the car with in it.....I split seat time with a buddy and he drove the car with that wheel the last half of the season with no problems/failures........

I WOULD NOT recommend to anyone to do what we did, it was down right crazy/stupid and dangerous, but we were young and bullet proof, or so we thought....

Normally, small block steel wheels weight in around 30 pounds, aluminum from 12 to 15 depending on brand, I've seen some new steel wheels advertised in the low 20 pound range and to strike a happy meduim, I would use a lightweight steel wheel for the reasons DougD listed above.........

David

Isn't a steel flywheel about $250 and an aluminum flywheel about $500? Assuming that's about right, isn't worth getting an aluminum flywheel for additional $250? Makes sense to me in a Cobra.

EDIT: It seems to me, and maybe only me, that when building an FE, the $250-$300 or whatever is just a "rounding error."

As I recall, my RAM unit was about $300 about 2 years ago from Jegs. In a light car like a Cobra it makes a huge difference. In a heavier car, not so much. I putt around at 1,000 rpm all the time, very smooth. Take off from lights just off idle, no reving or problems.


.

I can do a RAM steel flywheel (for an FE) for about $275, or a PRW steel flywheel for an FE for $225.

For aluminum needs, I usually push the Fidanza. It has all pressure plate patterns and is the lightest (14lbs) between RAM, McLeod, and Centerforce. I can do it for $350.

For small block cars, I have some awesome deals on steel wheels.

So, $75-$125 difference. Hmmm. %/

Sorry, I should have given more information. The red line is also about 45 more HP at the wheels. This generally would make things a bit more exagerated, but even with another 45 HP at the wheels it is more in control than a steel flywheel with less power to use.

Nothing about stuffing a 600+hp engine in a 90" wheelbase car weighing sometimes as little as 2400 lbs. with no top or side impact bars, no airbags and very little driver protection to start with makes much sense to me........:):););):LOL::LOL::D:D

but that's part of the thrill of having a having a car like that!!!!!!!!:D:D

In the grand scheme of things when spending big bucks for a car like a Cobra, a couple of hundred extra dollars is nothing......:LOL::LOL:

it all boils down to whats best for the engine combo and the way the car will be used...

David

The Kirkhams have been putting their car on a diet for a long while. With the aluminum rear end, Quicktime bellhousing, aluminum flywheel, and an all-aluminum FE, their cars are under 2,150 lbs.

I talked with several FE engine builders before I picked one, but not one of recommended a steel flywheel.

There doesn't seem to be a clear consensus here. The light car - light flywheel rationale makes simple sense. I guess I will go with the aluminum flywheel as recommended by the builder.

Thanks for the responses.

there might not be a clear answer but there is some good information and opinions along with some hard facts. In any case it has me thinking hard...

I've always used the formula one pound of flywheel for every 100 pounds of car. So a 2400lb Cobra would dictate a 24lb flywheel. Once again, it's the weight, not the material it's made from.

So then in a 4,300 lb Cadillac CTS-V you would need a 43 lb flywheel????:cool: The factory flywheel is 26 pounds.

My son's 03 SVT Cobra Mustang came from the factory stock with a 17 lb aluminum flywheel and that car weighs 3,700+ lbs.


.

Opinions are all over the board on this. I just offered one.

So why the difference in relative weights on the two cars you listed, in your opinion?

the 03 Cobra Mustang is (was) a very high performance car from the factory. Ford put an aluminum flywheel on it from the factory because high performace cars run faster/better with lightweight flywheels. Just as an fyi, it also came from the factory with an aluminum driveshaft for the same reasons, . . . less rotational inertia to drain horsepower trying to spool up = a faster more high performance vehicle.


.

I first drove my 427 in 1994. The engine was and still is 427 cubic inches with a standard stroke crank. The original build used a steel flywheel that weighs 40+ pounds. At the beginning of this Cobra ownership I always thought my engine wound up a little on the slow side when I blipped the throttle for a downshift. I just figured it was normal.

Around the year 2000 I changed the clutch, pressure plate and flywheel. The new flywheel was an over-priced Center Force aluminum unit and weighs about 20 or 22 pounds. What a substantial difference that unit has made.:eek: Throttle response is noticeably faster. The engine has felt as though it spools up quicker at full throttle. The aluminum unit is a keeper for my car.:MECOOL:

The original steel flywheel is still hanging on the wall in my work shop.

David

well there ya go !!!

.