Gents,
Is anyone willing to share info and experience about their choice of flywheel spec for FE's? I currently am using 32lb. steel on a 427 sized SO with Toploader and 3:31 gears. The cam makes power from 3500 to 7000. I took 3lbs. off the nose of the crank by switching to an Innovators West balancer on the advice of Geo. Anderson and noticed improved throttle response and am very pleased. Wondering if I should go to aluminum flywheel to further improve response, or if even this "small"size motor [not a big stroker] needs heavier "flywheel effect".
Thanks for any thoughts you might share.
Cobra Make, Engine: I used to fix them for a living
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The lighter the flywheel the better. If the motor can idle, the flywheel is heavy enough.
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Cobra Make, Engine: 66 COBRA FE 427 /4SP. (HCS Coupe w/ 408 Stroker and TKO 600 -sold)
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I just ordered a new aluminium flywheel with a steel contact surface from Red at McCloud along with a new pressure plate and kevlar clutch. Fly wheel will weigh about 16 pounds. The whole set up cost me about $700.00. Haven't received it yet so I can't tell you how I like it but it was going to ship this week.
Clois
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I recently upgraded from my stock stroke 351 to a 427 Windsor stroker. My first engine had a new billet steel flywheel and my new motor has an aluminum flywheel. The difference is quite amazing. The new motor revs like an Indy racer. Add a solid cam and BG carb and wow! I'm impressed!
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After a good hard ride.....oil pressure is over 50, temp is below 190, she idles and no new dents. LIFE IS GOOD!
OK...My 428SCJ (externally balanced) was balanced with a steel flywheel. I was thinking of changing to a aluminum one however I get mixed answers to the question of "Do I need to rebalance the entire engine or can just bring my existing flywheel to a machine shop along with the new aluminum one and have him match the balance?"
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Cobra Make, Engine: Contemporary CCX33868 Sold. Just "playin' the boards now."
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As usual, Mr. Fixit hit it right on the head, without mincing words.
The lighter the better is true up to a point. If the engine will idle is part of it. What this means in plain english is, the same cam will idle rougher with a light flywheel than with a heavy one, because of the dampening effect of the extra weight. Simple. It takes more energy to move more weight. Therefore, the crankshaft rotation is not disturbed (slowed down and speeded up) by the misfires caused by a lumpy cam.
Now, with that said, the other part is plain old driveability. Simply put, the higher the gear ratio, the more flywheel weight is needed for the car to move without the engine stalling when the clutch is let out.
Summation. 427 in 2,300# car 3.xx rear gears, 20-25# for street, 15-20# for track. An ultra light flywheel is great for throttle response, but miserable to drive on the street in traffic.....even in a light car like a Cobra.
In my case, I used billet steel on the advice of my engine builder who is also a pro racer. It was machined down from 40# to 25# and worked well on the street as well as the track with my 427 S/O and top loader with 3.54 gears.
I was warned NOT to go with aluminum as they have a nasty habit of coming apart on a bad day. On a good day, they will warp more quickly, because there is a difference in heat transfer from the steel insert to the aluminum disk.
What no one should EVER DO is use a stock cast iron flywheel in anything but a stock pickup. NOT EVER in a Cobra or other high performance car.
By the way, going from 3.54 to 3.31 won't make any appreciable difference in gas mileage, but it will make the car feel a little soggy at lower rpm's. I went from 3.73 down to 3.54 and was delighted. The car was plenty perky and much more driveable. Frankly, I wouldn't go to 3.31 from 3.54. I got real close to pegging my 180MPH speedo with the 3.54's. That was God's plenty for me!
Try the 25# steel flywheel. I really think you'll like it.
Al
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Cobra Make, Engine: I used to fix them for a living
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reguardless of what flywheel you pick
GET an SFI approved scattershield.
these little cars have enough gearing, enough torque, and light enough weight, that you won't have "tool light' a flywheel. If money isn't a problem, get one of those 8" multidisk setups, they are neat.
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In a fit of 16 year old genius, I looked down through the carb while cranking it to see if fuel was flowing, and it was. Flowing straight up in a vapor cloud, around my head, on fire.
Cobra Make, Engine: Home built, supercharged 544cu/in automatic
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As the various answers above indicate, the answer lies with what you want to do with your car and how you drive it. Steel vs. Aluminum? Heavy vs. Light? Some other things to ponder. You ever spin the wheel of bike in your arms then tried to turn it? You have to force it don't you? Now think of a car that goes around corners fast such as a Cobra. That big ol' heavy flywheel spinning at 4000 rpms and the clutch too, resists the turn bigtime. That's why most cornering race cars have smaller and lighter flywheels/clutches. Yes, a lightweight wheel will give you faster seat of the pants throttle snap too coming out of corners. But lets look at that one.
A heavy wheel gives you what is called "torque roll on" when you shift to a different gear. This, in effect, gives you a torque boost when you shift to a higher gear. In a close ratio tranny this effect is really not much of a factor and it may even be a hinderance, but in a wide ratio tranny it is important. It effects street tractability and overall performance too.
Torque roll on is important at the dragstrip because in almost ALL cases the heavier wheel will give you a better E.T. , to a point. The rule of thumb in drag racing is 10 lbs of flywheel weight for every 100 lbs of rear wheel torque your engine produces, up to about a 50 lbs flywheel weight. After 50lbs it's too dangerous to run more flywheel weight, even with a approved shield. Torque roll on is a bigger factor for heavier cars too vs. lighter cars.
Let's see, steel vs. aluminum. A aluminum wheel gives up heat much faster than steel. So if you are shifting a lot this will help clutch fade. On the other hand a steel wheel is stronger and resists harmonics much better, but they retain heat. A aluminum wheel is a bit more ticky tac to set up right, but in the case of 99.9% of the Cobras out there I would say aluminum is the right stuff to use. For my car aluminum wasn't right, when it was a close ratio stick.
Don't worry about aftermarket aluminum flywheels, they are on 2000 horsepower, 3000 lbs cars. Your car will not be a problem I'd bet.
Overall my advice on most Cobras- use a slightly heavier aluminum flywheel unless you have a close ratio box or road race a bunch.
cobrashock
Cobra Make, Engine: Home built, supercharged 544cu/in automatic
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Postscript - Very, VERY, important. Don't forget to check the torque settings of the flywheel bolts after you run a aluminum flyweel for a while. I can't emphasize this enough. Yes I know in most cases that means pulling the clutch. It would be a good time to check those pressure plate bolts/torque anyhow.
cobrashock
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Last edited by cobrashoch; 11-14-2003 at 09:29 AM..
I have an aluminum flywheel behind my FE and I love it. Car is light enough that I don't need the rotating weight to get the car moving. Motor revs like a small block and idles fine at 800 rpm (294S Comp Cam solid-605 lift)
I always wondered about compression braking beating you up too much with a big high comp motor and a light flywheel in a light car. I know that a light flywheel will allow it to rev freely, which is a good thing. Bu when you let off the gas, isn't it like tapping the brakes? That is that case with a high compression 4-stroke dirt bike with a light flywheel, e.g. a YZ 450F or a Cheney John Banks Replica (for the old schoolers). On a bike, it wears you out a bit getting thrown forward as soon as you let off the gas. A popular mod for the YZF is to add flywheel weights to allow the bike to carry a little momentum when you let off the throttle. It makes for a much smoother ride, but acceleration does not really suffer.
Cobra Make, Engine: Home built, supercharged 544cu/in automatic
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Lew - You hit the nail dead on the head, with a wheel that is too light. Makes a car a bear to drive on the street. On a road race car the light wheel will make your car a bit faster IF, I repeat, IF your good enough driver. But it's for sure no fun. Sometimes a heavier setup will also make you a smoother driver in fast turns. Compression braking is not a huge factor on the lower compression engines that most of the street Cobras use, esp. big blocks.
cobrashock
Gents,
My compression is
10.33:1, my cam is 110 deg. LCA, .613-.633", 244-255 dur.and the car is tracked occasionlly, if that helps anyone help me.
Thanks,
LIGHT vs. HEAVY FLYWHEEL
Linear Mode
