Lightened flywheel

[another69]

How do you know what weight flywheel to go with? Is there some kind of equation (weight, HP, gear ratio)? My car with a TH350 always had traction issues off the line, and now that I'm swapping to a TKO600 (which has a taller 1st), I'm thinking a lighter flywheel might be better.

[ProdigyCustoms]

Engine, weight, gear, tire size are but a few of the important thngs to consider. Most times a billet flywheel will weight in the 30 LB to 35LB range and is fine.

[another69]

It seems most SBC flywheels are in the 30# range. I was thinking a lightweight 15# steel, but I don't know enough to make an informed decision. I've weighed my car (3160), but I'm guessing on the power (425HP now, hopefully 475-500 after rollercam swap). I have 3.50 gears w/ 24.5" tires.

[JodysTransmissions]

To utilize a 15 pound aluminum flywheel of the street, your torque multiplication must be at least an 11 or higher. Your transmission 1st gear ratio of 2.87:1 and your differential of 3.50:1 will fall short. 2.87 x 3.50 = 10.045

[another69]

Does weight and tire size factor into that? Also, because I will be using a steel flywheel, I'm trying to avoid having a tire fryer that accelerates slowly to the shiftpoint. Do they make something in between? BTW- its an ext balance 406, (168 tooth)

[JodysTransmissions]

McLeod has a 25lb flywheel that might fit your needs better. I would suggest calling Red and discussing your vehicle stats with him.

[70camaro406]

BTW- its an ext balance 406, (168 tooth)

I also have an ext balanced 406, and I, too, plan to use an aluminum flywheel, probably a RAM with billet steel inserts - #2523, that weighs 18 lbs. I think you'll be fine with one of those too. Remember, 406's are pretty torquey and can afford to give up a little down low to allow for launches without all the tire smoke. I even plan on the TKO-600 with 3.42 gears and 27" tires. From what I've read and heard from many people, if you go too deep with the rear gear when using a TKO-600, it renders 1st gear almost useless. I know many people that can start out in 2nd gear even when using 3.73's. Now I'm not sure if they are using aluminum flywheels or not, but with a torquey engine, it shouldn't matter. I'm looking forward to the quicker revs, as I had a heavy 10" converter hanging off the flexplate, and even though it revved relatively quick, you could tell that it was a heavy converter.

[Twentyover]

To utilize a 15 pound aluminum flywheel of the street, your torque multiplication must be at least an 11 or higher. Your transmission 1st gear ratio of 2.87:1 and your differential of 3.50:1 will fall short. 2.87 x 3.50 = 10.045

Without trying to be a jerk (because I can be one so easily when I try), I'm not getting where you pull the 15 lb needs 11:1 first overall. It appears the basis for that statement is only your positive experience w/ those numbers, and you then execute a numbers manipulation to show another69 it's OK w/ his shorter tires because the overall distance travelled (not overall first gear ratio) is a little shorter than your overall distance w/ taller tires.

I guess I'm saying that I'm not sure you can make a statement like 15 lbs---> 11:1 first is OK. Is it OK in an MGB w/ a SBF * 205/50-14's? Is it OK on a Freightliner pulling 80K GVW and God knows how big the tires are? I'm thinking I'd like more of an explaination for the statement you made, since, to my way of thinking, it's a combination of 1st overall, tire diameter, car weight, engine displacement (and crank/reciprocating weight). Would the engine from a supertanker need more than a 15 lb flywheel if it was running an 8:1 first overall?

[JodysTransmissions]

Without trying to be a jerk (because I can be one so easily when I try), I'm not getting where you pull the 15 lb needs 11:1 first overall. It appears the basis for that statement is only your positive experience w/ those numbers, and you then execute a numbers manipulation to show another69 it's OK w/ his shorter tires because the overall distance travelled (not overall first gear ratio) is a little shorter than your overall distance w/ taller tires.

I guess I'm saying that I'm not sure you can make a statement like 15 lbs---> 11:1 first is OK. Is it OK in an MGB w/ a SBF * 205/50-14's? Is it OK on a Freightliner pulling 80K GVW and God knows how big the tires are? I'm thinking I'd like more of an explaination for the statement you made, since, to my way of thinking, it's a combination of 1st overall, tire diameter, car weight, engine displacement (and crank/reciprocating weight). Would the engine from a supertanker need more than a 15 lb flywheel if it was running an 8:1 first overall?

I gathered "another69" posted vehicle specs and ran his info off of my baseline. Most of "another69" vehicle's info is in this posting. If you re-read my posts, I could not fully bless his vehicle, there are too many variables. This is a forum and a great place to make people stop and think outside the box.

Yes, each vehicle is different and you are partially right but, I look at the 1st gear ratio, differential ratio, tire diameter, car weight, camshaft profile, heads, exhaust system & displacement.

Your MGB vehicle info is too vague to answer your question.

I never talked about a Freightliner pulling 80K! But, to answer your specific question, a 15 lb flywheel would never work with a Freightliner tractor! Do you know the weight of a Freightliner flywheel?

The bottom line: if you ever drive a vehicle that has been properly engineered for an aluminum flywheel, it is a blast. My Dad is using an aluminum flywheel on his 1953 Ford Flathead 5 speed car and he will never use a heavy flywheel, thanks to me.

Thanks for your questions, you made some good points. I hope I explained myself better.

[Steve1968LS2]

Engine, weight, gear, tire size are but a few of the important thngs to consider. Most times a billet flywheel will weight in the 30 LB to 35LB range and is fine.

lol.. my flywheel is 15.5 lbs..

Once you're moving a light flywheel is great as it lets the engine rev very quickly.

However, it's not as good at getting the car moving from a dead stop. If your gearing is wrong it can be a real PITA in stop and go traffic since the light wheel doesn't store as much energy due to it's lack of mass.

It took a bit to get used to how to work the clutch (felt different) but after a bit it's no big deal now.

[minendrews68]

The last Camaro I built I used the heaviest flywheel I could find. The reason being the car saw some track time and occasionally some (yes it's true) street racing. I found that the engine rpm's fell far less between shifts with the heavier flywheel than the lighter one I had in it at first.

[JodysTransmissions]

The last Camaro I built I used the heaviest flywheel I could find. The reason being the car saw some track time and occasionally some (yes it's true) street racing. I found that the engine rpm's fell far less between shifts with the heavier flywheel than the lighter one I had in it at first.

There was a time when I thought you needed the heaviest flywheel for drag racing too.

My partner drag races on the MANDRA circuit. I was replacing his transmission 1st gear at least 4 times a year in his Jerico 4 speed. He would also twist his Strange axles in his Dana 60 at the splines. The axle splines looked like a speedometer drive gear, thats how badly the splines were twisted from the hard launches.

His car is a 1962 Chevrolet Impala and weighs in at 4200 lbs with him in it. 409ci, , heavy flywheel, 4speed, 5.38:1, 9.70 1/4 mi, not bad for a tank!

About 8 years ago we changed out the flywheel for a 15 lb aluminum. Since then, I have never replaced any transmission gears and he never saw another twisted axle. No et was lost either with the aluminum flywheel. The car lost the violent "bang" on launch, but that was a good thing. The Jerico was sold a few years ago and still looked like new. A G-Force 5 speed is now on it's 4th season with all of its original gears. I know the longevity of the driveline is all due to an aluminum flywheel.

[another69]

Driveline abuse is something I didn't even think about, though I've heard that a lightweight flywheel will not dampen engine harmonics as well as a heavy one. I have not weighed my torque converter/ flexplate combo yet as a comparison. How light do you think I can go without having trouble leaving a stoplight? I'm waiting to call Mcleod and others after Christmas.
BTW- I'd be pretty proud if my motor could twist my Strange axles!

[JodysTransmissions]

Driveline abuse is something I didn't even think about, though I've heard that a lightweight flywheel will not dampen engine harmonics as well as a heavy one. I have not weighed my torque converter/ flexplate combo yet as a comparison. How light do you think I can go without having trouble leaving a stoplight? I'm waiting to call Mcleod and others after Christmas.
BTW- I'd be pretty proud if my motor could twist my Strange axles!

You must use a Fluid type damper with an aluminum flywheel.

This is my street friendly Chevelle stats using an aluminum flywheel:
Trans 1st Gear: 3.27:1
Differential Ratio: 3.42:1
Tire Diameter: 27.99"
Torque Multiplication: 3.27 x 3.42 = 11.1834

Your vehicle stats:
Trans 1st Gear: 2.87:1
Differential Ratio: 3.50:1
Tire Diameter: 24.50"
Torque Multiplication: 2.87 x 3.50 = 10.045
Your smaller diameter tires will net you a lower 1st gear feel. This difference can be multiplied to your torque multiplication.
27.99/24.5= 1.1424

Your effective Torque Multiplication: 10.045 x 1.1424 = 11.4754

Your numbers seem like a good candidate for an alumimun flywheel but, I cannot be 100% for sure with your engine stats. Call some of the more known flywheel tech lines and pick their brain.

I have compared a steel vs aluminum flywheel with my 502 and I will always use an aluminum flywheel with any future build. My 502 revs up like a can-am engine and sounds nastier than it actually is with the aluminum flywheel. An added plus is that I can slow down to 35-40 mph in 6th gear and roll back up to speed without downshifting. This is all due to an aluminum flywheel, the standard weight flywheel could not do this.

The only negative I have is that my 2nd gear ratio in my 6 speed is 2.22:1 and the take-offs in 2nd gear are not user friendly with a 3.42:1 differential.

[another69]

Thanks for the above and beyond reply!
I really like to drop weight wherever I can, so I hope a light flywheel will work out. I guess I'll get some input from a few more manufacturers before I buy. I have a new, but stock type rubber isolated damper- not even SFI- so an upgrade to a fluid damper should probably be done either way. I never knew it was required with an AL flywheel, though. I don't know what type of clutch you're running- I'll probably use an organic or kevlar- but do the AL flywheels affect chatter at all?

[opnwide]

I put one in my "97 Viper. They said I would have to slip the clutch more on takeoff, but with 488ci, I didn't really even notice. Launches are a little easier too, as I don't smoke the heck out of my Pilots. I plan on running an aluminum behind my 455 Poncho also. I do not expect a problem with drivability.

The idle on the Viper is a little more "lumpy". Is that so bad?

[parsonsj]

I'm going on my third clutch in my car:

1. I started with an ultra-cool dual disk 8.5" custom setup that weighed less than 25 lbs complete with flywheel. I didn't like it, and it burned up pretty quickly from slipping it to get the car moving.

2. After that I went to an ordinary LS6 clutch (56 lbs. with flywheel). I liked it a lot, though high rpm shifts were difficult. I burned it up after a couple of years. I did get it from the garbage can at Norris Motorsports, so it was a bit "used" to start.

3. Now I'm going to try an RPS Street Twin. It weighs 40 lbs. with flywheel, so I'm hoping it will be "just right". I'll report back when I get it installed.

And if anybody wants a used Fidenza aluminum flywheel (LS1), let me know.

jp