Lightweight flywheel options and selection criteria.

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gzig5

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I've dropped the 340 block with the builder and we are going with a much lighter piston/rod combo on the stock stroke crank than the L2613 pistons I had originally planned for. It should rev quickly and run smoothly. The used OEM flywheel I picked up for the four speed conversion is usable but has some heat stress cracks. He's suggested going with a lighter flywheel and now I'm a bit unsure on which option to go with for my application. Stock units are about 30lbs, plus or minus. The light weight steel units come in around 20-22lbs. The LW aluminum units are 12-14lbs. So far I've got a Mcleod 10.5" Super Pro Street clutch kit and A833 and 3.55 gears behind it. Engine will be a 340 with heads and cam to support 450-475hp in a ~3700lb E-body. I will have a lot of street driving with autocross and road course track days as much as possible. Might hit the drag strip from time to time but that is not the focus of the build. 3.91/4.10 gear and Gear Vendor or TKX may come down the road after I've got some mile on it.

Now the OEM made them that weight for a reason and racers make them lighter for other reasons. Usually a compromise with one or the other not doing everything well. Looking for suggestions on general weight class to go with and specific model recommendations or ones to stay away from. I'm leaning towards the middle ground 20lb class steel ones. Ram has one that is about $300 new and I would think should do what I'm looking for. Does that sound about right or should I be looking harder at the aluminum ones? My thought is that the 12lb unit with less inertia, would not be as competent on the street in the off idle area.
 
Wayyyyyyyyy back I had a 340 in a early dart and I used the 10 inch (9 1/4) flywheel to lighten the load and it was just about too light but it worked well with a 4.10 and a 3.09 first gear. I think you should use a std. flywheel with your combo.
 
RustyRatRod said:
I don't like aluminum for any application.
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Me neither! There's an aluminum Centerforce just sitting in my shed that has half a summer on it. What I hated most was the "lurchiness" at slow speeds. Not to mention, I could never get a consistent launch with the damn thing.
 
Dan Brewer said:
I wouldn't use an aluminum wheel on the street.
If you want light weight steel: FLYWHEEL 10.5" 6-BOLT V8-RAM-LIGHTWEIGHT 130 T - Mopar A833 4-Speed Transmission & Component Specialists
Flywheels store energy. Lighter wheels will allow the engine RPM to pull down easier when you start to engage the clutch.
Have a read here also, direct from the Ram website: CLUTCH UNIVERSITY – CHAPTER 4 - RAM Clutches
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Good stuff. That's the one I was thinking of. I want it to rev best it can but I don't want it to be difficult to drive around town, which I intend to do regularly when the weather allows. Some good evening reading for me. Thank you.
 
For your application I would use the 20 lb steel.
I did run a 12 lb aluminum wheel behind a 370hp LT1 in my 57 chevy, and I LOVED it! It revved so quick it was amazing, and I was still running the plastic 8.2 dropout rear end, so I did NOT need the heavy flywheel transferring a lot of torque. And the 4.56 gear helped too. A scattershield was ABSOLUTELY MANDATORY.
The light flywheel helps with acceleration as well, especially in the lower gears. Much more so than even lightweight engine internals.
Imo, a heavy wheel is only necessary for a car with almost no gear (2.76/2.91, etc)
Edit: whatever you get, get an SFI approved version. (Have you ever seen a flywheel/clutch explosion? I have. UGLY!)
Edit2: I heartily endorse a scattershield too. Most racing sanctioning bodies require one, or should.
 
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The lighter your flywheel the deeper the rear gear you'll need to run, or it'll fall flat on it's face when you try to launch. If you need to run a semi street-friendly gear, you can get by with a middle ground flywheel. Highway gears, heavy flywheel.
Stay away from aluminum flywheels that don't have a ferrous friction surface (not sure if they even make those anymore, maybe I'm dating myself...)
And definitely yes to a scattershield (with block plate) if you intend to turn some RPMs with this thing. But if you weren't intending to do that, you wouldn't be building it this way and we wouldn't be having this conversation.
 
Aluminum flywheel= road racing/autocross
Lightweight steel= drag racing
Heavy steel (stock) = street car

My experience.
 
Newbomb Turk said:
With your gearing and power there is no way I’d run a steel flywheel.

It’s not 1975 any more.
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I think it’s more application dependent than anything else. With his gearing and hp in a street car I absolutely would run a steel flywheel. If his engine was in a Miata road racing I’d wouldn’t run anything but a super light aluminum.
 
i ran a lightweight aluminum wheel from 10,000 rpm behind my 318 in the 64 and 65 darts. commando box (3.09 1st) and 3.55's out back.

absolutely wonderful on the road course and auto-x. a real chore to drive on the street. with a race style on/off clutch it was nearly undriveable in traffic.

i'd steer away from a full aluminum wheel and go with a lighter than stock steel unit for your application.
 
Thanks for the feedback, this is really what I was hoping to get. Real street experience with the options. While the track performance of a flyweight flywheel is very desirable, reasonable street driving manners are higher priority. I am planning on driving the car nearly every day in the warmer months and I don't want to be taming a bucking bronco. As I suspected, the lighter you go the less fluid it would be for tame street driving. I try not to drive like a 19yr old BMW owner most days around home. :p As with everything in life, there are compromises and for me I'm going to lean to the street side at this point in the car's life. I've got time to ponder the question but hope to have the car back together (it's currently stripped and missing roof, quarters, and tail panel) and running by this fall. I will give the 22lb one a try, but probably wait until I go to a 3.91 or 4.10 rear gear. Car was an automatic so I'm setting up the four speed from scratch and want to have as much forgiveness in the system as possible while debugging engine/trans/clutch, so starting with the OEM 30 pounder might be the better course of action. I'm not afraid to go back in and change things. I have a loose schedule of upgrades and fuel systems to try in coming years. But need to get it moving under power first.
 
I run a Mcleod 22lb sfi behind the 408 in my Swinger . W2 heads 246/250 on 108 cam and 3.91 gears. No issues street driving . A 3.09 first gear would make it perfect !
 
Like @mbaird, I too ran a 22lb McLeod lightweight steel in my W2 408 Swinger. When I had my 3.09 box in my car, it was great with 3.55 gears. With 3.23, it wasn't the best, but I now blame a lot of that on the McLeod RXT clutch, which has no modulation whatsoever, either on or off. At that time, I went back to a 30lb wheel, which definitely caused the engine to spin up slower.

Currently, I am finishing the installation of an aluminum 14lb wheel from RAM Clutches and 4.10 geared Dana 60, with aluminum driveshaft and Gear Vendors. All of this will be coupled to a McLeod borg beck and long pressure plate and organic disc. After searching around the net for info on aluminum flywheels, I came across Jody Haag, of Jody's transmissions. His advice when contemplating an aluminum wheel on the street is the necessity of 11:1 ratio in first gear. He claims this is a minimum, less than this and it likely won't be happy. I also spoke with FABO member @perfacar, who also agreed aluminum was the way to go for me.
 
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cpearce said:
Like @mbaird, I too ran a 22lb McLeod lightweight steel in my W2 408 Swinger. When I had my 3.09 box in my car, it was great with 3.55 gears. With 3.23, it wasn't the best, but I now blame a lot of that on the McLeod RXT clutch, which has no modulation whatsoever, either on or off. At that time, I went back to a 30lb wheel, which definitely caused the engine to spin up slower.

Currently, I am finishing the installation of an aluminum 14lb wheel from RAM Clutches and 4.10 geared Dana 60, with aluminum driveshaft and Gear Vendors. All of this will be coupled to a McLeod borg beck and long pressure plate and organic disc. After searching around the net for info on aluminum flywheels, I came across Jody Haag, of Jody's transmissions. His advice when contemplating an aluminum wheel on the street is the necessity of 11:1 ratio in first gear. He claims this is a minimum, less than this and it likely won't be happy. I also spoke with FABO member @perfacar, who also agreed aluminum was the way to go for me.
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I "think" that my A833 trans has a 2.66 first gear but I need to get the book out and verify that before I make a move. That would put me at (2.66 x 3.55) 9.4:1 currently If I'm reading you right, which is considerably short of the 11:1 for aluminum. Even more reason to stay with one of the steel ones. I also have an A833OD trans on hand and I thought those had a steeper first gear. I acquired it with the thought that it would be a cheap alternative to a Gear Vendor or TKX to get an OD for longer road trips and around town driving. I had a 77 Aspen RT forty years ago with the 318/A833OD combo and it seemed to drive pretty well even though it was a pooch.
 
Well, I am 100% sure that I would NOT run a lightweigt flywheel in your combo.
If yur gonna run that combo on the street, Yur gonna find out a few things real quick;
1) those 3.55s are gonna suck, and
2) you'll be begging for a big fat heavy flywheel, and
3) you just cannot idle it down slow enough in First gear, to not have to be slipping the clutch all the time.
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With a regular A833/3.55s each 100rpm is .85mph, so 850 rpm is gonna be ~7.22mph, and every powerstroke is gonna telegraph straight into the chassis, and straight up the steering column.
Parading is absolutely never gonna happen with that combo.
Therefore;
I recommend the heaviest doggone flywheel you can find, and a Commando 3.09 low, and then the 3.55s might be bearable; this will get you 850rpm @6.2 mph, but still not parading. To get to 4 mph@850, will take a 5.5x gear
To get to 450hp with an iron-headed 340 means a cam of about 292 or more duration, right? Yeah I ran 4.88s with that, lol, for a starter gear of 266x4.88=12.08 and to get to 4mph, the idle was cranked down to 650, any slower and the 292 cam began bucking, even with a factory heavy flywheel. I eventually got that cam down to 550, but that was a chore! and how long do you want to parade down low like that?
So, with a cam like that, (mine was 248/249 @050), and a manual trans, in all honesty, parading was out. I pulled the cam.
IMO
450 hp on the street with a 4speed; been there/done that/never going back. and my car is/was ~3650 with me in it. and,
BTW, 3.55s is my gear of choice because 1.92Second gear takes me from 3000@35mph, to 6000@70mph, almost perfect for a nearly 100% street-driven car.
Obviously, your application is slightly different, lol.

But, yakno; you can change a flywheel out in about an hour, lol; and not much longer to swap out the rear. So, we, or maybe just me, are making much ado about nothing.
 
gzig5 said:
I acquired it with the thought that it would be a cheap alternative to a Gear Vendor or TKX to get an OD for longer road trips and around town driving.
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For a 450hp 340, bad idea man . The gears are too far apart and your 340 will fall off the cam every stinking time. I had the same idea, and it took a GVod, run as a splitter, to keep the engine in it's operation range.
That worked really well but HAVING to split every gear all the time, on the street, got old.
If you do this with the GV, I highly recommend to take the factory od gear out, and ship it to me before you blow it up. ..... cuz I got two od boxes here in the which that gear is mysteriously missing lol. (I blew it up) With the GVod you wont be needing it anyway, and if you do blow it up, I found out, that it can take the rest of the trans out with it.
but I gotta tell ya, that box, by itself, was horrible with my 367 cubes and a 230* cam, never mind what it might be with 25 less cubes and a cam 3 sizes bigger. Sell it, friend, just sell it.
For your application, I think I would like a Commando. The 3.09 is not as far away as it is in the od box, and the rest of the gears are just like the 2.66 box. So if you gear right for your track, that 3.09 might be just the thing to get you launched. I run it on the Street with 3.55s and about 430 hp now, and I really like it. But, to be accurate, I'm running OOTB alloy heads, and cylinder pressures over 185psi. and I'm running those KB107 pistons that IIRC are 502 grams? So, I'm real happy with the factory flywheel. For me, First gear is now a dump-it and go deal, and I can get her down to 3.5mph, which she will idle along at, all by herself, for as long as needs be.
but forget that od box; she's just for a lo-perf engine with a super-broad flat torque curve, like say one running a 114 Lsa, lol.
 
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gzig5 said:
I "think" that my A833 trans has a 2.66 first gear but I need to get the book out and verify that before I make a move. That would put me at (2.66 x 3.55) 9.4:1 currently If I'm reading you right, which is considerably short of the 11:1 for aluminum. Even more reason to stay with one of the steel ones. I also have an A833OD trans on hand and I thought those had a steeper first gear. I acquired it with the thought that it would be a cheap alternative to a Gear Vendor or TKX to get an OD for longer road trips and around town driving. I had a 77 Aspen RT forty years ago with the 318/A833OD combo and it seemed to drive pretty well even though it was a pooch.
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Yes, at 9.4:1 I'd consider the light weight steel for sure. Knowing what I know now, I wouldn't buy a 30lb again.

You are correct, 1st gear in an OD is 3.09, same as the old Commando boxes. When I had that trans and 3.55's, the light steel was absolutely awesome.
 
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