Heavy or lightweight flywheel?

[Lil Demon]

What weight is recommended for a 71 Demon, 340 setup. Street use with the occasional trip down the 1/4 mile. I currently use a Ram 28# flywheel but only after a few hundred miles the ring gear came loose. I tried calling them but they're all about emails now and I've been waiting with no response. I decided to put a few welds on it and it's working fine but I'll be driving it easy until I get a new flywheel. I noticed Ram and Mcleod offered lightweight 22# flywheels with a footnote of using heavy flywheels for track use and or heavy car. I know the Demon is a light car. It's a healthy 340 that likes to rev to about 7k. What flywheel should I use?

 

[33IMP]

I would use the lightest flywheel i could find.
I replaced a 35lb cast iron wheel with a 13lb aluminum wheel, many years ago, in a 57 chevy with a 360hp 350.
I LOVED it! (I did have a scattershield, and 4.11 gears)
The motor revved instantly, pulled harder in gear, and with enough gear, didnt miss the smoothing effect of the heavy flywheel at all.
Heavy flywheels are used in heavy cars and some racing cars for the inertial effect, to leave an intersection, or a starting line. After the car is moving, extra flywheel weight just makes the car accelerate slower, as it acts as if the car is heavier. Visualize trying to spin a bowling ball tied to a string, verses a golf ball and a string. Which is easier to spin? Heavy wheels are used in small displacement high revving drag cars with great traction, where the car would stumble without the inertia. Vw drag cars are typical. Without a heavy flywheel, they wheelie, then fall on their face.

 

[valiantpatrol]

I could not agree more with 33IMP's words of advice. Like him I loved my aluminum flywheel on the street but ran a narrower tire than I might have otherwise so they would spin a bit and NOT hook. But at the track my 2.5L SL6 just nosed over and stumbled with the slicks on it and that aluminum flywheel. So you can't have optimum performance in both worlds and thus your choice. Similar to the difference between a car that is quick (0-100 in little time) and one that is fast (goes 190 mph but takes a couple miles to get there). I will ad that the difference between 22# and 28# Flywheel may not even be noticeable. the difference between 28# and 13# definitely is !

 

[Lil Demon]

I figure it’ll just rev a bit quicker. Car is light, engine is lively and tires hook hard with the 28#’er. I’ll report back what it does with the 22#’er thanks for the great advice

 

[AJ/FormS]

For a streeter
it really depends on your starter gear, and your engine's torque down low.
With say the regular 2.66 low A833 and 3.23s your starter is 8.59. With a low-torque engine, taking off with just 8.59 takes a bit clutch work. So a light flywheel will lose rpm and be a lil herky-jerky.

With same trans and 4.10s, your starter is now 10.91, or 28% better, and taking off is less of a chore. So now you can use that lightweight FW.

Butum, I have a hi-torque 360 with a 3.09 low Commando trans and 3.55s for a starter of 10.97, and I have a factory-stock heavy FW.
What I do is, with the trans in first, but not yet engaged, I blip the throttle just a lil, then more or less dump the clutch, letting the heavy FW dump it's energy into "launching" the car.
The heavy FW also smooths the lumpy idle.
And it allows the engine to pull the car along at 550 rpm on flat,level,hard ground, at 4 mph, which for me is must-have. It will pull down to 500rpm/3.6mph, if I need it to.
Try that with a lightweight FW.

 

[Lil Demon]

Very interesting info I did not realize. I imagine it’s healthy torque wise. Trans is a ViperT56 with 2.97 1st, 4.10’s out back and I can cruise along shifting at 1300 rpm and cruise in 6th gear just above idle with no jerking. I can take off on a slight grade from a dead stop in 4th. What you mentioned about it settling down a rough idle definitely has my attention. My engine has a fairly radical idle and I have to keep the idle at 1k to avoid my headers banging the steering arms and or torsion bars. Even with the TTI headers you guys it’s a tight fit. If I go lighter I’m concerned it’ll become even rougher. Now I’m really puzzled on which to get. Very disappointed with my Ram flywheel just letting the rings gear loose like that so quickly. I don’t feel good with the welds on it I’ve been told it isn’t a good idea especially on a motor that likes to wind up. What’s you all opinion on that? We put 6 good tig welds on it but not comfortable

 

[AJ/FormS]

With a starter gear of 12.18 taking off should not be a problem.
In your case, at 1000 rpm your minimum roadspeed is around 6.5 mph, so again, you don't need a heavy FW.
So all-in-all, with the new information I see no reason to run a heavy FW.
Butum, I still would.

I have never seen a ring gear come loose period, unless it cracks. When the RG is installed, it is first heated very hot to expand it, then quickly dropped onto the FW which was earlier set up to accept it, in such a manner that when it drops on, it is in it's final resting place. As it cools it shrinks on. I can't recall ever seeing a Mopar FW with a welded-on RG.
After installation, there is nothing you can do to the FW that would make it fall off, unless it cracked.
So, IMO, if a RG comes loose, that is defective. Either the RG was sized wrong or it has cracked.
-----------------------

But I'm curious why your engine needs to idle at 1000. Just how big a cam are you running, and at what Dcr or cylinder pressure and what idle-timing.
The biggest cam I have tuned is the 292/292/108; and while there is no denying that it has a personality, I have got them fairly stable at 750.
But yeah, I had to adjust my TTIs to not rattle on things.

 

[Lil Demon]

I’m actually waiting on my low speed air bleeds cause I agree it shouldn’t need 1k rpm to idle smoother. I’m hoping I can make it happier after some fine tuning in the idle circuit. Meanwhile I took a really good look at the ring gear but didn’t magnaflux it. It may have just been sized incorrectly. I’m just hesitant to go back with the same flywheel don’t really feel like giving them more of my business. I guess I’ll get the McLeod 22#er. I’ll let you guys know how it goes. Thanks for the input. Much appreciated

 

[mopardude318]

@AJ/FormS do you have a video of your car at idle, I’m really curious of the 550 idle.

 

[Lil Demon]

FWIW my car is a 246/252 on a 106

 

[yellow rose]

FWIW my car is a 246/252 on a 106

If you are going to buy a lighter flywheel, buy an aluminum flywheel. Dropping a few pounds isn’t anything.

You have PLENTY of first gear. All that flywheel weight is doing is beating up parts. There is no reason to run anything other than an aluminum flywheel unless you have 200 HP in a 4000 pound car with a 2.79 gear. Everything else gets aluminum.

 

[AJ/FormS]

FWIW my car is a 246/252 on a 106

Yeah that is very similar to the 292/292/108 Mopar; if perhaps a lil smaller.
I've had no trouble getting that down to 800, and with a lil finessing 750, even 700 with conservative timing. You just gotta get the transfer slot set right, and all the air entering the engine has to have fuel in it. So if you're cracking the secondaries for Idle-Air bypass, you better have a 4-corner idle carb. Or some method of getting that secondary air entrained with fuel.The right amount of fuel.

 

[AJ/FormS]

@AJ/FormS do you have a video of your car at idle, I’m really curious of the 550 idle.

I wish
My cam is an old Hughes (2004); 276/286/110, 230/[email protected], 549/[email protected] arms
she runs an ancient 750DP on an AirGap
To run that slow, I dial back the IdleTiming electronically to ~5*. leaving the Transfer slot sync alone. Normal idle is 700@14*. The heavy flywheel keeps the tic-over stable; just like it does on an old JohnDeere.

 

[DrCharles]

I'm staying with my 30 lb steel one for now... 2.66 1st, 3.91 gears.
My 316 advertised/107 cam ([email protected], .652 lift) needs all the off-idle help it can get, even in a 451. Best stable idle is at 1200 but I can get away with 1100. Retard the timing and it just noses over and dies. So no parades for me ;)

 

[AJ/FormS]

I'm staying with my 30 lb steel one for now... 2.66 1st, 3.91 gears.
My 316 advertised/107 cam ([email protected], .652 lift) needs all the off-idle help it can get, even in a 451. Best stable idle is at 1200 but I can get away with 1100. Retard the timing and it just noses over and dies. So no parades for me ;)

I haven't tuned anything that Big; not in cam size nor cubes nor power, so anything I mighta said in the past, generally, you can ignore,; unless I said it to you specifically,lol..

When I had the 292/292/108 installed, that 367 of mine had a bit of an idle-lope.
But with the current 276/286/110, I can't hear it, nor feel it, until the rpm is way down; Ima thinking the factory FW is smoothing it right out.
What I find is that (not yours) that if the Transfers to mixtures is off, that yes there is a sharp drop off related to retarding the timing. But the closer the sync is, the slower it will run by retarding the timing.
The only reason I don't retard mine to less than 5*BTDC, is that's all I got left in my electronic dial back,which is normally set to 14*. The box has a range of 15*. I allocated 9 to retard and 6 to advance. I use the 6 advance during the warm-up period, so it idles on 20*. And I use up to 9* retard for parading, which is then still 5* advanced.
But I know that my 367 will idle on less than 5* if I wanted it too, because at 5* it still has enough power to pull itself, on a flat, level, hard surface. BTW; Your starter-gear with 2.66 x3.91=10.40 is about the same as mine (10.97). That is a sweet street starter-gear.
IDK anything about to how to tune your combo, but if I was allowed just one guess, I'd guess she might have a low-speed fueling issue, directly related to ......... to your piston being about half way up the cylinder on the intake stroke, before the valve finally closes, lol.

 

[KrisKringle]

Hello all from Germany. If you know me on FB, than you know that I am putting the original motor together for Lucille. 340, +0.40" with a Molnar 360 stroke crank, Molnar rods and Icon 360 +0,80" oversize pistons with Total seal rings. I will be running a mechanical roller Lunati camshaft, Trick-flow heads as well as the Proform 4 bolt mains. Of course the six-pack with hidden NOx.
The motor that is in the car now has a lightened Schieffer flywheel. It appears that they are no longer in business. I am looking for recommendations for a flywheel and clutch combination. Back in the "Front Street runner days" I needed a clutch ever 5.000 miles...
When all of the parts finally arrive, I will fly over to the States to put the engine together. Other than myself, there are only two other folks that I trust to put this engine together except for myself. One is my Pop (86 years old) and a guy at the MoParShop here in Germany. I do not build "Velcro" motors.
The motor is going back in a '68 Barracuda with 3.55 rear ratio and if you did not understand the question, a 4-speed. Not an OD box either.