what flywheel

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Weedburner that is some very nice data

1st gear 2000 to 4000 rpm- engine #1 1634 rpm/sec........engine #2 1910 rpm/sec (276 rpm/sec difference)
1st gear 4000 to 6000 rpm- engine #1 1975 rpm/sec........engine #2 2217 rpm/sec (242 rpm/sec difference)
Click to expand...

So let me see if I understand this right;
If you recalculate the difference in rates to get an average,would that be (276 +242)2 = 259 average from 2000 to 6000? So say I have a streeter that hits 60 mph at 6000, at the top of first gear; and it takes 5 seconds, with the heavy flywheel. Are you saying that the lighter fw will get me there 259/6000 x 5=.21 seconds faster?
As I recall this was from a dead hook?

OK I can see this as useful on the track.
But how useful is this to me,a streeter, who will spend the first 4.999 seconds spinning?
What do I have to spend to make my streeter hook, by 2000rpm?

You see where I'm going with this right?
 
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mbaird said:
So that means less rotational mass ? Because the counterweight offsets the rods ?
Click to expand...

Yes. The 2nd engine's crankshaft had much lighter pendulum cut counterweights, drilled rod throws, and scalloped flywheel flange to begin with, but the lighter aluminum rods and flattops made it possible to further reduce counterweight dia.
 
I can't break down the math and physics of it but I can tell you from real world experience that if I have a light flywheel
on my birt bike it will in fact rev faster and be "quicker" which is an advantage on a MX track. But it is a distinct disadvantage
on a technical singletrack trail with a 3000' climb in elevation over obstacles and using varied rpms constantly (lugging).

If I was strictly Drag Racing I would go light.....but for street a bit heavier for the very reasons A/J pointed out.
 
mbaird said:
Im interested in this subject as I am starting a 408 4sp project and need a flywheel... I am also considering a 3.09 1st as well and would like tto hear pro's and cons. I have my own theories but would like some practical input.
Maybe a new thread ?
Click to expand...

My 367 was a little soft with 2.66 x 3.55=9.44 starter gear and the 292/508/108 cam, even at 11.3 Scr. It took 4.30s to get over that. 2.66 x 4.30=11.44
My 367 was not soft at all with 2.66 x 3.55=9.44 with a 270/276/110 cam at 10.9 Scr (gasket swap)
My 367 was only a little soft with the 9.44 starter gear,with a 276/286/110 cam and still 10.9Scr. The 3.09 x 3.55 =10.97 starter gear cured it.
Keep in mind that this is a streeter and all of these iterations roasted 295/50-15s to past 60mph under WOT. So the softness was only noticeable when motoring away from a dead stop using very small throttle openings, as in normal take-off.

Here's the real reason I have a 3.09 low; with my gearing,30 mph =2540 in second gear.......................and 4088rpm in first......... So....cruising along in second at 2540, I don't have the torque you might have, but a quick downshift and I got power! With a 2.66 that would only be 3400ish rpm. Or I would need 4.10s to equal that 4088. And....... we all know how much fun cruising the hiway is with 4.10s!
Sometimes I put it into second-od and cruise at a tic under 2000, and sneak up on somebody. Then I outshift o/d and simultaneously downshift, and nail it. You guessed it, nobody is sleeping anymore!
So, yeah the 3.09 helps me get motoring from a stop,and the 3.09 low makes up for not having an overdrive,but more importantly,it helps set the stage for stroker-type acceleration from 30 mph to 60
Remember I am geared for 47mph=6400.At which time I hit the GearVendor and it carries me to 60@6400. The rpm drop at the shift is 1400 rpm (to 5000). The engine is quite happy to pull this gear to 7000@66mph. That is the real reason for me to have the 3.09low.
With stroker torque, I can't see you needing a 3.09 low.
FWIW
Whatever you do, forget about the 3.09 O/D box.I tried every A833 tranny out there,and at one time,I had every chunk from 2.76 to 5.13 except 4.56s,and 3.73s;And I have a GearVendor. I can tell you this one thing; that od box is not suitable for a high-reving 367 streeter.And the less torquey it is the worse it gets. If you gear it up until 2nd is just right, then first becomes a granny-gear, and third is still way out there. Plus the o/d gears snap like dry-toast, sending shrapnel all through the box. Now, your stroker may pull it just fine with a small cam, cuz strokers with small cams make awesome torque at low rpm. But the first time you put it into O/D, and are not careful, chances are very good that you will shatter that little o/d gear, or shred all the teeth right off it. That gear is strictly for putting along.
 
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I am not using an O.D. I am picking up a 66 833 this weekend that should have the 3.09 and I have another 833 with std gearset.
I am trying to build a "Suoer Sleeper" 69 340 Swinger... the only visual giveaway will be TTI step headers.
I am thinking of running 3.23s on the street and the 3.09 1st would work well..... just not sure how that would effect track performance if I toss a set of 3.91s in .
Will the torque mask the big ratio jump ?
 
mbaird said:
I am not using an O.D. . Greeeeat I am picking up a 66 833 this weekend that should have the 3.09 and I have another 833 with std gearset
I am trying to build a "Suoer Sleeper" 69 340 Swinger... the only visual giveaway will be TTI step headers.cool
I am thinking of running 3.23s on the street and the 3.09 1st would work well It will..... just not sure how that would effect track performance if I toss a set of 3.91s in . Probably too low, more like 4.30s depending on the power-curve.
Will the torque mask the big ratio jump ? yes
Click to expand...

The 3.09 to 1.92 is a very nice split, I really really like it.This is a 1.92/3.09=62% split, meaning at the track,if you shift at 6400, the Rs will drop to 62% or 3977. Around town it is also excellent. Pulling the stick at 2800, my Rs drop to 1736, and I have plenty enough torque there to motor away in traffic, on account of second has an overall ratio of 1.92 x 3.55 =6.82. This number is magical for my combo.It is the exact right ratio for cruising second gear in traffic ;30mph is 2540rpm. My 367 has plenty of torque there for just tooling around.
With 3.23s second overall would be 6.20. This will make 30mph be 2311 rpm, with 27"tires soooooo, depending on your torque curve,it can make or break your city cruising pleasure.This is also why I don't use 3.23s; it would break my cruising pleasure.
I know my combo would be fine with 3.23s, I just don't need them, on account of the GV, and 2311@ 30mph is too low, for me.

There is one other thing you should know; for fuel economy, your hiway rpm should be slightly higher than whatever rpm it takes to cause your engine to vacuum peak, when free-revving. The vacuum peak indicates the first rpm at which the engine is becoming efficient. 3.23s and 27s rev 2600 at 65mph, and I'm betting this is well above your vacuum peak.So no problemo. But if your engine peaks at 2200,say, then 55mph would be the lower end of the preferred cruise rpm.
Im guessing at numbers for illustrative purposes only.
All numbers are with 27 inch tires.
 
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It's just a 408 with W2's ( on there way to the porter) and M1 dual plane and solid roller cam yet to be speced
 
Since the 3.09 is on the way stick it in there, and here's why; From the looks of your combo upcoming, it appears that you are building a bit of a screamer.If you run much more than say a 240@050, then the 3.09 may be welcome.
In the lightweight Swinger, that is gonna be a lot of engine..
I'm on the edge of changing my mind, and heres why; with 3.23s; the 3.09 will run the engine up,to 7440 at 60 mph, whereas the 2.66 will only run it up to 6400. You see where this is going, right? If you have to shift, the 3.09s will hurt you.
Whereas a 2.66 x 3.55 will get you 60 mph@7000. So again, the overall gearing will be very much tied to the power-curve. But if you can't make it hook, it matters not a hoot. I wanna say you are building too much engine for the street, but that sounds whacko,eh? Or at least too much for the manual trans.
Now a 727 with its 2.45low and your 3.23s and a 6400 shift rpm will work very nicely. But you are gonna need some TC to get moving. This combo hits 62@6400 with 5% slip. The starter gear is only 7.91 plus whatever the TC kicks in, say 10% then 8.70. This is gonna need some rpm to pop off the line.
All numbers are with 27 inch tires.
So the upshot of this now, again depends on the power curve, and what exactly you are trying to achieve.

I built my combo many times over, before it was just right. The power curve really needs to be married to the gear ratios for everything to come together. After; 3 cams, 3 intakes, 3 carbs, 4 trannys, 5 rears, and the GV, I think I finally got it, and I think the 93 mph in the 1/8 is icing on the cake.

Yeah, maybe hold off a little til the engine's power curve is known.

BTW, lest you think I'm rich, everything between "cams" and "GV" was collected over a lifetime, since the mid 70s.
 
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On the street I will just be puttering around with an occasional "badboy" display when nobody is looking.
I like the idea of the 3.09 1st because it will allow me to creep along on a back street or parking lot and launch
like a madman on the strip using 3.91s and 28x10" slicks with good old school super stock springs set up properly.

I still need to have a cam designed that will give me lift (.570-.600 wih 1.6 ratio) and duration (245-255ish ?) yet not sound too wild on the street ( maybe 110 CLA?)...

Back to the original post subject.... I dont want a jumpy or stalling car driving in town so I think I will stick to a stock flywheel. I'm glad I followed this thread.
 
You got a blow-proof bell? I think you will want a certified Flywheel.
And you won't be idling that beast around with 3.23s unh-unh,no!
Ima seeing a 950 rpm idle minimum, and that is 8mph. You will be slipping the clutch, probably at 10 to 12 mph already. Yeah IMO,that is too much engine for a manual trans on the street,IMO. You may as well put the 4.30s in right away,lol. This will bring your idle-roadspeed down to 6 mph. And you will still be slipping the clutch. Not because you don't have enough torque, but because the power pulses are hammering the flywheel, and the flywheel is sending it straight into those SS springs, which are sending them straight into the chassis, and up your spine and rattling your fillings out.LOL. Meanwhile your right foot will be playing footsie with the accelerator pump, and the cycle escalates until you clutch it and start over. Of course I am exaggerating a bit; I've never had a stroker, or an engine anything like yours. I'm just remembering my little 367 with the Mopar292/508/108 and the 9.44 startergear, lol.
I suppose you could fill the trunk with cement to act as a damper,lol
 
I had a 73 340 4sp Dart with w2's and a .638 roller /280ish comp so I know what you are referring to. And it wasn't too awefull. My 70 Charger had a 550 solid roller in a 440-6 and it was amazingly docile. But it was a 727 auto...

I am hoping that between the stroker and less duration a lot of the pulsing will be mitigated.
That car had an O.D 833 in it with 4.10s ( a member in Toronto owns it now)
 
AJ/FormS said:
So let me see if I understand this right;
If you recalculate the difference in rates to get an average,would that be (276 +242)2 = 259 average from 2000 to 6000? So say I have a streeter that hits 60 mph at 6000, at the top of first gear; and it takes 5 seconds, with the heavy flywheel. Are you saying that the lighter fw will get me there 259/6000 x 5=.21 seconds faster?
As I recall this was from a dead hook?

OK I can see this as useful on the track.
But how useful is this to me,a streeter, who will spend the first 4.999 seconds spinning?
What do I have to spend to make my streeter hook, by 2000rpm?

You see where I'm going with this right?
Click to expand...

These were rolling starts. With engine 2, the car gained 4000rpm in 1st gear from a 2000rpm rolling start in about 2.025 sec, engine 1 took around 2.226 seconds to do the same thing. Regular asphalt road on 28" tall street legal 275/60-15 M/T ET Street Radials and 3.73's (10.37 overall ratio in 1st). DSRPM climbed at a steady rate with no indication of wheelspin, regular everyday driving probably includes a lot of rolling pulls like these from down around 2000.
 
The OP and mbaird both need aluminum flywheels.



Lots of neat math but the trick is to not beat the **** out of the tire and the car.

Neither of you NEED all that FW weight.


And since it was brought up...don't take the entire weight of the clutch assembly to figure percentage of change with FW weight UNLESS you are changing the weight of the other components.

A 15 pound FW has 50 percent less weight that a 30 pound wheel. If all you change is the FW that's how you figure percentage of change.


Go aluminum and forget it.
 
So are you saying an aluminum clutch will make the car more or less easy to drive on the street ? Which will be 98% of its use.
 
yellow rose said:
And since it was brought up...don't take the entire weight of the clutch assembly to figure percentage of change with FW weight UNLESS you are changing the weight of the other components.

A 15 pound FW has 50 percent less weight that a 30 pound wheel. If all you change is the FW that's how you figure percentage of change.
Click to expand...

A 15 lb flywheel might be 50% easier to install than a 30, but dropping it will smash your fingers 75% less :)

Performance gain from a flywheel swap depends on the entire rotating assy, not just the flywheel. Swapping from 30lb to 15lb on a 440 will not net you the same performance gain as doing the same thing to a 273, as flywheel weight is a much smaller part of the 440's entire rotating assy.
 
Here is what I am trying to understand. ... Doesn't the rotational mass of an 11" flywheel have a different effect than the reciprocating balanced assembly ? The crank has a center of about 5"s and the rods are not spinning they are "stroking" for lack of a better term...So the initial post about acceleration per sec. of 2 differently balanced motors is a little misleading.
The engine with Aluminum rods and far lighter bob weight is going to react differently than if just the flywheel itself was that much lighter...? Correct ? And the test was done from a roll where as a dragstrip launch is done with RPMs up then dropping clutch. In which case I would think the built up energy of the heavier flywheel would be a benefit assuming you had enough traction.

Thats my imbalanced thinking...lol
 
mbaird said:
So are you saying an aluminum clutch will make the car more or less easy to drive on the street ? Which will be 98% of its use.
Click to expand...



I'm saying you won't know the difference but your chassis and tires will.


I'm going to go out on a limb here and say that 98.7562% of the people who say an aluminum FW isn't streetable has never used one. Most of these guys don't even have a stick.


And to say a 440 won't notice a weight change in FW compared to a 340 is abject bullshit. The FW doesn't know what it's being hooked to. It only knows stroke length and gear ratio and RPM. In fact, as power goes up, RPM goes up, as your gear ratios get lower (higher numerically) the more important it is to have the lightest rotational weight you can get. The ability to rev an engine with no load is an entirely different animal than an engine with load on it, and the two are mutually exclusive. I have seen engines so snappy when hitting the throttle that were PIGS under load.

You can get a bob weight too light. I have seen it and it took us a bit to figure out what the hell was wrong. On the dyno, the engine would pull to 8k and not even blink. In the car, the engine would get to about 6k and act like it was running into a giant headwind. We ended up changing out some pieces and th bob weight went up a bit. Same HP on the dyno, same RPM it on the track it would pull. To verify we weren't nuts, we put all the lightweight **** back in and it went back to its old ways.

There is a few of the titanium rods laying around from that deal.

Don't step on your dick by trying to make everything as light as you can. The FW is a big deal.
 
yellow rose said:
And to say a 440 won't notice a weight change in FW compared to a 340 is abject bullshit.
Click to expand...

A 15lb reduction in flywheel weight will be more dramatic in a 340 vs a 440, as the energy absorbed in accelerating the flywheel is a bigger percentage of the 340's overall power.
 
I also like the second gear "hit" of my heavy fw, and all the hits when I start splitting gears. If I were to lose that, that would take all the giggles out of shifting. The GV shifts under full power, just like an automatic, but the rpm drop is just 1500@ 6800.Makes a nice tire-chirp at 77 mph......
 
mbaird said:
Here is what I am trying to understand. ... Doesn't the rotational mass of an 11" flywheel have a different effect than the reciprocating balanced assembly ? The crank has a center of about 5"s and the rods are not spinning they are "stroking" for lack of a better term...So the initial post about acceleration per sec. of 2 differently balanced motors is a little misleading.
The engine with Aluminum rods and far lighter bob weight is going to react differently than if just the flywheel itself was that much lighter...? Correct ? And the test was done from a roll where as a dragstrip launch is done with RPMs up then dropping clutch. In which case I would think the built up energy of the heavier flywheel would be a benefit assuming you had enough traction.

Thats my imbalanced thinking...lol
Click to expand...

The reciprocating parts do not add to the effective flywheel directly, but lighter recip reduces crank counterweight required, which is part of the overall flywheel. The flywheel itself has a larger effective radius than the crankshaft, but when you bolt the flywheel onto the crankshaft that effective radius becomes an average of everything connected to it. Even the balancer/cam/timing components/pulleys/alternator rotor/distributor shaft/etc, they all contribute to the effective flywheel. The flywheel is only one part of a much larger/heavier assembly. A 50% change in flywheel weight does not change the effective weight of the effective flywheel by 50%.

A heavier flywheel can add a huge amount of pre-stored energy to your launch, but the chassis has to be able to put that energy to productive use. If that heavy flywheel makes you install bigger u-joints/driveshaft/axles/tires/etc, accelerating those heavier parts will quickly eat up all that extra stored energy and more.

I rely on clutch slip for bog free launches, not flywheel weight. Personally i want the lightest flywheel that can take the abuse.
 
AJ/FormS said:
I also like the second gear "hit" of my heavy fw, and all the hits when I start splitting gears. If I were to lose that, that would take all the giggles out of shifting. The GV shifts under full power, just like an automatic, but the rpm drop is just 1500@ 6800.Makes a nice tire-chirp at 77 mph......
Click to expand...

If that makes you happy, then that's all that matters :)
 
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