what flywheel

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twayne24365

twayne24365

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going to buy a flywheel this week and was looking at the McLeod billet steel unit but wondering what others are using.
it's going to be a street strip deal, 10.4:1 383, shift at 6500, McLeod super Street pro 10.5" clutch
 
I'm interested in this as well, maybe some of the technical editors can explain when to use steel vs aluminum and why.
 
Street strip, road race: aluminum.
Street only: Steel.
 
If you are running a starter gear of 2.66 x 3.55 =9.44, or less, then your engine will want a heavy flywheel so you can get moving without stalling it.
If you are running a starter gear of 4.56 x 2.66=12.12, or more then you could run a lighter flywheel.
Between these two ends, namely 9.44 and 12.12,It would kindof depend, on the engine. If it has plenty of torque right off idle, then you could use the lightweight. If you have over-cammed it and the bottom sux, then you better stick with a heavier one.

This is based on my experience. You are of course,free to choose whichever,and see how it goes.

There are really only two reasons you use a lightweight; 1) is cuz you can,re the starter-gear, and 2) is cuz it takes less horsepower to spin up.
There is really only two reasons to use a heavy flywheel; 1) is cuz the engine needs it for take-off, and 2) it helps smooth a jumpy tune.
At the racetrack, a heavy flywheel can help get a little engine in a heavy chassis moving lickitysplit.
I prefer a heavy flywheel and a 10.97starter gear. With a mild street cam, it's a dump-it-and-go take-off.
The bigger flywheel also tames the power pulses when you drag the engine down to the stall-zone, cuz Billy-Bob is trying to have a conversation with you, outside the car, and you just really wanna go home.
 
There is almost no reason to run a still flywheel. Unless you are running a 3.23 gear or something.

Even a 9.0:1 overall first gear will like an aluminum flywheel.
 
well lemme say what street strip will be mostly street with a trip or two to the track a year, the motor isn't some torque monster, it really starts coming on at about 4000-4500.

would a good trade off be a lite weight steel?
 
I have run a McLeod street strip dual disc unit and will never go back to a single disc, granted they are a grand but in my opinion worth every penny.
pedal is very easy to push, never slips, will take 1000 plus hp. The only clutch that I liked that was a single disc, I had good luck with was a Hays racing 10.5" but don't get stuck in traffic your leg would fall off.
 
twayne24365 said:
well lemme say what street strip will be mostly street with a trip or two to the track a year, the motor isn't some torque monster, it really starts coming on at about 4000-4500.

would a good trade off be a lite weight steel?
Click to expand...

Lite steel is very forgiving and a great choice. You get most of the lower moi benefit of an aluminum flywheel, but with much less tendency to warp and a lot less flex.

On the racetrack aluminum generally revs quicker and absorbs less power as the revs go up, but it also returns less power after the shift so it doesn't recover as well as steel. A little slippage after the shift can greatly improve recovery, but with aluminum you have to be careful as less thermal capacity means it's a lot easier to overheat/warp the insert.
 
twayne24365 said:
well lemme say what street strip will be mostly street with a trip or two to the track a year, the motor isn't some torque monster, it really starts coming on at about 4000-4500.

would a good trade off be a lite weight steel?
Click to expand...


Yes a light weight steel would be a good middle of the road pic. 30 pounds is just too heavy.
 
Aluminum flywheels are usually around 15lbs and steel ones 30lbs. Who sells a lightweight steel one and how much do they weight?
 
yellow rose said:
That's about a 38 percent reduction in weight. When thinking about it,,that's a significant percentage.
Click to expand...

It's about 38% if you are comparing 11lb vs 18lb flywheels only, but less than 7% when you consider the effective "flywheel" is actually the entire rotating assy.... crank/balancer/pulleys/flywheel/pressure plate
 
I'm a dump it and go kinda guy. Probably 80 plus % of the time, I just blip the throttle and dump it.. I like to do it, cuz the engine can do it. I have never had anything but the factory stock flywheel,in this car. I have driven cars with aluminum flywheels and track gears and that was great. I have driven streetcars with aluminum flywheels and street gears,and that was too much like an old 5.0Mustang for me.I wouldn't be able to live with that.
Remember that I have a 10.97 starter gear which is 3.09 x 3.55. If you have a regular A833, this would require 2.66 x 4.10s.
In all likelihood most guys will have a 2.66 x 3.55 for street, and that gets you a 9.44 starter gear, which is a 16% reduction, and so will require quite a bit more revs to get the same brisk take off. A light flywheel will require a more careful pedal modulation to make this a smooth endeavor. A dump it and go will be an automatic stall.
Another neat thing with a heavy flywheel, is I can do tricks. During the dump-it-and-go routine, if I blip the throttle just right the car will kindof jump off the line, which is always a surprise to the guy in the next lane. And I get just a little squawk out of the tires. I think with an aluminum fw that would be an automatic stall. Stalls at green-lights are really embarrassing.
If you have a lot of cylinder pressure, the heavy fw can tame the idle and especially so when driving in first gear,really slowly.The power pulses at low rpm can be pretty strong, and if the butterflies are not on curb idle, your gas-foot can start to do a little dance on the pedal and that goes straight into the chassis, and the car starts jumping to the point that you have to depress the clutch to settle the chassis.I can almost guarantee you that a 360 with a 9.44 starter gear, a 230* or bigger cam, 165psi or more,and a 750rpm idle;you will have slow speed jumpiness. A heavy flywheel can help to ease or perhaps eliminate this nonsense.
If it seems like I am a big fan of a heavy flywheel for a streeter,that would be cuz I am.There was a time I thought about running a lighter one. But the thought only lasted a few seconds. I'll put it this way; I've never been sorry for having the beast in there.
 
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AJ, I am running 4.56 gears with standard ratio so 2.66x4.56 so 12.13 starter gear.
also the motor doesn't have crazy low end power, at about 10.4:1 and a solid cam at [email protected] it probably doesn't have a huge sum of cylinder pressure, when I was running the automatic"which definitely needed a rebuild" the converter flashed to about 3800 and once it hit 4200-4500 it pulled hard up to 6500 when I would shift.

correct me if I'm wrong, but my thinking is the lighter flywheel will "soften" the hit and let the motor rev slightly faster to get into the powerband. and I don't want aluminum but talking about the light weight steel.
 
HaH!!
If you are running THAT on the street you can run anything for a flywheel!
Seriously.
But I would still run the beast.

And here's why; in about 500 miles or less, you will figure out that 12.13 is ridiculously low for the street. And 4.10s or 3.91s are gonna find there way in there, and then that big cam is gonna want some flywheel.heehee. So you can save yourself the headache of pulling the lighter flywheel right from the get go! I ran your numbers and get a Dcr of about 7.9 at 156psi. So yeah with 3.91s you'll feel the hole. 4.10s not so much; but the heavy fw would provide relief with those,during initial engagement. This is why I run the deep low in my box.
But, on the off chance that the 4.56s are in for the long haul,you can run anything. You have enough starter gear for aluminum. Flip a coin,as to aluminum or middle-of-the-road steel.. You don't need heavy.
As to power;IMO I doubt you will ever see the difference. Yeah it will make a difference at the track. But a streeter has about a 65 mph speed limit. That is usually a one gear run. Not so much for you.With 4.56s it maths out to the top of second gear.And the biggest problem for a streeter is hooking. Zero to 60 is somewhere between 5 and 6 seconds for us. So even if your engine reved 2% faster.............would you see it in the time slip?
I'm more interested in the vast majority of city driving which involves a start from zero mph, than the minuscule percent of the time I actually need to win a sprint. I only have a 367 with maybe a tad over 400hp. I am geared for 65 mph =6900rpm in first-od (with a GearVendor). 295s spin the whole way. I don't care one tiny bit if my engine could make a teensey bit more average horsepower, cuz I can't make use of what I already have. And I like it this way. I'm not in it to win races. I'm in it to have fun,and try to suppress the urge to giggle.Grown men should not giggle, right. heehee....
Yeah so,if you got your eye on a lighter fw, just go for it!

But I tell you what; if you have not yet driven this combo with the heavy flywheel, and you have one,I highly recommend that you do.Then you can make an informed decision based on real-world experience.
 
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I certainly don't do any highway driving, just around town, to the stores, and home. hopefully trailer it to the track a time or two a year. I just kinda thought the lightweight steel was kind of the best of both worlds being in between
 
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 ?
 
What AJ said about a car being jumpy at initial clutch release is interesting. I have driven new cars in the past that tended to do that and I always attributed it to weah throttle spring.... it never occured to me that it could be fly wheel weight.
But that makes perfect sense ! I ride dirt bikes and flywheel weight varies depending on use and engine size... it can really change the personality of a bike.
 
I had two engines that were pretty close to identical but with different component weights. The weight of the flywheel itself didn't change (both used the exact same 17lb steel flywheel and RAM PP), but i did change the "effective flywheel weight" of the entire crankshaft/flywheel assembly with lighter crank/rods/pistons...

...Engine #1 was 4.04" x 3.48" w/ 5.7" i-beam rods, hypers with gas ported spacers and 1.2mm rings (12lb oil), 49lb crank balanced to a 1863g bobweight.

...Engine #2 is 4.03" x 3.48" w/ 6" aluminum rods, forged pistons with lateral gas ports and 1.5mm rings (14lb oil), 42lb crank balanced to a 1492g bobweight.

Both had flat tops with nearly identical quench and compression. Same intake and carb, same carb calibration. Exact same cam installed on the exact same intake centerline. Same flywheel and pressure plate installed in exactly the same car, same weight, with exactly the same gearing and tires. Even though these tests were a couple weeks shy of 2 years apart, both tests are on the same location with zero tire spin and conditions were very close to the same.

Here's the observed rates that the engines gained rpm WOT...

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)
2nd gear 4000 to 6000 rpm- engine #1 1070 rpm/sec.......engine #2 1116 rpm/sec (46 rpm/sec difference)
3rd gear 4000 to 6000 rpm- engine #1 535 rpm/sec.........engine #2 541 rpm/sec (6 rpm/sec difference)

As you can see, in the higher gears where acceleration is slower there is not much difference in acceleration rate. But in the lower gears, the differences in rate of acceleration progressively increase.

There also seems to be a quite a difference in no load acceleration rate, but the conditions of the comparison were not the same. I had a clutch linkage experiment go bad in 2014 with engine #1, which resulted in a free-rev condition during a 4000 rpm WOT launch in which that engine gained rpm at an 8500 rpm/sec rate. I was also experimenting with pulling timing at the time for an upcoming no-prep race, but my records don't indicate that i was pulling timing on that particular launch.

Under NA free-rev conditions, engine #2 gains rpm at a 11,515 rpm/sec rate.

All acceleration tests are basically inertia dyno runs, even if that test is a no-load test where the only inertia resistance is supplied by the weight of the rotating assy itself. What most people lack is a way to collect accurate comparable data. Even though these tests were conducted almost 2 years apart, the car itself was basically a time capsule...engine #1 blew up a few weeks after the test, and i had other irons in the fire so the car sat until engine #2 was ready to install a couple years later. I was just picking up where i left off with regard to developing the car. To me the part that said the gain was because of the lighter rotating assy is because the closer the two engines got to steady state power production, the closer the power outputs were. By 3rd gear, there was only a 6 rpm/sec difference. Sorry, no 4th gear data available to compare from engine #1, that test area just isn't long enough.

Something to think about- if measuring reduced inertia acceleration gain from 1000 rpm, it would be hard to tell much difference. But the gain is exponential...any acceleration gain you get from reducing the weight of the rotating assy at 1000 rpm is magnified 49 times by 7000 rpm. Spin it to 8000, that gain is magnified 64 times.

In my street/strip car i want as light of an "effective flywheel" as practical, but even though a lighter aluminum flywheel would allow my engine to accelerate faster, i feel there is more overall gain available in using a lite steel flywheel. Basically, more thermal capacity allows slipping the clutch longer without overheating...which in turn allows me to raise the engine's average rpm...which makes it possible for the engine to produce even more power in a tighter time frame. More than enough power production gain to offset the loss of using a heavier flywheel.
 
Ok... after that I have what is going to seem like a stupid question....
Isn't there a difference between the rotational mass of the flywheel and the reciprocating mass of the rod weight ?

I would like to see the same test performed with same motor and different flywheels.
 
mbaird said:
Ok... after that I have what is going to seem like a stupid question....
Isn't there a difference between the rotational mass of the flywheel and the reciprocating mass of the rod weight ?

I would like to see the same test performed with same motor and different flywheels.
Click to expand...


Lighter rods/pistons mean less crankshaft counterweight.
 
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