Technical Flywheels... Billet Steel vs Cast Iron

I'm curious, is there any downsides to using a billet steel flywheel instead of a cast iron one? I get that the steel one is safer from a high-rpm standpoint, but cast iron is better at dimensional stability under heat, I.E., less likely to warp. Probably better at wear too. Any real-world experience on this?

 

I guess I'll see, I just ordered a steel one to replace iron.

 

We'll be waiting for an in-depth report.
I didn't spend as much time on metallurgical studies as I should have (too many girls to study...) but there is no doubt a compatibility issue between the friction material and the contact surface, same as brake rotors, so the proper surface on the steel will be important.

 

Long wear versus keeping your feet. Steel wins every time!

 

Steel is much better at wear than an iron one .
They used to make rails for the railroad from iron,,,,,but realized they wore out too quickly.

An iron flywheel is a very good piece,,,,,,they work really well.
However,,,,A steel flywheel will always out last,,,and out perform iron .

Crankshafts,,,,cams,,,,,lifters,,,,,all the best ones are made from steel .

And as for stability under heat and load and not warping.
Iron brake rotors will warp almost sideways under any real heat from panic stopping.
And about all you can do with them afterwards is throw them away .

I’m not bad mouthing iron,,,,it works very well in almost every environment.
But,,it can be overtaxed to the point of failure if overloaded and abused.
Most of the factory stuff was iron from a monetary point,,,,they already had all the foundry work and casting was fairly inexpensive,,,,,iron itself isn’t expensive,,,there are many grades of iron.
It just depends on what the OEM s were trying to accomplish in the price point .
With the factories,,,it all comes back down to pennies,,,,,,how expensive is it to produce .

No downside to using billet steel flywheels,,,,,other than the extra money they cost,,,lol .

Tommy

 

JMO, you can't go wrong with a billet steel flywheel... performance or safety wise.

 

Rotors is what got me thinking about this. All you'll find in automotive applications is cast iron unless you 'step up' and then it's a carbon composite of some sort. Wilwood and Baer both supply iron rotors with almost all of their kits. Same for cylinder sleeves, even on the fuel motors; cast iron. Dimensional stability is the reason I was given for this.

This isn't a Chevy motor, it's a stroker FE and will see 6K RPM at the max with a rev limiter. I've got two OEM flywheels, they both need resurfacing and I don't have any history on them. Neither looks particularly worn beyond anything 'normal'. Strictly street use, no racing.

 

Iron and Cast Iron are two different Irons.

 

A 6,000 rpm clutch or flywheel explosion will make a helluva mess. Why risk it with an unknown OEM flywheel and/or pressure plate, for that matter?

 

I have used steel flywheels for decades with no issues. The bigger issue is the weight. A wheel in motion tends to stay in motion. That said a heavy flywheel helps at the shift. It won't drag the engine down like a aluminum or light weight steel. The car usually goes faster with a heavy flywheel. The exception being blown very high hp cars.
Light weight flywheels work best in circle track applications. They allow the engine to slow the car down going into the curve. Check to see what's available for your engine.

 

Any cast flywheel will be challenged with rpm. There was many reasons why NHRA has mandated steel flywheels for as long as I can remember. 6000 rpm might be ok. Do you want to find out if you have a good one? I have been lucky and stupid before. I try to avoid that now.

 

Crazy Steve ,

If it’s a good flywheel without any surface cracks,,,I wouldn’t be afraid to use it,,,,for your stated purpose .
For any really hot high power application,,,,I would go with Steel !
Just for a safety margin in my opinion that is .
6000 rpm isn’t an over the top number,,,,,it should be fine if it checks out okay .

Tommy

 

How often to flywheels blow up? I always thought the pressure plate would go first! In all my racing I have never seen a flywheel blow…..but I have seen several pressure plate let go! Are pressure plates…steel or iron?




Bones

 

There is no reason not to use a cast iron or nodular iron production flywheel in a passenger car situation. Yes I race with steel flywheels but when I put a well built 302 GMC 6 in my sons street 40 Chevrolet Coupe we used a stock cast one that accepted a 10-1/2” B&B pressure plate. As for wear, an organic disc can not wear out anything unless the rivets come in contact with either of the 2 metal sides after thousands of useful miles. Additionally a centered iron or metallic disc is ludicrous on a street car.
The worst thing you can do is lighten a cast flywheel like many did with the flatheads prior to the time of the overhead valve V8’s. The flathead flywheels lived where the new higher rpm engined lightened ones did not.

 

I saw one blow at MOKAN the guy was Luckly it all went down Most pictures you see are TRY 5 Cheves

 

That's my thought too. I don't have concerns about the clutch, it's getting a new Centerforce 11" unit. I think my best bet will be to have both surfaced, then magnaflux both to make sure there's no issues. If neither passes muster, then I'll go steel.

There are new cast-iron ones available, but I'm not quite as trusting in the aftermarket ones. Chevrolets are known for exploding flywheels, it's a relative rarity in other makes.

Back in the early '70s I screwed a stroker FE together (428 crank/427 block) and used an aluminum flywheel for reasons that seemed good at the time. The upside was instant revs; it sounded like a sprint car. The lack of 'energy storage' in the flywheel was overcome by the gobs of torque it put out. Guys would pull up next to me at lights and rev their motor, I'd whack this thing once and become instantly invisible... LOL. The downside was at full cry, I swear you could feel every cylinder fire. That car developed rattles on a regular basis....

 

Magnaflux isn’t infallible however most shops can magnaflux and it should find most cracks.
Ultrasonic is another option if available and a good tech should be able to find any imperfections cracks, inclusions, etc..
Dan

 

Just to clarify, I am pretty sure that OEM flywheels are nodular iron, a much tougher material than plain cast iron.

 

Many truck cranks were too.
Referencing above SBC cast flywheels from 55-up; I’ll estimate ran over 1 BILLION miles without a failure. Sidestepping a clutch at 6000 rpm and shifting at 7500 was not covered under the warranty.

 

I prefer a wide margin of safety. Anything that gets raced, or hot rodded, or revs over 5 grand, I put in a steel flywheel. There is not a reason in the world not to. In stock applications, I check the iron wheel over very carefully and mag it.

 

I had a steel factory Chevy L88 unit in a '65 Belair, for a very short while. I didn't realize I had to use it with an un-dampened clutch disc. I should dig it out to decode the numbers. I'm not sure of the weight, but the engagement was a ton smoother when I went back to the truck unit, 168T.

 

I think the pressure plate or the clutch disk itself was the weak link but either way all you had to do was pull the pin on a hand grenade... right. If yer gunna spin yer shit up high, have some good parts under yer feet

 

GM reportedly did some flywheel testing on their nodular iron flywheels and they were very safe and strong. They did note that overheating them due to slippage did cause some weakening. I'd think that as long as the clutch is gripping instead of slipping in a street machine that nodular iron should be fine.