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?
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.
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
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.
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 cintered 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.
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.
Hello, My brother and I had built up a 283 SBC motor with an Isky Cam and Kit. Assembly was like a giant puzzle and we did it the specific way he wanted to put it together. His list was specific and we set up the long counters/work table with the clean parts ready to be installed in the way he wanted it done. We finished it and rolled it to the real two car garage pulley lift space. Once the motor was jacked up the whole Willys Coupe was rolled in place and the motor dropped back down into the installation point. When we rolled the installed motor and car back to the backyard garage area, it was ready for the final installation of the rest and we would be able to fire it up. Soon, the motor rumbled fine and we took it for a drive around the neighborhood. No full throttle shows as it was a warm up and we just wanted to feel the motor as we went through the gears and on the road. Plus, the open Hedman Headers did point the center of attention on us as we rumbled down the street. Jnaki It had the original steel flywheel and it ran fine. But, when my brother had bigger ideas for our Willys Coupe, we took the motor to Reath Automotive to get it stripped and modified to support a larger bore and prep everything for a supercharger addition. So, we purchased all blower spec parts + Reath’s famous hard chrome crank for the now larger 292 c.i. SBC block. Being a Howard Cam fanatic, my brother purchased an all aluminum Howard Cam Flywheel for our last build of 1960. Some typos from the harried secretary at the Drag News office... 292 C.I. 37 LaSalle, Howard aluminum adapter, 56 chevy rear end, 40 Willys motor and running gear etc... All parts were sold to So Cal racers. The 671 SBC motor complete, sold within one month. Sold to a Midwest hot rod/drag racer, who flew to So Cal to buy and ship it back home. YRMV
Here in Sweden we have a form of relatively cheap "junk car" racing, where you are allowed to tune the NA engines as much as you want as long as you stay with NA, but all cars are for sale for a fixed price after the race. The result is obviously that everyone wants the most performance from the smallest cost, and lightened stock flywheels are very common. They do come apart every once in a while, especially when someone without experience has lightened a bit too much in the wrong places, or lightened an unsuitable type of flywheel. I wouldn't worry too much about unmodified flywheels in good shape at stock rpm levels, but once you are tuning the engine the circumstances change a lot.
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