Flywheel Surface Cracks
 

I'm just in the process of reassembling my Cobra after addressing a pilot bearing problem.
While I was cleaning up the flywheel before bolting it back on, I noticed numerous very fine surface cracks where the friction plate makes contact.
Should I be concerned or is it normal?

Thanks,
Paul

Hi Paul,
You have a stock cast iron flywheel. It is common for these cast flywheels to have heat cracks in them. They are cracks and should be fine for mild performance use. If you are going racing or drive it like a racecar (shifting at redline often) then I would replace it with a steel billet or lite weight aluminum billet flywheel. I sell & stock both flywheels if you need one.

Have it resurfaced then check for cracks, if their too deep, throw it away. It's not worth injury !

If there's any bluing, that means clutch slipping and has gotten very hot.
Some people just can't stay away from slipping the clutch. I've seen many people at red lights, and rather than putting it in neutral and using the brakes, they ride the clutch instead ?? :rolleyes::JEKYLHYDE

Compared to the cost of failure, a replacement billet steel unit is cheap.

After I saw that video of the non-cracked iron flywheel coming apart on the dyno, I think I'd swap it for a steel one.

Depending on what size pressure plate you're running, it could be real cheap and easy to swap at this point.

Are you going Kevlar??
 

FatBoy Paul you can resurface a flywheel 1 time. If you are getting alot of surface cracks, this is normal with a little abuse. If you stay with an organic disc and basic clutch setup this flywheel should be ok. If you are looking for a more agressive clutch you need to look at either a steel SFI rated one or go to an Aluminum one with steel insert. These are rebuildable. The problem is alot of heat builds up in the bellhousing and there is no where for it to excape too. The more metal or kevlar in the disc the more bite it will get when hot but also the more heat the flywheel has to absorb and this causes the heat cracks. IMO and I run a lakewood bell, go to an aluminum flywheel that is SFI rated. I do leave out the boot to the fork to help remove some of the heat from this location. It does help a little. Rick L. Ps make sure that bushing is flush with the back of the crank and recheck the end clearance. There should be a little play on the input. Not shore about what 1mm is in inches. It might be easier to just replace the bearing and seal and know its fixed and forgetaboutit. This is what I would do. When you get the new clutch in the car break it in easy for the first 500 miles. You have new materials and surfaces that need to get used to each other. It's just like breaking in new brakes, same thing. Too quick and you glaze everything or burn surfaces.

Bill at Southern Automotive is sending me a new steel flywheel free of charge. :3DSMILE:
You really can't say much fairer than that. I didn't even need to ask him, he just told me that was what he was doing.
Well done Bill. ;)