I do not know if anyone else has noticed a trend with the effects the flywheel weight has upon the life of clutch baskets and broken gears in the transmissions. I am seeing this trend in customer engines.
Basic engineering and physics supports what I am seeing,
A heavy rotating crankshaft assembly (crankshaft and ignition flywheel) spreads the power impulse delivered to the clutch and transmission over many more degrees of crankshaft rotation than lighter rotating crankshaft assemblies.
Metals have limits on the amount of stress they can be subject to before they fatigue, crack and then have catastrophic failure. Lightweight crankshaft assemblies and the increase in the torque of the big bore kits increase the spike in stress that the clutch and transmission must experience. When a metal is stressed below a certain level the metal behaves like a spring.
A prefect spring (metal) when stretched, returns back to it.s original shape when a certain stress level is not exceeded with absolutely no long term damage. When a spring (metal) is stressed slightly beyond this certain stress level, the spring will become permanently damaged and begins to fatigue. Every time this certain stress level is exceeded, another fatigue cycle is added to the count of cycles before the metal fails. If we dramatically exceed this stress level where permanent deformation of the metal occurs, we dramatically reduce the number of cycles before catastrophic failure occurs.
In summary:
As we increase the amount of torque an engine develops and reduce the weight of the ignition flywheel....... the sooner the clutch basket tabs are damaged and transmission gears may break.