Re: Sub Frame Damage
 

Another thing to keep in mind about cast iron is that it doesn't propagate fatigue cracks like steel does. After cast iron exceeds 1,000,000 cycles (which doesn't take long for a crank shaft) it has unlimited fatigue life. Steel, however, is always suseptible to propagating (growing) cracks. The bottom line is that steel has higher yield strength, but old steel cranks can have some pretty bad fatigue issues - and don't assume that small cracks that show up on crack detection will stop growing.

Re: Sub Frame Damage
 

A little JB weld and that block will be good for another 100k miles. [img]<<GRAEMLIN_URL>>/wink.gif[/img]

Re: Sub Frame Damage
 

I had a Nova drag car I shifted at 7k with a cast crank. Never had a problem. Detonation is what kills them whether a cast or forged.

Re: Sub Frame Damage
 

At some point horse-power and stress can cause trouble. I believe that a forged crank and four-bolt block can take more.