[njk53]

The steel cranks that were used for production back in the day were satisfactory but, you have to remember, they were designed for heavy duty passenger car usage. The forgings could have contained small stress cracks that would never amount to anything under ordinary passenger car usage. Now you are stressing the crank even worse now with a violent twisting action on launch and spinning the crank 7,000 rpm producing harmonics the crank probably has never seen in it's lifetime. The fact is these small stress cracks could have developed into big cracks through fatigue over the years and eventually resulted in the catistrophic failure you experienced.

Another thing, back in the day, crankshaft forgings were not an exact science and the forging process was crude at best. Metallurgy has also significantly changed over the years. The steel recipes have improved dramatically.

I was just recently reading that Eagle now manufactures a cast crank that is as good or better than a factory steel crank.