Eagle Forged Stroker Crank CRACKED
That looks like a cast crank. What formula of iron did they use? Nickel, chromium, etc. can be added to the pour to make the product stronger or tougher; but are expensive.
The problem I see is the thickness of the web at the point of failure. I compared it to a factory 340 steel crank. The factory crank is much thicker [stronger] at that point.
