I was always told it had something to do with the specific iron makeup, as far as nickel content, etc. But I have no way to verify that. Might be something to it, or it might just be a legend I've heard for nearly 40 years.
May be related but I read somewhere that cranks 360 cranks with CFD cast into them were stronger than the ones with AAWJ and that CFD represented a GM foundry!
