This is what Andover Norton say about their camshafts:
Andover Norton camshafts, and around 90 % of all production car camshafts, are made from “Chilled Iron”. Chilled Iron is around 25% better than normal case hardening steel and around 15% better than nitrided steel at resisting wear. This materials ‘wear scuffing factors’ give the camshafts longevity and improved wear characteristics over even original Norton production camshafts. It works better than other materials due to a matrix of carbides being formed when cast. The cam lobe shape is formed by the metal chill casting process; when the molten metal comes into contact with the cam lobe areas of the casting it changes the structure of the iron to form a matrix of carbide approximately 4 mm deep. It all comes down to “Tribology”, which is the interaction of surfaces rubbing together and the scuff resistance of the materials that are rubbing together. When Jaguar were sports car racing they had repeated failures using nitrided tool steel camshafts. They began using chilled iron camshafts and never had another failure
Jim, please explain why you do advise against chilled iron camshaft for a Norton?