Rocker Arm Studs. I forgot to say, failures with some carbon steels are because they were heat treated to hard. This makes them very brittle. There is a fine line between hardness and toughness. You want both in a valve train or bolts. Too hard, hardware breaks. Camshafts and solid tappets are heated treated to a Rockwell hardness in the upper to lower 50's. If you have ever seen sheet metal punching dies, their hardness is in the 60's Rockwell, C - Scale. They are super hard so the punch and die can make thousands of parts without having to be resharpened. As Paul Harvey would say, here's the rest of the story. VET
