Back in the mid 70"s the head of a Ram IV valve stock valve broke off and damaged the combustion chamber of a 722 head. After asking many racers and machine shops I took the head to Indy Cylinder Head and they repaired it. So way back then I learned,.the hard way, do not trust Ram IV valves even with flat tappet spring pressures. I don't know if they still repair cast iron maybe another member does.
