RE: McCoy engines
PT:
Reasonably certain it was leaded steel, if Hank decides to make a new cylinder he should use a different alloy though, similar to what John Brodbeck used in the K&B Green Head engines. They lasted very well, and were also very similar to the Testor's sport Red Head engines in design.
Bill.
PS: Hank, maybe you can ask Randy Linsalato what alloy is used in the K&B engines. He owns the company now - MECoA. wr.