Back in the sixties, the nylon tooth cam gear was what was used on the Pontiacs and others. Supposedly it was for silent running. Do a bit of higher rpm running and the gear wouldn't last 30K miles. This happened to my '68 Ram Air Firebird. The standard replacement timing set was, you guessed it, steel/cast iron, and it was just as quiet as the nylon. Never had another problem and any engine I put together, I always looked for an all metal cam gear. I'm not a big fan of aluminum either. In my trade at GM too much of my work was repairing aluminum equipment. If you are making anything out of aluminum, you might as well use Helicoils or Keenserts in all the threaded holes. If you don't, you will.