[Cman60]

Stocker, typically yes, but I've seen it where the main spring breaks and the secondary spring (if equipped) will operate the valve at low rpm. The noise won't appear until higher RPM.

I've also seen (don't recall if it was GM or not) , where a slow operating (lazy) valve can get kissed by the piston, causing a noise. Often diangnsitics are a matter of a process of elimination.

Certainly do the easier stuff first. Sounds like you're on the right track. Also the bare ignition wires could be cross firing, casing the timing to be off on the affected cylinder, causing the ping (pre ignition).

Interested to know what you find.