Spark plugs. Why is it so hard?

448Scamp.

I knew I had seen advertisements for NGK Copper plugs from my motorcycling days.
Went through some old magazines & this ad was on page 11 of Cycle Guide magazine, July 1969. 'Exclusive Hear-of-Copper guarantees the widest heat range. Cuts tip erosion & fouling...'

The Jerry Reeves link says towards the end. 'Lets look at some facts that support fine wire plugs are a good choice for a performance engine..'