[Half-Inch Stud]

Ahem, so in the V8 pursuit of exceeding 2.3 hp/cid, the notion of dual spark plugs comes to my mind.

a pilot was telling me about the rpm change you can hear when checking ignition to the spark plugs. Prime plug or redundant plug will both run a lower rpm than both plugs firing.
So that says something about the wet chemistry within a big bore.

Has there been PMD heads that have investigated dual sparkplugs?

not like a 2nd spark plug doubles the HP, but that would be a funny on someone, someday.