Heh! 2 spark plugs per cylinder always makes me think of the Pratt & Whitney R-4360 Wasp Major used for the piston engine power for the B36 Peacemaker strategic bomber, AKA “aluminum overcast”.
That thing had 4 rows of 7 cylinders, 28 jugs! So a “tune up” involved changing 56 spark plugs on *one* engine, and there were 6 of them on the aircraft, so 336 spark plugs to be changed! Also 336 valves to check tolerances on and perhaps adjust.
Planes use multy plugs for safety to pervent a stalling more so then performance many went down before someone came up with the idea.
Side note disk brakes were used on the late 20’s cars didn’t get them until the early 70’s
exchange of ideas works