I seem to remember a special gap-setting fixture for those aircraft plugs- - - -one that used a cone-shaped device to move all the ground tabs in or out equally. The 28 cylinder radial engines on the big planes had 56 spark plugs- - - - -two per cylinder, and two complete magneto systems. 224 plugs on a 4 engine plane!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!