....So distributor shaft is at
engine RPM x2 since it does 1/4 revolution for distributor each piston
stroke?

Nope. Distributor turns at 1/2 crank speed - One ignition event every
180 degrees. Remember; it's a 4-cycle, so it takes two complete
engine revolutions for all four cylinders to fire.

Mike's numbers & mine look different because he's looking at individual
ignition events, & I'm looking at the low-voltage side of the ignition coil=
..
Adjusted for RPM, it's the same deal.

 Jack
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