[Stan Weiss]

Originally Posted by Half-Inch Stud

both magnetos set for best cruise power, intended to fire at same timing.

Mark,
I do not know this engines configuration. But I do know from years ago working on the Chrysler 426 / Gen II hemi heads, that running the 2 plugs required less total timing than when the same engine / heads was run using only one plug. The flame front burn time is still the same but in the direct where the second plug was you now have a great distance for the flame front to travel.

Stan