do you mean the pick up coil? that when the pick up on the flywheel goes pass the coil it causes an electromagnetic field that cause electric current to travel to the spark plug.
lots can be learned by buying up jugs by other builders. everyone has a little different way of doing things as well, so its nice to see different perspectives on how they make power. i've always wanted to get a flotek top end, wildcard, oconnor, and even kennedy top ends to dyno back to back.
before school i didnt know what a micrometer was then lol