where exactly does the spark occur on the rotor bug? is there a certain spot or does it spark all of the way through?

 

the rotor is charged with high voltage from the coil.. as it spins inside the distributor, it comes in contact (or very near) the points on the distributor. the energy then arcs across the rotor to the point(s) in the distributor cap, which then travels down each plug wire to the plug.

 

i was just curious when it actually sparked because the metal piece that runs close to the distributor contacts is quite big.

 

it's big, but curved, more curved than the inside of the distributer, if you have an old on, you can see where it does it's thing.