12 volt coil on a 6 volt engine

[Growley bear]

Ballast resistors were introduced at the onset of the use of 12 volt systems mostly in 1956. Ford used all three types at different times. The reason for ballast resistors in a 12 volt system is that the longevity of contact points is greatly shortened when used with 12 V. The resistor keeps the points from self destructing which they will in short order if run on 12V. 8V is border line 12V is unacceptable.

Chet