Buzz coil question (Tom Thumb)

[Harry]

On the older non Ford type buzz coils in a box, there are generally four connections. Two on the front side for the primary through the points and two on the top for the secondary.

My question is: which is which on the secondary terminals? Obviously one goes to the spark plug and one goes to ground, but does it matter which one? I'm sure some of the old coils were marked with labels on the wood, however, mine is plain.

One spark terminal is toward the top front point side and one toward the top rear. Maybe it doesn't matter and maybe one was the outside of the coil winding and one was from the inside. I would think the outside of the winding should go to the spark plug.

Was there any standard for locating these?

[Jim Sherman]

See the picture here if this is the type of coil you are talking about. I used a jumper on the front top post to neg side. The back top post I put to the spark plug. I can't remember where I found this info but it works great.

[Elden DuRand]

Originally Posted by Harry

Which is which on the secondary terminals? Obviously one goes to the spark plug and one goes to ground, but does it matter which one? I'm sure some of the old coils were marked with labels on the wood, however, mine is plain.

Hi Harry:

Use either one and ground the other. If you have an even firing two cylinder engine, just run each end of the secondary to a plug.

Take care - Elden

[J.B. Castagnos]

As Elden said it should work either way. Until the wasted spark systems became polular, where they fire both plugs at the same time with the spark on the exhaust stroke being wasted, it was thought that the spark should jump from the center electrode to ground. On these systems it has to go in one plug and out the other. To find out the direction the spark is traveling you can hold a pencil point in a gap and let the spark jump across it. The downward side will have a sparkling trail by the graphite it carries off with it.

[BWegher]

There is no electrical component with polarity, condensers work both ways.
The direction of high voltage does matter. The spark plug center electrode is designed to withstand erosion. If you run the spark plug backwards, the ground electrode will degrade, just like EDM.

[Harry]

Thank you for the ideas! I'm wiring up the Tom Thumb today.

The "wasted spark" type of coil sends a huge flame to the spark plug!