I have a 1949 F-2, 6 volt, positive ground. Does the wire from the distributor go to the positive or negative terminal on the coil? Thanks.

 

The points ground the coil, so the wire between the two connects to the (+) terminal.

 

Were coils marked differently though, pre-56? That is, a coil manufactured after the switch that would be correct, but otherwise?

 

The coils were marked the same, + and -. They were not marked as either side being the ground.

 

To be clear, what I mean is, did coils before the switch have the terminals reversed compared with negative ground versions?

 

I think you will find that it doesn't really matter because the primary windings of the coil are isolated from everything. There used to be talk that metal would transfer on the point contacts to the electrode side if the polarity was reversed on the coil, which is true. However, with the correct polarity, metal would transfer to the anode side of the contact points. You get to pick your poison - which side of the points do you want to file?

 

Maybe, but were they marked differently pre-56?

I heard it will affect the plugs. Easy enough to check:

http://mgaguru.com/mgtech/ignition/ig104.htm

"Why then do we worry about coil polarity? Because the spark plugs do care which way the electrons are flowing in the high tension circuit. The spark plug has a thermally insulated center electrode (surrounded by ceramic). With engine running the center electrode runs substantially hotter than the exposed end electrode. Design of the ceramic insulator determines how hot the center electrode will run, leading to the designation of hotter or colder spark plugs. As electrons go, they love to jump away from a hot surface and fly toward a colder surface, so it is easier to drive them from hot to cold rather than from cold to hot. End result is a difference of 15 to 30 percent in voltage required to make spark "initially" jump the gap on the plug depending on which way it is going."

 

Yes. With reversed polarity the anode becomes the sacrificial lamb instead of the electrode, which makes it difficult to re-gap the plugs.

 

Thank you!

 

Naturally just had to check the coil in the slick last night. All is right with the universe, ha ha. The pencil trick sounds a little sketchy to me in terms of getting zapped, so used analog voltmeter connected as shown between the high tension lead in the coil, and ground. The takeaway is to disregard whatever markings are on the coil (if necessary) to get it right - look for an upward swing in the needle on the voltmeter, if you don't get this the coil is hooked up wrong no matter what the terminals are marked.