Coil Hooked up Backwards...is it bad?

I've been told you can loose upto -40% of your sparkies with incorrect coil polarity. I personally have seen -25% loss at ignition school when demonstrating incorrect coil polarity.

And NO, incorrect coil polarity doesn't hurt the coil, just the sparkies. And as a general rule, your 1-nipple roundcan ignition coil is fairly bulletproof.

Bottomline, when your ignition points are worn and corroded and your sparkies gap is worn wide and carboned, you'll have trouble starting. But then, you really need a tune-up with new ignition parts ennyways.

Iff'n you found your sidemount thru terminal shorted and you still don't gitt enny sparkies, guess what? your still shorted somewheres 'cuz you ONLY gitt sparkies when the points OPEN and iff'n yer points wire is still shorted the coil will NEVER make sparkies even iff'n you can see your point opening and closeing..... ....Dell, the self-appointed sparkie-meister

The loss of EFFECTIVENESS of a reversed-polarity spark is due to the fact that because of "thermionic emission" you want the leading edge of the high-voltage spark to the thermally HOT center electrode of the spark plug to be NEGATIVE with respect to the cooler "ground" electrode.

Obviously, this would have to do more with avoiding missfire once the engine is running, because from a cold start, there is going to be no thermal advantage to the center electrode.

Bottom line, with the coil hooked up properly, you should have a better RUNNING engine, but I can't see where it matters at cold startup.

Inside a round can coil, one side of the primary winding and one side of the secondary winding are hooked together. That's the side that needs to go to the distributor. BUT, there ain't no way to easily tell which side that is!

For most coils marked with a "+" & "-", that side would be the one marked as "-". Before negative ground systems came along, coils were marked with something like BAT and DIST or some such. The BAT terminal went to the battery regardless of polarity and the DIST side went to the distributor.

If the other side of the coil is hooked to the distributor, then the secondary winding will be firing through the primary winding, which will weaken the spark somewhat. There probably even will be a reverse secondary voltage induced in the secondary coil which wouldn't be good either.

Now, what I'm saying is to hook the "-" terminal of the coil to the distributor. But, Dell will be along shortly and probably say why you shouldn't do that!

Test it both ways and see which way gives a hotter bluer spark.

Soundguy

• The Ignition System

That brings up a good point. The markings, "BATT" and "DIST" are MEANINGLESS on a coil unless there is a part number on the coil, or you are otherwise CERTAIN of it's original intended use.

A coil marked "DIST" and "BATT" originally intended for a negative ground system would be labelled directly opposite of a coil originally intended for a positive ground system.

I have several ignition oscilloscopes, and have more than once verified these differences in actual operation.

The interesting thing with the ignition 'scopes is that the actual polarity if the display is "flipped", so that the negative-going leading edge of the spark is display as RISING vertically, which makes it easier for the average mechanic to view the firing voltages of the plugs in firing order and relate them to each other, for troubleshooting.

Soundguy

Like I said earlier, the post that is commonly connected to both windings inside the coil should go to the distributor.

There are Ford coils from the (+) ground 50's, and (-) ground 60's, 70's, and 80's labelled (DIST) and (BATT), and there's GOT to be a difference between them.

I believe the important thing is spark polarity at the plug, not which terminal serves as the common between the primary and secondary windings. The is such a difference in the turns ratio between the primary and secondary windings, and such a difference in wire gauge, and resistance (and impedance) that the difference there is all but negligable.

Most all the mechanic's references I've ever seen from the point era refer to the spark polarity at the plug as the determining factor in how the primary of a coil is connected into the circuit.

I have never been brave (or stupid?) enough to use the method often illustrated in the texts of holding a pencil with the point in the path of the high-tension spark, and observing which way the sparks fly. The ignition 'scope is a bit safer!