Hi Chris,
Maybe it would be ok to think of the coil as a 5 gallon bucket which needs to be filled up as quickly as possible. And you have two means: one is a fire hose and one is a garden hose. Obviously the fire hose is the one to use. Unlike a capacitor which also holds a charge until needed, the coil increases voltage and without that coil (or any coil for that matter) being charged fully the ignition system won't work. And as Jerry correctly pointed out it must be charged repeatedly with each conduction cycle. But...it doesn't have to be charged fully with each cycle. And that's why it takes less amperage when the engine is running. It is sort of like a swamp cooler that uses a float to fill the reservoir when evaporation depletes it.
My idea of using 10 ga wire was that it would be like a larger fire hose. More comfort in my mind that the coil would be charged very quickly when the key was turned on. And GM knew that had to happen or 12 ga wire wouldn't have been used.
As for the sizes of wires, here's part of a guide I found and saved which may be helpful (I won't go all the way down to 2 gauge but will start at 10 gauge):
10 gauge for as much as 150 to 200 amps at 3 feet or less, 100 amps for runs of 7 to 10 feet, 30 to 50 amps at runs of 15 to 20 feet and 20 amps at runs of 25 feet.
12 gauge for as much as 100 amps at runs of 3 to 5 feet, 75 amps at 5 to 7 feet, 50 amps at 7 to 10 feet, 40 amps at 10 to 15 feet, 20 to 24 amps at 15 to 20 feet and 15 to 18 amps at runs of 20 to 25 feet.
14 gauge for 50 amps at 5 to 6 feet, 40 amps at runs up to 7 feet, 30 amps at up to 10 feet, 15 to 18 amps at 15 to 20 feet and 11 to 12 amps at runs to 25 feet.
16 gauge for 50 amps at up to 3 feet, 30 to 40 amps up to 5 feet, 18 to 30 amps at 7 to 10 feet runs, 8 to 12 amps at 15 to 20 feet and 8 to 10 amps at runs up to 25 feet.
So, 14 and 16 gauge wire sizes allow for lots of different uses and as you can see can handle decent amounts of amperage.
Was the ignition switch worn out? I can't say...I haven't taken it apart yet but I saved it out of curiosity. It was 40 years old, but I should add it had not been used every day or even every week for 40 years and there was a period of over 15 years where it sat in the garage and wasn't used at all. So I'll be surprised if when I take it apart I find abnormal wear. But would wear to the contact points or loose contact points have reduced their amperage ability? I would say it is reasonable to think that, but it is hard to say (or know at this point) how much. It was however a good switch, made in the USA, heavy case, heavy bakelite back and all that. Hopefully this is helpful.
