I'm NO electronics expert but from what I have read elsewhere about the coil failures is a coil that doesn't use an external resistor/resistor wire has the resistor built in and that adds to the heating problem. If you had a true 12V coil it would have to be the size of a toaster or larger. Maybe Pertronix better idea was having them built off shore! This may be another case of vendors that don't give a damn about customers and are only concerned with how much money they can make.

(1) Coils are made of wire wraps - depending on the gage of the wire (and its alloy) it will have a resistance based on so many OHMs per foot of wire. if you want more or less OHMs - you put more or less feet of wire in there. Or you change to a wire with different OHMs per foot. I don't believe any of them actually have a "resistor" hidden inside to adjust the OHMs. It is a designed length of wire of a fixed rating - longer / shorter/ more resistance per foot - or less. .
(2) To put energy into a coil of a given number of OHMs, you feed it a Voltage and AMPs flow according to "OHMs Law" (volts equals amps times ohms) - and on our engines, you leave the circuit closed for a given interval - the DWELL. The Volts times the Amps is WATTS - and that will be HEAT energy. So if you take a low OHM coil and feed it 13.5 Volts and leave it on for 23º dwell there is going to be a temperature rise - a larger rise than if you have a higher OHM coil at the same 23º. To hop up an engine in my youth - we would put a dual point distributor on there, therefore jack up the total dwell and get a "hotter" ignition - with the very same coil. The Ford "Duraspark II" factory electronic controllers have exactly the same dwell as a set of well adjusted single points - but it never changes - no wearing parts.  
(3) If you are going to build a "hot" coil - the insulation rating of the wire becomes important. Older model coils were oil filled - and the oil was supposed to soak the heat away to the cover shell, where it is radiated away. Keeping the wire inside well covered - made sure there wasn't a "hot spot" where the wire insulation could break down. In the present day - the oil is gone and the modern insulation coverings are a plastic or epoxy intended to take the heat directly - no more oil. The quality (or lack there of) of modern replacement coils gets discussed here a lot!
(4) It takes a maximum of 10,000 volts to fire a spark plug in most all circumstances (usually less). Have a coil of 50,000 V rating? - It is the rating of the wire and enclosure insulation - and makes great advertising - but the plugs still fire at 10,000 volts or less.




 
 Steve Metzger       Tucson, Arizona

Thanks Steve. Good explanation.
A note to those guys recommending points. Remember Henry Ford started with cars that had MAGNITOS but we don`t use those anymore either. Why not? Pete

I should have said built in resistance, not resistor, sometimes something shorts out between my brain and the keyboard, my bad..

Greetings to all: I have thus far only been able to compare the two systems by running them on the distributor tester. I'll have to wait until spring to run the Ignitor 2 and the 40,000V coil in the real world. I chose the 40KV coil due to it's higher resistance of 1.5 ohms to hopefully not build up as much heat.  Reading the last several posts tends to throw water on this logic. Nat burned-up several 1.5 ohm coils and Charlie used the lower resistance coil and never had a problem.  This suggests the 40KV coil may not be up to the task if the resistor is eliminated making the Flame Thrower 2 coil the better choice?  As for leaving the key on and engine off, I did put an ammeter in the primary circuit and when the dist. machine stopped, the current dropped to zero with 12.5V still present.  Maybe Charliemaccraney had a defective Ignitor 2.   As stated in my first post, I was able to lean the idle mixture screws over 1/4 turn and the exhaust seemed to be more pleasant.  


64F100 57FAIRLANE500