Solid wire ignition

the only thing an ignition box needs to worry about is
1) Flow through the box to power the coil, when it is on, for the period it is on for. ( dicated by primary resistance and ballast or just primary resistance)

2) The back emf from the primary side of the coil at switch off. this is dictated by switching speed and coil ratio. (impedance,resistance as well). so if the coil is sensible, no problem there, most fling back 250-400 V at the box. The box has some kind of "clamp" an electronic circuit to limit and leak-off any excess. This back EMF is normally used to fire simple tacho.

Think of the back emf as like the recoil of a gun. the ignition box pulls the trigger and suffers the backlash for each spark. with points, the condenser took the hit and some sparking at the points as they opened further dealt with it.

original 1974 HEI had a zener diode and capacitor combination to limit back EMF to 350 V because the module would break down when 400V going the "wrong way" was applied back from the coil primary.

modern HEI just has a capacitor and can handle 400V
presume mopar and mopar style boxes had similar.
modern stuff can put up with greater back emf so the need for the clamping circuit is reduced

the box is divorced totally from the High power side of the system. the only link is magnetic field in the core of the coil.

the box may have some chip based electronics in it
BUT its in a metal, grounded enclosure. the chances of EM radiation wiping a chip or causing an issue are low. its not exactly a Faraday cage but it nods in the right direction.

ignition box is most likely to fail on the high current switching side.
either because the coil primary resistance is too low and therefore the current is too high
OR
its ability to control dwell at low rpm is compromised resulting in much the same problem too much current for too long with the car running at 800 rpm or left with ignition on and engine stalled. mag triggered ignitions in general guard against this "switched on" doing nothing problem.

OR

the Back emf from the primary was so high 400- 600V that is caused some kind of arc over in the box..

(This and bits of corrosion floating about is what used to cause the old MSD 6ALs to crap out. Replace the components near the burn mark, clean out all of the white aluminium furyness growing from the inside of the box, fix the fuse wire if burnt, and it will start to whistle and whine again.)

OR some kinda weird crap happens as a combination of voltage regulator failure and burnt out diodes in your alternator

an alternator driven with full battery voltage into the field instead of the usual 0-5 V will output some astronomical voltages if your engine can turn it..which i'm sure it can...


this sounds like bad luck and not a problem with your leads...

Poor grounding of box to chassis or motor to chassis makes anything that uses ground as a reference, do stuff it wasn't supposed to do.

Dave