The problem is the surge (saturation surge) when you first turn on the key to start it, Phil...not when the coil is replenished between cylinder firing. That first surge is slow and allows the coil to absorb a lot of current but replenishment timing is in terms of apx 2.5~4mS or less depending on your rpms and during that sequence the coil isn't using as much amperage. It can't, actually. There isn't enough time between the on/off pulses for the coil to saturate as it will on startup. Just like in the points system it (the coil) is going from 0 to whatever it can build rapidly. However the HEI module can draw at least 20 (or more) amps when the coil first switches on (when you start the engine) and that's what will ruin your ignition switch (if the distributor/coil is not on a relay). I have the Langdon mini-hei too, by the way. Depending on the coil used, draw at idle runs about 3 to 4 amps and this will decline as your rpms increase (due entirely to the reduction in time of the pulses). The startup surge is what will fry your 10 or 20 amp rated ignition switch. It may not do it right away, either. As I recall mine took a couple of weeks to croak.
