Help Junkyard coil for HEI distributor?

BillGrissom said

If true, then I would have damaged a lot of coils (but didn't). I usually ground the negative lead for >1 sec before releasing (thus getting a spark). If 24A flows, the primary coil dissipates 288 W of heat (assuming a full 12 V on coil+). This will overheat it, but it takes minutes. For comparison, a hair dryer is ~1000 W.

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The ability of an epoxy potted coil to expel heat is not very good. Normal current is about 5A, Watts increases as current squared. At 5A, 12.5W, at 24A 288W, about 23x. In my ignitions I shut off power to coil in 0.2s for loss of trigger pulses, with good reason. It just takes burned enamel on a single winding turn to create a fault. There is no magic oil healing, like in can coil. It will take less than a second to reach 24A, if the plug is not connected, the flash over internal to the coil will render the coil limited from original capability. It can also be a lethal shock, at primary or secondary.