The pink/black wire is a resistor wire, when a current runs through a resistance it creates heat.
The stock ignition runs on 6-9 volts not 12 volts, does your new distributor and coil run on full 12 volts or a reduced voltage like the stock ignition. One would think there would be some type of instructions included with the parts you bought.
The pink and black wire that runs to the coil is a resistor wire that reduces the voltage from 12 volts to somewhere from 6 to 9 volts. The yellow wire running from the starter to the coil supplies 12 volts, but only when the starter is engaged, once the ignition switch is turned from start to run there is no voltage source at the yellow wire. The heavy purple wire runs to the starter and supplies 12 volts to activate the starter solenoid and thus supply 12 volts to the yellow wire. The purple wire only activates the solenoid it doesn't turn the starter, that power is supplied by the positive battery cable attached to the starter.
Having the yellow wire attached to the coil helps with starting by supplying battery voltage to the coil not the lower voltage of the pink/black wire. I would hook up the yellow wire. Maybe the pink/black wire just got hot during the start procedure?
Another question, when you ran your HEI did you power it with the pink/black wire or have a switched 12 volt source? HEIs do run on full 12 volts.
