Always check the advance mechanism....they are usually worn and rusty.
And check the vacuum advance. When I bought my 69 the PO had slapped in a well-used hei. Milage was horrible, so I checked the vacuum advance, it didn't work. Bought a complete upgrade kit with hotter coil and performance module, advance module, springs & weights, cap & rotor. I also found the weights rusted in place, so I had been runniing only 6* advance at speed. Got 9 mpg on a road trip before the upgrade. Now I'm running 42* total advance, and am getting 14 mpg on the highway.
As far as voltage to the hei, they were designed to run anywhere from 11 to 15 volts. I don't know what the output voltage change is within that range, but if your module burnt out it was either a bad module, the voltage regulator was set way to high, dielectric grease hadn't been used or a static field had been introduced to the module. It wouldn't have been the fault of standard voltage. I'm not saying that the module won't last longer on the reduced voltage, it probably will. But it does raise another issue, what will happen if the alternator dies and the voltage at the hei drops to 8 volts? Will the hei have enough spark to run the engine? How about running a test on that, Richard? I'd like to know the results. Also, have you connected a voltmeter to the hei output and compared the voltage differences? This, too, would be interesting to see.
