Did you install the carbon pill that connects the distributor to the coil (or the yellow bronze pill if you are using high performance ignition parts that would prevent you from hearing a radio played in your car). There has to be some physical connection between the distributor button and the coil or else the energy will simply arc from the coil to the distributor button burning up your HEI cap.
I know from experience that these little pills will fall out taking the silicon rubber retainer with it, if roughly examined (such as passing it around to your friends in the garage saying look at my cool new part that will make a bazillion horsepower when I'm finished).
I used to use only the brass part in a whole bunch of earlier builds of my hot rods, but after a while I just tried the carbon one out to see how it worked, and I didn't observe any difference in spark voltage or amperage. The carbon doesn't last as long, but I have a bunch of them from not having used them in the past and since I never throw anything away they were all still sitting in my electrical small parts drawer.
The up side is I can now hear my NPR or BBC news broadcasts when cruising instead of a lot of static (I still get static because I don't use resister plugs and I use metal core wires instead of the suppression spark plug wires.