[bigblockv6]

It's possible that you're using the wrong module in Your HEI or the wrong coil. The Chevrolet HEI uses the coil with red and yellow wires while the Buick,Olds, Pontiac & Cadillac versions uses the coil with red and white wire, you have to use the corresponding module with it. I found this out some 22 years when I decided to use a fancy Chevrolet application Accel Super Coil in the Buick HEI on my 68 pickup, well within a month or so it burn up the module so I went back to the correct coil and the problem was solved.