Hei Module Symptoms: Rough Idle, Pinging, Poor Performance, Stalling When one part of the HEI module fails, the engine has no spark and does not run.

Davis improved the ignition module (called a Dyna-Mod module), upping the coil saturated to 7,000 rpm on street applications, and 10,000 rpm with DUI's race coil.

The beauty of an HEI is that even stock, it applies much more spark energy than a points-type ignition. Generally, stock HEI modules are current-limited to about 4 amps.

One of the reasons HEI is able to deliver more spark is that, thanks to the electronic ignition-control module, it can safely operate at much higher current loads. On a points-style distributor ...