sevntyW30auto

Is this a dealer sold item or just an 70's or 80's early version of an MSD box?

joe_padavano

Neither, actually. In the 70s there were a lot of aftermarket CDI systems like this. The advantage of CDI over a conventional coil is that the capacitor charges and discharges much more quickly than the coil, allowing the CDI system to provide reliable spark at engine speeds up to 10,000 RPM. The value of using a system like this on a street motor that almost never goes over 5 grand is questionable. Of course, that logic didn't prevent us from installing these on our cars then, since the butt dyno said they were an improvement.

Yes, the MSD is also a CDI system, but the key difference with the MSD is the multiple spark (as in Multiple Spark Discharge). The MSD takes advantage of this quick charge/discharge capability to fire the spark multiple times on every compression stroke. A conventional system can't do that.

joe_padavano

Here's an ad for the Compu-Spark from 1974. They were made by *******.