To get an added kick that is missing from your stock ignition system (or most after market conversions such as Crane or Pertronix systems), MSD makes several capacitive discharge multi-spark ignition systems. I recently added the MSD 6AL to my Race Spit and I am very pleased with the results. I chose the 6AL because it includes a built-in Rev Limiter that is programmable by exchanging plug-in modules. Below are some of the things that might cause installation problems.
1. There is a pair of jumper wires hidden under a cover on the side of the unit for setting the engine configuration. Both wires must be cut for a 4 cylinder.
2. When using the unit with a Pertronix Ignitor system, you would think that you would use the two wires provided for connection to magnetic pickups (since this is what the Pertronix is). You would be wrong. According to MSD's Tech Department, the Pertronix is treated just like points and is connected accordingly.
3. Spitfires will continue to run after the ignition is shutoff if a diode (provided in the kit) is not installed in the wire that goes from the alternator to the charge lamp on the dash. This is because the small amount of current provided in that circuit is sufficient to keep the MSD unit running. The diode shuts it off when the ignition switch is turned off.
4. There is a special plug for connecting the trigger for most electronic tachometers.
5. These units cannot be used with solid spark plug wires. They require spiral-wound magnetic suppression wires (also referred to as Heli-core wires) to prevent erratic operation due to RF interference generated by solid wires. I found that Borg-Warner sells these wires specifically for Spitfires under their part number CH7419. They are around $10 to $15 (US).
6. The plugs must be re-gapped to .050-.060 (up to 10.5:1 compression), .040-.050 (10.5 to 13:1 compression) or .035-.045 (over 13:1 compression) Some experimentation may be required to set the gap for the optimum performance.
7. The installation instructions are very straight forward and noting the above items should be accomplished with little effort or setbacks.