Electronic Ignition Systems for the Z Magnette

Details

Written by Malcolm Eades

Many classic car owners have gone down the road of fitting a good quality contactless ignition system. They overcome the Achilles' heel of the contact breaker and require no adjustment. The solid-state electronics also enhance the quality of the spark.

With miniaturisation, it is now possible to fit a system that sits inside the distributor in place of the points. This is undoubtedly the best solution if you want to preserve original appearance. The only give-away is the fact that two wires exit the distributor instead of one. Other designs are supplied with a small control box that can be mounted unobtrusively and those that are brightly coloured can be overpainted or disguised with a dummy cover. Mount these preferably in a cool location.

If you are using your original distributor with one of the electronic switching systems, it needs to be in tip-top condition. No amount of electronics will make up for a worn spindle or slack bob-weight springs. Be careful about polarity too. Be sure to get a unit that is right for your car. If you are going as far as fitting an electronic ignition you may well conclude that it is time to change to negative earth polarity too.

Systems that are known to work with the B-series engine include:

123 Distributor - This is a complete replacement distributor that uses electronics rather than centrifugal force to generate the advance curve and a choice of 16 curves is available in each unit, selectable with a simple switch. Vacuum and non-vacuum units are available. Details here

Pertronix Ignitor  or Ignitor 2 - The sensor head replaces the points and sits entirely within the standard distributor with no external components except the two wires that emerge from the usual low tension connection point. American manufacturer but widely available from performance component suppliers. A matching Flame-thrower coil is also available. Details here

Aldon Ignitor - This unit is similar in all respects to the Pertronix. Aldon Automotive is a UK tuning and performance specialist that will also work on cars and use a dynamometer to achieve maximum results. Details here

Lumenition - Although originally known for its "optronic" unit that uses an optical interruptor instead of points and  has a separate control box in the engine bay, Lumnitition now also offer a "magnetronic" unit similar to the Pertronix. It, too, fits entirely under the distributor cap. Details here

Piranha  - This unit also uses a control box. Although you may see it still available, it appears to have been bought out by Newtronic who also make Lumenition, so future availability is unclear.

The higher output capabilities of electronic systems make it possible and, indeed, desirable to fit a high performance coil. The manufacturer of the system will generally offer their own unit or recommend one. It also becomes possible to open the spark plug gap because the fatter spark will cope with the larger gap. 0.035" is a good compromise because a much larger gap will also increase the rate of erosion at the plug tip.

I have been running a Magnette and an MGA with electronic systems for some time now and can confirm that they enhance starting, make for a smoother, stronger tick-over and increase engine performance. However, one word of warning. Solid state electronics usually work trouble-free for a long time but on the day that yours fails, you don't want to be stuck on the roadside, unable to do anything about it especially a long way from home. If you use a replacement distributor, keep the old one, in good working order, in the boot. If you use the system that fits instead of the points, keep a set of points, a capacitor and the associated wiring in the boot. These give you the get-you-home fix.

Post script January 2013:

Since writing the above article, I have encountered some problems with the electronic ignition fitted to my MGA. However, this had nothing to do with a malfunction of the unit itself. When I removed my distributor and stripped it down, I found that over time the advance/retard movement of the baseplate had worn a tiny bare patch on one of the wires connecting to the sensor head. This was allowing an intermittent short circuit. This emphasises how much care is needed when assembling the unit into the distributor body.