Ignition - Pertronix Ignitor issues 

I have been using the Ignitor ignition systems for some 8 years or so, as long as they have available in the UK, and have never found fault with them nor had any reliability issues. Until the beginning of this year… 
A new customer for this year, racing an MG Midget here in UK under a limited mods category, was doing splendidly for the first couple of races, then started experiencing a misfire. Initially it was believed to be a fuel starvation/vaporization issue. All fuel pipes were checked and re-routed where it was considered necessary. Those still considered in danger of getting too warm were heat shielded. The misfire persisted. On to the ignition system. All was checked, but then a loose alternator wire was found and blamed for the fault. It wasn't. Back to the ignition system then. 
Since the engine would run, it wasn't considered to be the Ignitor ignition, since we are advised that these things either work or they don't. The car isn't close to me, and therefore I couldn't be on hand to physically carry out checks myself, so it was down to advise by phone and e-mail. We ran the gambit of all the usual suspects - plugs, leads, dizzy cap, rotor arm, coil and so on. After some time I popped the question about coil temperature, the reply was that it was so hot you couldn't comfortably hold it - A-ha!! But this was the second new Lucas Gold Sports coil tried… hmm. But it, too, was getting excessively hot - so it must be the coil right? Since the engine would still run, but the coil got hot after a short time. As the electronic ignitions don't really require a high-power coil, it was suggested a bog-standard 12-volt coil was tried. And there I left it as Mini Meet east was beckoning, so off I went… 
…to discover another couple of folk having the same problem. One was cured pretty quickly - miraculously seemingly as nothing was changed except the rotor arm. The other person's problem, however, was a harder nut to crack. Despite changing everything from the plugs to the coil and everything in between, the misfire persisted. Not at all helped by an occasional loss of power to the coil once the 'start' position of the ignition key was released… So there was more than one issue to cure - but it didn't explain the persistent misfire and red-hot coil. The coil type and suitability was checked - no problem there (using a coil made for ballast-resisted systems will not work properly and will cause the symptoms experienced here). One other problem I'd known in the UK was a misfire caused by the rivets holding the Ignitor pick-up together had become loose - so these were replaced and the unit worked fine. So I checked this, but all was OK here. 
The decision was taken to re-fit the standard points set-up in an effort to go back to basics - still believing, as advised, that electronic ignitions either work or they don't - since something was causing the coil to over-heat and therefore produce an inadequate spark. The engine ran like a Swiss watch! No misfire. No over-heating coil. And no cut-out when releasing the ignition switch from the 'start' position - although this was still considered a second issue. So why? The coil over-heating is generally caused by insufficient dwell period between each spark or insufficient voltage 'damping' (like when a condenser breaks down). Over-charging or under-charging by the charging system can be an issue, too much charge will cook the coil, too little will not allow the electronic ignition to function properly - but these didn't show in testing the relevant circuits… so where was the problem? It had my brain buzzing, and a determination to seek the solution once I'd returned to the UK. 
I called Aldon Automotive since they were the original importers and distributors of the Pertronix Ignitor kits and asked them their opinion. Their input was thus… 
They confirmed the previous statement about the charging system - make sure it wasn't over or under charging. Make sure the coil is suitable - they suggested a standard oil-filled coil with 3-ohms resistance for road use and a resin-filled coil with 1.5-ohms resistance for race use (quoting Lucas numbers 40511 - possibly 40501 - for road use and 40111 for race use). Make sure there is a good and proper earth between the Ignitor pick-up and the block - so that includes no dirt/grease between the pick-up and base plate, no thread-lock compound on the pick-up to base plate screw, a good earth between the sliding plates where a vacuum advance is used, a proper fixing where a vacuum unit is removed to fix the two plates together, clean base plate to dizzy body screws, clean dizzy clamp to retaining bolts fixing, and clean retaining bolts to block fixings. Apparently these units are very sensitive to poor earthing. They say 99.9% of problems experienced by Ignitor users are down to one of the above - otherwise they are a very reliable unit. 
So if you are having problems with an Ignitor set-up, make sure all the aforementioned are checked before returning the kit for testing.