BLMC Special Tool – Point Gapping

As mentioned in my Cars post about the Marina, I found an old “Special Tool” the other day.

Old cars like the Marina run a Points, or Contact Breaker, ignition system. Long story short, when the Points are closed, the coil is charging. As the distributor rotates, so does the lobes on the shaft. These lobes act on the Points, opening them. When the Points open the magnetic field collapses and the voltage in the coil increases to a very high voltage. This voltage then goes out through the Rotor, through the Cap and into the leads, creating a spark in the relevant Spark Plug.

Points visible on RH side, in Closed position

The gap of the Points is adjustable and there is usually a set range for them to be adjusted to. If they open too far, or not enough the car will run badly under different situations.

In the case of the B-Series Marina the gap should be between 0.35mm and 0.41mm. I tried various different gaps and found that my Marina ran best at the higher end of that range, at about 0.40-0.41mm.

Back many years ago when I had the Marina I learnt something interesting. It was recommended to use a scrap of cardboard from the cover of a telephone book, as it was the perfect size for the gaps on the B-Series powered Marina. Sure enough, it was perfect for my car and quick to use.

So, here’s my BLMC Special Tool. *pen for scale