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The ignition is separated by primary and secondary parts. The primary ignition is the low voltage side; points, condenser, etc. The secondary ignition is the high voltage side; coil, cap, rotor, wires, and plugs. The primary side of the ignition is responsible for the triggering of the spark, and the secondary side is responsible for the spark.

Primary Ignition

In some opinion, points are obsolete. Unless you like messing around with them, replace them with some sort of magnetic triggering device (Compufire, Pertronix, etc). These do not increase your spark quality (like some claim) compared to a properly operating points triggered ignition. However, they do not deteriorate like conventional points/condenser ignitions. They are exceptionally reliable, and they will be rock steady at all RPMs, which can not be said for points. Basically, the magnetic pickup assures optimum triggering all the time. Simply buy the magnetic pickup points replacement unit and throw the points in the glove box in case you have a problem with the magnetic unit. The MSD distributor comes with the magnetic pickup as part of the distributor, so you don't have to worry about it on that model.

Secondary Ignition

This is another place where large improvements in engine operation can be gained. Frankly, the stock Bosch coil is only adequate to about 2500RPMs, and the spark quality deteriorates from this point and up. The problem is with the coil's primary voltage (12-14V). As engine RPMs increase, there is less time for the primary voltage at the coil to create the required magnetic field that generates the high voltage spark we need at the plugs. There are two solutions: 1) increase coil current. The problem with this is that you will burn out points (if equipped) much faster, since the coil's current is passing through the points. 2) increase the coil's primary voltage. This is the solution that Jacob's, Universal, MSD, and other companies have decided to use. There is no drawback to this solution other than cost.

Once the secondary ignition is improved with a CDI or Jacobs, the spark plug gap can be increased to 0.040-0.045'. Be aware that you may have to re-set your timing, since the larger plug gap and better spark can speed up the time the flame front reaches the piston (detonation). You will find smooth running at all temperatures and INSTANT starting (not like before), with a 10-15% increase in mileage. This savings in fuel will pay for the CDI quickly!

High Output Engines

Another issue that you must be aware of is that high output ignitions MAY have a problem with the small diameter distributor caps on the Bosch units. There is a reason the MSD and Mallory distributors have a large cap, and that is to minimize the possibility of the spark jumping to a contact that it is not intended for! Another problem is that the Bosch rotor has a resistor in it, which will burn out in a short period of time if used with a high output ignition. You can dig it out, and solder a solid piece of brass in its place (it's between the tip and the cap contact area).


engine, ignition, distributor