by Robert S. Hoover

Point Settings Explained

If the gap is too small the coil's magnetic field will not be fully collapsed before it begins to re-charge. The net effect is to reduce your spark voltage and duration. At anything above an idle this results in very doggy performance.

If the small point-gap was the result of rubbing block wear a check of your timing would have shown it to be retarded by several degrees.

Oddly enough, setting your points either too wide OR too close... and then timing the engine to that firing point, has about the same effect, which is to limit performance to a relatively low rpm.

As a point of interest, you would not have noticed this problem with a CDI module. It requires only the initial triggering -- dwell is not a factor. Timing does change as the rubbing block wears (assuming you use the stock points for the triggering signal) but it's a simple matter to check this periodically and tweak the timing. It takes about fifty thousand miles for the rubbing block to wear-down to where the point will not open at all, assuming you start with a point-gap of .020", proper lubricant and so forth, at which point you may be able to simple re-set the gap (I got 138,000 miles from a set of points on my Datsun). Once the CDI module gets the firing signal, it fires full-voltage every time. Unlike your stock ignition system, a CDI module pays no attention to when the points CLOSE, only to when they OPEN, and that opening can only a thousandth of an inch and still get the job done.

As part of the LPG conversion I'm investigating magnetic ignition triggering. I'm running a Pertronix 'Ignitor' on the bus and have another undergoing non-destructive testing. Pertronix offers only a 30 month warranty and I'd like to know why. The standard Hall Effect trigger should justify a longer warranty. (I'll be posting a report on this shortly.)

If you are considering replacing your points with some other form of ignition trigger I think it would be wise to AVOID optically triggered systems. Detroit -- and everyone else -- went to magnetic triggers for good reason.

-Bob Hoover

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