Stu I think I see your point. The dwell time while the points are open is a very small percentage of the time between lobes, even on a stock engine. Off hand I would say that the points are closed more than 90% of the time. Which gives the coil more than enough time saturate at low rpm, making the full voltage available in the secondary. In the dual point systems the points are obviously wired in parallel and it appears that by timing the two sets of points to break with an over lap you could theoretically reduce the dwell time down to zero. If the primary circuit were energized for 99.99% of the time that would be about as close to the maximum time that you could give a coil to saturate before both points were open and the secondary collapsed.

Sorry Doug, but the first part of your logic doesn’t seem right to me. The primary circuit is completed when the points are closed and the field builds up during this period. When the points open the field collapses and induces a current flow in the secondary creating the high voltage.

I would however agree with you on the point of coil saturation time when it comes to a high rpm engine. I have no idea in what time period the coil would saturate, I’m sure, that figure would cover a pretty broad spectrum depending on what coil you were testing. It would be interesting to see dyno tests, I’m sure that Mallory did a lot of that back in the day, unfortunately it’s probably all been trashed by now.

I think what your saying is, that at 3,000 rpm with a 6.7:1 compression ratio there doesn’t seem to be any need for dual points nor can I, see any reason for an increase in performance from the inliners that we are generally talking about here. I also can’t see where the compression ratio would be a factor in the lower rpm range. Obviously you always want the hottest spark possible and coil design, rpm, and compression ratio would all be factors that become increasingly more relevant as the rpm increases.
And Pop, yep, logic also dictates to me, that it’s pretty much a useless add-on for a 1950, 216 or just about any inliner!
Thanks for the comments, keeps the old brain exercised.
Denny Graham
Sandwich, IL

Denny G
Sandwich, IL