Hudson Dual Point Distributor

Hudson308 wrote:

Dual-point distributors were also standard equipment for early Hemi automotive V8's. The "stepped" point action allowed a bit more dwell/coil saturation, which could give you a hotter spark at higher RPM's. The two point sets are connected in parallel, and are situated so that set number 1 closes slightly ahead of number 2, then number 2 opens slighty behind number 1. This arrangement will still function if one set were to stay open (or be removed) for some reason, although timing and dwell will be off a bit. There is no advantage to this system at lower RPM's.

There is another reason for aftermarket dual point distributors back in the day.



It was to allow the most timing advance possible without the engine pinging in higher gears.



It worked like this:



The first set of points was in use on the first 3 gears, (using a 4 speed standard shift car as an example). That set of points was adjusted advanced enough to not ping in the first three gears, but to ping in fourth. Remember that the two points could be adjusted to open and close at different advance/retard times.



When the car was shifted into fourth gear, an electrical switch on the shift likage disconnected the first set of points, and simultaneously connected the second set of points.



The second set was adjusted so it was in a slightly retarded timing position compared to the first set. Thus the car could have maximum timing advance in the lower gears for the most power, but less in the top gear where it is more likely to ping.



This is because the taller the gear, the less mechanical advantage the engine has, and the more apt it is to ping.



From working in a speed shop back in the 60's, most of the sales were to 1/4 mile drag racers and short circle track racers who used it for the purpose mentioned, rather than getting a hotter spark with one advance curve.