Slant 6 Dual Point Distributor Conversion.

Rob they both have to be open at some time to build up the dwell time. Good example is a stock DP. Both set at 30 degree dwell and when they are read combined usually about 42 dwell. If one closes completely it stops the added dwell and would read 30 ish. Hope that made sense.

Stole this
With two contact sets mechanically offset by 9 degrees, the closed period for the two sets overlaps by 23 degrees but extends the total dwell angle from 32 degrees to 41 degrees. ... When the 8-cylinder Mallory Dual Points makes 33 degrees dwell it is down to only 12 degrees open. You might see where this trend is going.


The points act at nearly but not exactly the same time. There is overlap or a "handoff", meaning that the contact made between the power supply and the coil stays longer, leading to a higher saturation or "charge" in the coil, leading to a higher voltage spark. (by the way, there's no such thing as a "longer" spark, if "longer" means time, but a higher voltage spark can travel a longer distance over a bigger gap).

Think of it like this, you have Points A and Points B, as the cam turns, Points A reach the low spot first (they Close) and get charged while on the low spot. B follows and continues the circuit. Turn more and Points A reach the high spot and open, but B isn't there yet so the circuit is still closed. When B reaches the high spot the circuit is opened and the coil fires.