It's the other way around. "Dwell time" is points closed time and that is when the coil saturates---with DC current. But it DOES have to be open long enough for the spark to happen. And open is when the spark happens Only way I'd know how to do that would be to put it on a scope with a working coil and "simulated" plug gaps and see what it looks like. Actually you likely only need one gap........just run the coil wire to a plug and "scope" that. You'd want to check it at simulated idle, and expected max RPM, bearing in mind that's half crank RPM so spinning the dist. 3K is likely all you need
