The ignition system on your 6 cylinder engine is given 360 degrees of distributor rotation in which to fire all 6 cylinders.
In other words......... 360 degrees of distributor rotation in which to saturate (charge) the ignition coil, and then to discharge the high voltage to each cylinder within two full crankshaft revolutions.
This means that for each of the 6 cylinders, the ignition system contact points are given a 60 degree angle to do this.
Of that 60 degree angle, a portion is dedicated to coil saturation (points closed).
This is the dwell angle.
The remaining portion (points breaking) is given to spark firing and coil cooling.
At 1,000 rpm, this occurs 3,000 times per every minute.
Engineers have determined what the dwell is to be (per engine) for best performance.
Also, with a dwell meter connected, you will be able to see whether or not the dwell angle remains constant as engine speed is increased.
A ratical or unstable dwell angle represents a worn distributor shaft, etc, and will cause performance problems.
Setting gap only, will not let you see if all is OK.
Like said..... setting point gap is an estimate only of correct dwell angle.
Roll the dice if you prefer.:rolleyes:
.