With the ignition switch on, AND THE POINTS CLOSED, the voltage at the + terminal of the coil should read about 9.5 VDC. The only time you'll see a voltage reduction is while current is flowing through the points. If the points are open, you'll see 12 volts at the coil because no current is flowing. The bypass lead from the starter solenoid to the coil provides full battery voltage while the starter is cranking, which is lower because of the load on the starter. The coil primary is actually wound to operate properly at 9.5 volts or so. If you bypass the resistor the points will burn quickly from too much current flow. The "no resistor required" coil will probably give you a weak spark during cranking because of inadequate current flow while the battery voltage is decreased from powering the starter.
Jerry
