41 ford stock distributor ignition resistor questions

[Veeder]

I have two ignition resistors both in the .6-..8 ohm range.

With points open still getting approx. 6 volts on the coil.

I keep thinking and reading I should only have approx 4 vdc.

What am I missing I know this is simple. .....

[flatheadmurre]

With points open no current flows and you don´t get a voltage drop over the resistor so what you see is battery voltage.
Voltage over coil with engine running is what matters.

[Veeder]

I put a scope on the condenssor post and I get a 0 to 6volt peak square wave. Granted with the engine running the voltage may be a bit higher feeding the resistor due to the generator but the voltage across the points is 6 volts. Is this ok in your opinion? ?

[supereal]

The wave form shows a TMS (root mean square) reading when the engine is running. The correct resistor is wound with nichrome wire that changes resistance as the voltage increases in the system to prevent damage to the ignition points and coil. The ohm value of the resistor out of the circuit would be in the range you say. The voltage in the vehicle system varies as the generator speed follows the engine speed. The resistor is a somewhat crude, but effective, "voltage regulator" for the ignition system.

[Veeder]

Very helpful and makes total sense. We ford stock folks need a 6 volt positive grd solid state ignition system designed and sold. Have a great wkend÷!

I guess that would toss out the "window stock"

[flatheadmurre]

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System voltage aint changing enough to make any big difference.
The heat of the coil is following engine rpm and so does heat of the resistor raising it´s value keeping the coil from frying.
Another benefit is that you get a "hotstart" initial with the resistor having a low resistance cold.