Ignition Resistor

[Milt K from Pa]

Its really a interpetation issue i guess.

The primary circuit of a coil is a resistor ( or maybe i should say it has resistance in it to please everyone).
Each oem has always offered a primary coil resistance specification so the mechanic could check the coils internal resitance.
So lets use a specific system with a 6 volt battery on a 1940 Ford, the oem coil has a resistance of approx 1.5 ohms and the under dash resistor is also approx 1.5 ohms ( rounding them off for explamation sake.).
The total resistance is 3.0 ohms and 3.0 divided into 6 volts would give the system ( under good conditions) a current flow of 2 ampheres.
This would be the expected current flow of a orginal 1940 ford with 6 volts.
The system is designed to use a coil with ressitance and a seperate resistor.
Now somewhere in the years a manufacture used a coil with a "internal" resistor of 3.0 ohms total and this coil woild not need the seperate ballast resistor ( like some of the 53 Fords etc)
This was often refered to ( and labeled on the coil) as a internally resisted coil.

Now if the customer used this coil WITH the ballast resitor the total resistance would be 1.5 plus the coils 3 for a total of 4.5 ohms.
4.5 ohms divided into the 6 volts would equal = 1.3 ampheres which would give a very weak spark.

Each piece of each ignition needs to be correct for the application.

I had this very car in my shop this week. Complaint was hard to start and poor running.
The fix was to check the coils resistance, check that is was in fact a internally resisted coil, and bypass the resitor. ( no longer needed)

Couple this with a bolt on battery terminal ( a volt drop) and the spark was very weak at best.......

Bubba,
A bit of a hole in your description of current flow in the above exercise. With 3 ohms resistence in the coil and the resistor, current flow would be "one" ampere, not two. As far as most hands on folks say, 3 volts at the coil is probably too low and would cause hard starting, considering the voltage would be lower during starting.
Milt K from Pa

 

[Rowdy]

Pic's of parts pu. Price was right for whatwas there. Rod

 

[BUBBAS IGNITION]

Bubba,
A bit of a hole in your description of current flow in the above exercise. With 3 ohms resistence in the coil and the resistor, current flow would be "one" ampere, not two. As far as most hands on folks say, 3 volts at the coil is probably too low and would cause hard starting, considering the voltage would be lower during starting.
Milt K from Pa

1.5 in the resistor and 1.5 in the coil ( pretty common set up) would total the primary resistance at 3 ohms.
Three ohms divided into 6 volts ( battery) would equal (here in Indiana) a current flow of 2 amps?????
Did i say that wrong?

 

[George/Maine]

Of all the 6 volt coils Ford is the only one that needs a resister,years 1932 1948.One book say .5 ohms, Echlin ICR 40 says .35 so 6 volts systems,would have +or -using 3 amps as a example. 3x.35 =1.05 volts,.5x3=1.5 volts.The rest of the voltage is to coil.With 4 resisters to pick from buy a mulite meter and check them out,using the ohms scale,as for the starter just run a wire direct to starter.

 

[aaron griffey]

I have know several Fords from '32 to '48 that were driven many miles with the restor bypassed.
The 4 cylinder Ford coils worked without a resistor, all v8's had them.
For permanent installations get a Blue Streak 6 volt coil or a '66 and older VW coil. They do not need restistors.
The Blue Streak may have to bee ordered, they are a little more expensive but they will give good spark when the car is hot and cranking slowly. They are a higher out-put coil.'I have installed maybe 6 on a Ford collector's cars with Excellent results.
The end-all way is to have stock coils rebuilt by Skip.