Ignition: Ignition coil resistor

[Noxnabaker]

I'm wondering about the need for external resistor for the ignition coil... What's the reason for some coils with vs some without resistor?

[Jeffry Cassel]

The resistor allows for it to be bypassed for engine start-up so that 12v is delivered to the coil. When the starter is disengaged current flows to the resistor which drops voltage to the coil to about 6v. This is to avoid premature ignition point burn out. If you use a coil with an internal resistor you won't have the extra start -up voltage and may experience hard starting. These resistors are cheap and easy to find. Any Studebaker parts vendor should have them or you can go to RockAuto.com. Later models had an ignition resistor (pink) wire, but many are burned out now and they are impossible to locate. If you switch to Pertronix, they recommend a full12v to the coil, but then again some say the module will last longer at a lower voltage. If the pink wire burns out it can be replaced with a resistor. Always carry spare points, resistor , condensor, and rotor in the glove box!

[Noxnabaker]

Aha, that clear up a lot for me, thanx!
There's MoPar stuff in Josephine & no contact brakers but it's still good to know & understand & she's not my only car, even thou this was about her.

[Bud]

A 12 volt coil using an external resistor will run at 9 or 10 volts with the engine running. The resistor cuts down the voltage across the points to increase point life. The resistor which will usually run in the 1.5 ohms range or thereabout which drops the voltage across the points to an acceptable level. The resistor is by passed by the starter solenoid when the starter is engaged to allow for more voltage in the coil primary to ease in starting. Very rarely is an internal ballast resistor coil used on a V8 engine, but they are used on some 6 and 4 cylinder engines. I don't care what Pertronix says about using their coils without a ballast resistor as I have had their coils fail due to overheating with the full 14 volts or so on the coil when the engine is running. The use of a resistor will reduce the coil output by a few kilo volts, but very few Studebaker engines will have a performance decrease because of it. Bud

[jrlemke]

Not to hi-jack this post, but, can I use one of the hi voltage electronic ignition coils (50=60 K) with points? I would use a ballast resistor and 8mm wires. Would I need to regap the plugs and to what gap? Thanks. -Jim

[Noxnabaker]

I don't care if someone hi-jack this thread Jim, I even like it because it's interesting!

[Bud]

I don't recommend using a high output electronic ignition coil with a points type ignition system as the high output coils have a much lower primary winding resistance than a coil meant for a points type ignition. A typical coil with about 1.5 ohms primary winding resistance will draw about 3 amps of current across the points where a high output coil could have a resistance below 1 ohm which will draw maybe double the current causing the points to fail in short order. As far as plug gap with a high out put coil, try opening the gap about .005" and see what happens. Like I said in an earlier post, the vast majority of Studebaker engines will run well with a stock coil. Bud

[Noxnabaker]

So if the distributer doesn't have points one could go for a high performance coil without much troubles..?

[Bud]

Theoretically, a high performance coil could be used with an electronic ignition, but there are variables such as what distributor is used. Like I said earlier the vast majority of Studebaker engines do not need a high performance coil. Maybe an R series engine could use one, but to me that is even doubtful as any beer can style high performance coil on a good day according to my scope is good for at best 35 kilo volts and a good stock coil will do 30 to about 32 kv depending on the coil. Bud

[jpepper]

Running voltage at the coil with points should be 9.8 - 10.2 volts. a 1.5 ohm resistor should get you there with a running voltage of 14 volts.