Can this cause a misfiring engine?

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   If the 58 uses a ballast resistor, just wire it on the switched power end of the resistor -- the end with the wire from the wiring harness, not the end going to the distributor. Don't eliminate or bypass the ballast resistor unless you're replacing the coil with one that has a built-in ballast. The ballast resistor allows a full 12V to pass through it when it's cold, and increases resistance to drop voltage to 9V when it's hot. This maintains current (amps) to the coil by varying voltage to the coil. So it gets more voltage at low temps to create a higher amperage for starting, but the voltage is decreased as it warms up (due to the amount of current -- amps -- flowing through it) to keep the amperage at the coil the same as the spark needs less current to be maintained after the engine is running. That's a simple explanation, I'm sure there is technically more to it than that! Ballast resistors were later replaced by resistance wire in the late 60s. (68 or so). I hate resistance wires! They are buried in the wire harness and they do wear out. Okay, it takes 20+ years, but that means a lot of late 60s and 70s cars have worn out resistance wires. Most just bypass the original ignition wire with a new one rather than cut the harness open and dig the old one out and replace. It could be replaced with a resistance wire or coil with built-in ballast. That's why you have to be careful when replacing the coil. Using one with a built-in ballast along with a ballast resistor or resistance wire will result in insufficient current to the coil shortly after start-up and obviously weak spark issues.

"A resistor that has the property to increase the resistance when the flow of current through it increases & decreases resistance when current flow decreases are called a ballast resistor.
 This resistor maintains a stable current flow through it, even though 
differences within applied voltage or within the rest of the circuit. 
The ballast action can be obtained through resistive material that 
increases resistance when temperature increases."

Edited by farna - May/12/2023 at 7:03am

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farna Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19679	Post Options Post Reply Quote farna Report Post Thanks(0) Quote Reply Posted: May/12/2023 at 6:57am
	If the 58 uses a ballast resistor, just wire it on the switched power end of the resistor -- the end with the wire from the wiring harness, not the end going to the distributor. Don't eliminate or bypass the ballast resistor unless you're replacing the coil with one that has a built-in ballast. The ballast resistor allows a full 12V to pass through it when it's cold, and increases resistance to drop voltage to 9V when it's hot. This maintains current (amps) to the coil by varying voltage to the coil. So it gets more voltage at low temps to create a higher amperage for starting, but the voltage is decreased as it warms up (due to the amount of current -- amps -- flowing through it) to keep the amperage at the coil the same as the spark needs less current to be maintained after the engine is running. That's a simple explanation, I'm sure there is technically more to it than that! Ballast resistors were later replaced by resistance wire in the late 60s. (68 or so). I hate resistance wires! They are buried in the wire harness and they do wear out. Okay, it takes 20+ years, but that means a lot of late 60s and 70s cars have worn out resistance wires. Most just bypass the original ignition wire with a new one rather than cut the harness open and dig the old one out and replace. It could be replaced with a resistance wire or coil with built-in ballast. That's why you have to be careful when replacing the coil. Using one with a built-in ballast along with a ballast resistor or resistance wire will result in insufficient current to the coil shortly after start-up and obviously weak spark issues. "A resistor that has the property to increase the resistance when the flow of current through it increases & decreases resistance when current flow decreases are called a ballast resistor. This resistor maintains a stable current flow through it, even though differences within applied voltage or within the rest of the circuit. The ballast action can be obtained through resistive material that increases resistance when temperature increases." Edited by farna - May/12/2023 at 7:03am
	Frank Swygert

wittsend Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Apr/15/2020 Location: California Status: Offline Points: 427	Post Options Post Reply Quote wittsend Report Post Thanks(0) Quote Reply Posted: May/12/2023 at 11:49am
	To add to the above coils can be wound to work on any voltage though automotive they are typically 6 or 12 volts. And in reality they are designed to operate on less voltage than their stated voltage. Meaning a 12 volt coil typically operates on about 9 volts. The whole purpose is to allow for a momentary stronger spark at 12 volts when the engine is cranking for assist in getting the engine to start but a lesser voltage once it is running to sustain the life of the coil. So..., when using a Pertronix it has to be seen as two sperate systems. The coil (assuming using the stock one) must maintain its resistor or resistor wire. Remember the resistor always relates to the coil. The Pertronix works on 12 volts. It is rate at 9-12 volts but I have seen a lot of people have issues on the lesser voltage. So, it needs a dedicated 12 volt source. That is why I like a dedicated wire from the ignition switch. Lastly remember the voltage to the coil on the + side is constant. The points (or Pertronix like devices) make and break ground on the - side of the coil. That is what triggers the spark. A lot of people assume because the Pertronix has a red wire that it feeds 12 volts + to the coil but that is not the case. The Pertronix simply grounds the coil just like points do. It however does it electronically rather than mechanically with moving points. Simple rules for a Pertronix: - Run an ignition switched 12 volts + to the red wire on the Pertronix. - Run the ballast resistor or resistance wire appropriate for the coil used. Edited by wittsend - May/12/2023 at 11:59am
	'63 American Hardtop

farna Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19679	Post Options Post Reply Quote farna Report Post Thanks(0) Quote Reply Posted: May/12/2023 at 6:55pm
	The older original Pertronix (Ignitor... doesn't have a "1" in the name, but some call it "Ignitor 1") works just fine on 9-12V. The Ignitor II and Ignitor III pretty much require 12V. I don't know what the specs say for the II, but the III definitely needs 12V. Ignitor is as simple drop in points replacement ignition. Provides a more accurate trigger signal. Ignitor II adds increased starting voltage and adaptive dwell. Ignitor III adds a digital rev limiter. Preset to 5000 rpm, it can be user set 4000-9000 rpm. There may not be a III for all applications.
	Frank Swygert