Can my coil be damaged?

I have been tinkering with my 65 Ford Mustang six ignition. With an ACCEL coil rated at 1.4 ohms and a .8 ohms ignition resistor, will I damage the coil? After driving about 30 miles I checked the coil for overheating and it seemed normal (basic engine heat) and the car ran fine. I run a Pertronix in the dizzy with 8.8 mm wire wound resistance wires feeding Autolite platinum plugs gapped at .038. Timing is 12 degrees with vacuum shut off and dwell is 38 degrees.
I have stated here before I run a points distributor in my 200 Ford six but usually with a Pertronix conversion. After finding a later 200 head (1973) I plan to have it machined for a direct fit 2-barrel carb. Now I am using a 2-barrel adaptor and I want as much spark as possible at the plugs without hurting the basic Kettering system. I understand ignitions fairly well but at 75 and after a stroke a few years back, I sometimes doubt my thinking. The wife of 53 years makes remarks about my thinking before the stroke and believes I have not changed one bit! Anyway, going from a 1.4 ohm to a less resistance .8 ohm resistor (little more primary volts to coil) am I asking for trouble? We travel fairly long distances in the Mustang and I keep a coil, points, cond., in the glovebox...just in case. Should I keep a 1.4 ohms resistor also? The coil having a 100 to 1 ratio and the plugs set at .038 or maybe .040" am I okay? It works on short trips around town but we plan long trips and that is my concern. This is the engine and the LH-6 stands for Long Haul 6-Cylinder. THANKS ahead.


Ranger Mike

Science Advisor
Gold Member
Being an old Mopar guy I am often asked about Mopar ignition systems and whether or not the ballast resistor is a necessary item. All cars produced with breaker-points type ignition generally had a resistor of some sort in their ignition system. Some brands utilized a resistor in the coil or a resistor wire hidden in the wiring from the ignition switch, but Mopar put their resistor (or ballast resistor) on the firewall. The ballast resistor in a Mopar limits the amperage, or current flow, through the coil while the engine is running, thereby extending the life of the coil and breaker points of the distributor. When the ignition key is in the start position, full current is applied to the coil and increases voltage to the spark plugs. In fact you are shooting 14 Volts to the coil at start up and if you do not have the resistor you will fry t he points a lot quicker.

Chryslers electronic ignition systems used a dual ballast resistor, again to extend coil life and provide a constant primary current. Again the system also bypassed the resistor to apply full amperage to the coil during startup. In either type of ignition system, points or electronic, the ballast resistor can be removed to increase secondary voltage to the spark plugs, but the long-term effects of removing the resistor differ between the two systems.

An ignition system with breaker points will suffer from reduced point life if the ballast resistor is removed, as higher amperage can damage the surface of the points causing failure. Additionally, if the ignition is left in the run position and the points happen to be open-or worse, barely open-electrical arcs can cause raised spots on the points resulting in a change in dwell timing or an engine that won’t run at all.

Electronic ignition systems, whether factory Mopar or aftermarket, don’t utilize breaker points, thereby not actually needing a ballast resistor to control amperage through the pickup coil. And while ignition coil life may be compromised without a resistor, the additional secondary voltage (at the spark plug) is increased which generally improves power. So does your application require a ballast resistor? Quite simply, if your distributor has breaker points the answer is yes; if not, the answer is no. Run the lower amp resistor and you will be fine.

Trivia fact. EDM machines or Electrical Discharge Machine was invented by a couple of Russians that sealed up a distributor cap and filled it with oil to increase the points life. It did just the opposite and thus the EDM machine was born.
Ranger Mike, thanks for the input. My Dad was also a MOPAR fan and his 55 Dodge Coronet with Red Ram V8 had dual points, so I learned about points function at an early age. For several years I had a 98 Ram pickup and liked it. I guess my concern is the lower resistance in the primary possibly hurting the coil or points. My Fluke reads just under 11 volts while running. The points condenser is the best I can find, so easing damage to the points is maybe okay...but my stroke seems to have left a blank spot in some of my electronics memory. More volts in the primary equals more output, but with a small backwash of voltage (my term) in the primary, might hurt the points with an arch...thus the reason for best condenser. With 2.83 rear gears, 26.3" tall tires, and a 2-barrel carb, my Mustang will probably never see 5,500 RPM, so hi-revving is not my goal, but dependability is, with a clean running engine. Thanks again for easing my mind about my modified old points ignition.

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