[Nick_R_23]

No worries! Since you’re running stock, I’d gap at .035. I think you’ll find that’s optimum for what you’re doing.

The gap doesn’t determine how much voltage is command - but it does determine the amount of voltage required to force the spark to jump a given distance, which may exceed your coil’s capability. There are actual numbers that I don’t know off the top of my head, but for ease of explanation, let’s say that every .010” of plug gap requires 10,000v to reliably jump the gap and create a good spark. .020” requires 20,000v, .030”, requires 30,000v, and so on. Let’s say the coil is stock, capable of producing 40,000v. You coil would be safe until .040”. Now, let’s say you want a .060” plug gap - your coil may not be up to the task. Spark plug air gap should be thought of as a measure of resistance - you aren’t providing the electricity with a direct path. You’re forcing it to travel over both a distance with no true conductor, and through air which is a resistor by itself. Picture a simple circuit with a battery and a light bulb, the bulb is bright until you add a resistor in line. Now add a larger resistor (larger gap), and the energy has an even more difficult time making it through, and the bulb is even dimmer. Too large of a resistor and the bulb will not light at all. At this point, we can either enlarge the energy source to overcome the resistor (larger coil) or remove some resistance to work with the energy source in place (smaller gap). Of course, this assumes your wires are rated to carry the given load, which is why wires too small in a normal circuit, or worn, high resistance spark plug wires will cause problems. They’re subtracting from what your energy source (coil) is capable of outputting.

The coil can only put out what it’s capable of producing - which is partially determined by the internal structure of the coil, and partially from the quality of voltage seen at the input (13.8+ volts, vs a weak - for example, only 11.8v - or shared voltage line, which is why it’s recommended not to share coil voltage with other components), and also from coil saturation, the time the coil is allowed to build a charge internally. Your dwell, or time the coil is given to build this energy, can have a negative effect on coil output if the time given is too short. This is why MSD boxes have diminishing effects approaching 3000 rpm. The coil will always put out it’s rated voltage, assuming the source voltage and saturation time are proper. Your spark plug gapped at .030” may not require that full voltage, but it will still see that full voltage regardless. Your spark plug gapped at .060” may require that full voltage, and then some, but it will not see more voltage than the coil can produce. In this case, a better coil would be a good investment, not to gain power, but to prevent a loss. Whether the .060” gap is necessary, will depend on the engine, components, and intended usage. Usually, it will not be.