you guys are saying if plug is gapped at 39 instead of 43 the coils aren't working as hard. ??? Once the coil fires and its on its way to plug what tells it the gap ???
Bear with me here. An excellent question, but the answer can take a moment or two to explain.
Electricity is the movement of Electrons from one Atom to another in a directed fashion. Since everything is made of Atoms; everything is a potential Conductor, and at the very same time, everything is a potential Insulator. Whether we call something an Insulator or a Conductor has to do with how hard the Electrons are being pushed from one Atom to another. If you don't push the Electrons at all? Everything is an Insulator. On the other hand, if you push hard enough, everything will become a Conductor at some point. How hard you push is called "Voltage". How fast the electrons move (if at all) is called "Amperes". How hard it is to move the Electrons is called "Resistance". Conversely one way of describing how easy it is to move the Electrons can be called the materials "Dielectric Strength".
So, for example: Copper is considered a very good Conductor because it takes very little effort (Voltage) to push Electrons from one Atom of Copper, to another Atom of Copper. In fact Copper (not Gold) is the best Conductor there is. Gold is #3 but Gold has other properties that can make it highly desirable for use in electrical circuits. But I digress . . . On the other hand, Air (Oxygen 22% and Nitrogen 77%) is considered a fairly good Insulator, because it is relatively difficult to push an Electron from one Atom of Oxygen or Nitrogen to another Atom of Nitrogen or Oxygen. In fact it takes about 50,000 Volts to move an Electron through one inch of Air. Thus we say that the Dielectric Strength of Air is 50,000 Volts per Inch.
The challenge of a Spark Plug Gap, during the compression stroke of an engine, is that it is comprised of Air and Fuel as well as stuff left over from the previous Power Stroke, plus any Oil coming past the Piston Rings, plus etc., etc. When an Ignition Coil fires it does so because a Magnetic Field Collapses around the Coil which raises the Voltage of the Coil (this is very over simplified BTW). But as the Voltage of the Coil rises there is a very good Insulator in the Circuit. The Spark Plug Gap and all the "stuff" that is between that Spark Plug Gap . . . none of which is a particularly good Conductor. So as the Magnetic Field is collapsing and causing the Coil Voltage to rise . . . there is no current in the Circuit because of that Insulator called the Spark Plug Gap. But let's remember . . . if you push hard enough (raise the Voltage high enough) you can turn anything into a Conductor. So, if the Ignition Coil Voltage rises high enough to turn all the stuff that is in the Spark Plug Gap into a Conductor . . . a "Spark" (Amperage) jumps between the Center Electrode and the Side Electrode of the Spark Plug and BANG the mixture gets ignited. All is Good!
However, if the Voltage needed to bridge the Spark Plug gap becomes to high . . . it may actually become higher than the Voltage needed to turn other parts of the Ignition System, such as the Spark Plug Wire Insulation, the Plastic Housing of the Ignition Coil or even the electrical circuits (like the computer) that control the Ignition Coil into a Conductor. This would NOT be good! Remember, if you push hard enough (voltage high enough) everything, sooner or later, will become a conductor. The trick is to design and manufacture a system that can raise the Voltage High enough to turn the Spark Plug Gap into a Conductor, without turning anything else in the Ignition System into a Conductor first. The problem with large Spark Plug Gaps, is that large Spark Plug Gaps are better Insulators and have a higher Dielectric Strength than smaller Spark Plug Gaps. Larger Spark Plug Gaps raise the Voltage needed to turn the Spark Plug Gap into a Conductor. Allow the Spark Plug Gap to become wide enough and the Voltage needed to bridge that Spark Plug Gap can become more than the Voltage needed to turn other parts of the Ignition System into a Conductor . . . and then we have, at the least, a misfire, and at the worst: failed Ignition Coils, failed Spark Plug Wires, failed Ignition Modules, up to and including damaging the Computer that controls the Ignition Coil.
. . . and so the story ends . . . and everyone lived happily ever after!
:smile2: