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When you go buy your plugs from the local advance crap ask for the gap size(on anything) and the gapper.....the rest is obvious.
There is some that is pre-gapped and cannot be gapped further
Ideal spark gap is sort of trial and error.
The bigger the gap, the larger the spark kernel which the old theory holds would be better for complete ignition. IF, and it is a very big IF the coil can fully Ionize the gap. If it can't then you end up with a weak spark or no spark at all. A smaller, fully ionized spark is better than a larger but weak spark. Too large a gap results in excess time required to ionize the gap, which is a loss of ignition timing advance. Coupled with the weaker spark kernel and you get less than stock performance.
The thing to remember is that the cylinder's pressure is quite a bit higher than ambient pressure (it had better be anyway!!) and that makes ionizing the gap much harder to do. Those old parts house counter top displays showing how much better so-and-so's coil worked than their competition was basically worthless because of the lack of cylinder pressure. The transition from ionizing in ambient pressure to ionizing in cylinder pressure is not direct and simple.
GM, in the very American tradition of "if a little is good, more is better and overkill is just enough", originally spec'd spark gaps of .060" when the HEI first came out. The coils were capable of ionizing this gap when everything was brand new. Apparently it didn't age well. They backed off the gap spec to .045" or less.
Similarly, say that you have a coil that can develop 45,000 volts to ionize the spark gap, but the worst case cylinder conditions only need 28,000 volts to fully ionize the gap. There would be no point in swapping in a Joe-Racer coil capable of 100,000 volts if the rest of the ignition system can only support 45,000 volts and the cylinder doesn't need it anyway. The voltage needed to strongly ionize the gap is all that the system will ever develop. Anything beyond is just excess capacity that made the people who sold you that Joe-Racer coil that much richer.
If when you install that Joe-Racer coil you also increase the spark plug gap, then you'll start to use more of that excess capacity. Beware though that if the cables, cap, and rotor can't contain that increased voltage that the increased gap will not get properly ionized because the extra voltage 'leaked' to ground. At present the practical upper limit for spark gaps appears to be about .045"
Always remember that electricity is lazy. It will always, always take the path of least resistance.
The trend in the last decade or so is to increase the duration of the spark rather than simply increasing it's voltage. This is much harder to do than just increasing the turns ratio of the coil. This is what the MSD's and other ignition boxes like them are, in part, trying to do.
Some of the alternatives to electric spark ignition are also pretty wild. Things like laser ignition and plasma ignition have been tested. The best is no ignition system at all. That is called "HCCI" or "Homogeneous Charge Compression Ignition". HCCI is basically detonation, but the air/fuel mixture is so thoroughly mixed that the detonation occurs at the exactly perfect point and the engine runs correctly. At my work we have achieved HCCI, as have others. No one has been able to do it consistently and repeatably. I suspect that by the time the technology exists to do so internal combustion engines as a whole will be archaic.
The best is no ignition system at all. That is called "HCCI" or "Homogeneous Charge Compression Ignition". HCCI is basically detonation, but the air/fuel mixture is so thoroughly mixed that the detonation occurs at the exactly perfect point and the engine runs correctly. At my work we have achieved HCCI, as have others. No one has been able to do it consistently and repeatably. I suspect that by the time the technology exists to do so internal combustion engines as a whole will be archaic.
Mark on the outside where the ground electrode is. When you screw it into the head you use washers of different thickness' to set it to stop with the electrode in some particularly desired position. Sometimes that is with the electrode as far from the intake valve head as is possible. I'm not up on all of the ideal goals, just the basic mechanics of the process.
I never would have thought the position of the ground would matter, thanks for the explination. More hp, mileage, etc?