It can make a world of difference. The gap range is usually about 10% of the gap, and I always set it to the LOW end of the gap, I've found that the engine typically runs better that way. The voltage required to jump a given gap is a linear function, so a 10% increase in gap size requires 10% more voltage to jump the gap. But you should have plenty of voltage to spare if your ignition system is in working order. And, as the plugs wear, that gap opens up (albeit very slowly), so you may as well start on the low end of the range.
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