Plug gap

Valman said
There seems to be some diminishing returns with widening plug gaps. Peak HP is one thing, but again when an engine is at peak power/load/torque you’re going to be around peak demand for your ignition.

If your ignition can’t supply the output, it can’t keep supplying the needed spark at peak. A bit like the duty cycle of a welder. Spark may be good at idle, but run out of steam at peak demand.
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It's not diminishing returns. It's abuse on the ignition system. Wider plug gaps increase resistance and that builds heat in coils and ignition boxes. There's no need for anything over a .045" gap. Ever. You buy into the crap if you want to, but it's just that. Crap.