spark plug basics as I understand them.
you want the tip to run hot to avoid carbon build up and fouling from other deposits like oils. but if you get it too hot, the strap can start glowing and light off the mixture before the spark fires, causing detonation. which kills everything. so that's where the colder heat range plug comes in.
so it's a trade off there. as for hp, a plug can't make more hp, it can only reduce miss fires, which from the stuff I've read actually happens a lot even in smooth running engines. I guess sometimes a electric spark can jump straight thru a fuel/air mixer and not light it.
things like where the spark is located in the chamber can effect hp, but in general that's up to the engineers that made the hard ports, you can't really change a plug location. at least in a ls. the old Gen one heads did come in straight plug and angle plug option heads. which was better, I believe angles in most applications?
now you can change tip length, but then you run into hitting pistons, so you don't have much there either.
basically real world, without major changes to compression, either mechanical or by boost or nitrous. if you're not seeing timing retard in your logs, I wouldn't change plugs from stock heat range. If you do see knock retard, you can try a step or 2 cooler to see if it goes away but that's probably going to lead to changing plugs more often if you didn't raise static compression. which isn't really a thing these days in ls builds, since they have high compression stock compared to say a 80s smog motor you went from 8.5 to 10.0 on during a rebuild.
as usually the further you get away from stock, the more often you do maintenance so changing plugs more often is acceptable in a power adder build than a daily driver.
guess the same could be said about types of metal used in the plug. a straight up plug without any platinum or iridium usually run just fine when new, and high hp drag cars might even run a standard type plug because they pull them often to check tune up. I've read you can see a line form in the ground strap when tip hits a certain temp. so you can see the results of that glowing tip. and adjust timing in hopes of keeping it from definition or worse just melting off.
they replace them often and don't worry about high mileage fouling. but if you're trying to get a 100k out of a plug, that's when the expensive metals that don't wear away and can run those high Temps to avoid fouling with today's oil burning pvc setups.
everything on forums throws around ngk as the ultimate plug, but oddly I've seen a few cases on turning forums for older Gen 1 sbc where guys chasing what they think is false knock on the logs. engines that aren't considered on the limiting timing, a/f or compression wise but showing knock counts. as a test would just replace their fancy experience ngk with a local parts store cheap plug, of all things usually a auto lite and bam, false knock gone. bow why? no clue. and looking back, since those was a long time ago I spent time in those forums which are all dead now anyways. did these guys get counterfeit ngk's? honestly never even knew a counterfeit spark plug was a thing back then. and no one thought to ask where they got the plugs. so maybe they were the first victims of ebay parts lol.
I saw all that to say just buy the oem acdelco plugs from a reputable place haha. the more you know about plugs the less you know about plugs and the bigger the headaches and brain damage get. but I say that to say there really isn't any best brand of plug. if you have issues, try a plug till you find one that works for you.
