I can't say that I have seen any. I've run autolites and NGK in the Chevelle. Heat range is probably more of an issue than anything. Maybe if you are using a street type Resistor plug in a race engine it MAY do something. But even that is a stretch with todays plugs.
Well, it depends.:devil:
On whether you are replacing plugs with a hundred thousand miles on them, fouled, gapped wrong, cracked porcelain, wire not snapped on securely, etc....
Who's operating the dyno......
Ever hear the saying "The dyno can be adjusted until we achieve the results your test requires."
We can simply dyno the engine with plug "A" at 3:00 PM when it's 103* in the dyno room with 80% humidity to establish our baseline......Then test the special, whiz-bang, super-duper, latest-and-greatest, fancy spark plugs at 6:00 AM when the dyno room is in the high 70's with 40% humidity and voila.......5 to 15 HP difference.
I never had any luck with Champions in a SBC. Never lasted more than a couple weeks for me. Holley’s were junk too. Usually use Autolite or Motorcraft with success. I normally step up to a better style (double contact etc) than the old stand by’s. I always check the factory gap even though they say they are pre-gapped. I had a friend that had to put a one higher heat range higher in #8 in a built 350. That port would foul the plug and solved the problem with a one step higher heat range with a clean burn.