Moral of the story is one of the plugs that was put in was likely damaged. We just made several 140+mph passes with those exact plugs for several thousand. I surely wouldn't put in a set of plugs that could be a potential problem when there are thousands of $$$ on the line.They aren't the kind of plug you want to cruise around and idle all day with. They will carbon up and or lead foul easily. There's no plug or gap exact number that's going to make a huge difference in how your car runs. These plugs are typically used when you are over 125 hp per hole and plan in making some hard runs. I don't rec attempting to re-gap them
We fired them without a problem right out of the box with a stock ignition. A known good stock ignition with an old GM module. 6000rpm and over 800hp
I'd stay with the stock plugs for that
They worked great in my car for about 30 miles. Then I got loud spark knock with hardly any foot in the throttle. I use NGK UR5's now. They just seem shinier and heavier than Delco plugs. Shiny is good, right? I once had an Autolite plug break while accelerating. Heard a loud back fire. It left the plug wire just hanging free with the porcelain part still in it. At least it wasn't hard to diagnose.
