My 97 Z has a few mods. K&N Cold Air Intake and Headers. I still use the AC Delco spark plugs. I notice people using NGK TR55 or Autolite 104. I see that their using a gap difference, i forgot the numbers, compared to the AC Delco. Can someone explain what the gains are to me? Can i use the NGK or the Autolite, or will i hurt the engine?

 

You don't need to worry about a colder heat range or smaller gap with your car. Just use recommended stock replacement plugs and stock gap. NGKs are great plugs, the others are fine also - any cross referenced plug will work. When you make a lot of power, then a colder heat range is necessary, and adjustments to heat range and gap should be made for forced induction & nitrous.