[Hib Halverson]

The original spark plug for the LT5 was the FR1LS, at the time, GM's coldest spark plug for production engines. Right at the LT5's 1990 release, GM changed that to the FR2LS because of concerns about "pre-delivery" plug fouling in engines on dealer lots.

Other than those who own waxers and trailered show cars or others which are subjected to frequent starts without warm-ups, no Zroner needs to worry about pre-delivery plug fouling.

The AC "1" heat range crosses to the NGK 6 and the Denso 20 heat range.

With due respect to Corey Henderson, who's one of the better LT5 guys out there, the NGK 5 heat range is too hot a plug for anything other than "non-sporting" driving. If you run your car hard at all, you need at least one range colder.

At one time I used the Denso IT-20 in my LT5 but, later, in the early-'10s, I went to the IT-22, one range colder than the AC "1" heat range. For the type of driving I did with my modified '95, that was a good choice. I had hot coils so I gapped them at .045-.050-in.