From ALLDATA for "GM" technical service bulliten posted in 2008. vehicle application 1998 -2002 "LS1' -----This article has been updated with TSB #03-06-04-060BINFORMATION ON NEW SPARK PLUGS AND GAPPING SPARK PLUG GAP............................................. 1.01 mm (0.040 in.)^ A new spark plug has been released for use in certain vehicles. The new spark plug has an Iridium tip instead of the current Platinum tip. Due to the different tip design, the gap of the spark plug has also changed.^ The new spark plug, P/N 12571164 with AC Delco P/N 41-985, is gapped to 1.01mm (0.040 inches) when the spark plug is made.

 

So are you asking what to run? .050-.060 will be fine for naturally aspirated motors unless you have a really high compression.

Parker

 

If you are using the GM iridium tip plug, then use the factory gapping of .040" that is called for in the bulletin.

I pulled out my stock platinums (gapped at .060") and intalled the new GM iridium plugs with the factory preset .040" gap and everything has been fine for a year now.

In my other LS1 I'm still using old conventional tip plugs and keep them gapped at .055".

 

I will be installing MSD 8.5 wires along with NGK TR-55IX plugs that are pregapped at 0.060. Some of the peeps are saying gap at 0.040, and others say 0.050. The 02WS6 is all stock application and I will putting the wires, plugs, ""SLP" air kit, long tubes, corsa 3" pipes and doing all those "free mods", listed all over the place.

 

If you want a 0.040" gap, use the tr5 plugs. The "55" in tr55 is for the 0.055 plug gap, otherwise the same as the tr5 plug which is a 0.040" gap. I just installed the NGK HX ruthenium plugs TR5AHX which come gapped ~ 0.044". Too early to tell for me but most report good results with the HX plugs

 

All of my TR55s have always come out of the boxed gapped at .059". I usually change them to .055" though.

And welcome back to 2013!