It all depends which plugs you're using, and if you're N/A or F/I. Stock gap for the platinums is .060. The Delco Iridiums should be pre-gapped at .045. I keep my NGK TR55's at .055 which is straight out of the box. Alot of FI guys run NGK TR6's at .030 to .035 I believe.
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NGK TR55 are pre gapped at .059" according to the NGK part # key. The first 5 is the heat range and the second five is the gap. This series of plugs have a heat rating of 4 (hot) to 6 (cold) so 5 is in the middle and gaps of None = .039" ( ex TR6 ); 5 = .059" and 0 = .080".I noticed the TR6s I installed were a very loose .035" when I installed them but they were close so I left them. I tried adjusting one but it was a real pain for the small difference so I left the rest and adjusted the other one back to the factory setting.
i pulled my stockers out today to get ready for the radix and just for the hell of it i checked them... at 5000 miles....35 is what i got
The stockers in the Avalanche are gapped at .035 from the factory for '05 ???? That seems weird because the stock gap is .060 on all the Silverados for '03 from the 4300 right up to the 8100 according to my Owner's Manual. Something new?