1999 Chevy Silverado spark plugs?

1999 CHEVROLET SILVERADO
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SNOBRDRPRO
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Engine Performance problem
1999 Chevy Silverado V8 Four Wheel Drive Automatic 154k miles

i recently bought some new plugs for my truck. Nothing too special just some ngk plugs. They came gapped at 40 and my chilton manual said gap them to 60, so i did. My question is should i have gapped them? Cause ive had some problems with my o2 sensors saying both banks are rich, and im wondering if the spark isnt enough to burn all the fuel? I need to fix it cause its getting horendous gas mileage. Also one of my plug holes are stripped and it only the plug goes in maybe 3/4 of the way. how can i fix that?
-thanks
May 2, 2009 at 4:49 PM
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2CARPRO JACK
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First remove those plugs and install A/C Delco replacements. The plug hole will need to have an insert installed, which is a kit you can purchase, or remove the head and have it repaired without an insert.
May 3, 2009 at 9:05 AM
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SNOBRDRPRO
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ok and for the insert can I do that myself or do I bring it into a shop? If I can do it how do I get the old one out?
May 3, 2009 at 10:54 AM
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2CARPRO JACK
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Yes it is a DIY kit that you can find at most auto parts stores, as far a theld plug, you will just have to unthread it out of the head.When you tap the hole for the insert, be sure to use some grease on the tap to grab the shavings so they dont go in the cylinder
May 3, 2009 at 6:41 PM
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SNOBRDRPRO
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o thanks. could this be the reason that the o2 sensors are reading rich?
May 4, 2009 at 12:23 AM