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Spark plug preference?!

5K views 9 replies 7 participants last post by  chilliwhiggerE 
#1 ·
I am currently using AC Delco's no gap on my 05' 6.0 GTO. I am running a K&N typhoon intake, and are not gaping the plugs at all. The black smoke out of my exhaust is having me question

Anyone have a preference on plugs they prefer?

Andrew
 
#2 ·
If you don't gap your plugs before you install them you might as well not bother changing out the old ones. 0.040" is the gap you need.

I just put in some NGK TR5 IX iridiums two days ago. 39,000 miles on the clock and the factory plugs were way out of gap spec (as much as 0.060") and the ground electrodes had quite a bit of erosion.
 
#3 ·
#5 ·
When I did mine I gapped the ground electrode with a needle nose, staying away from the post side. I figured the plating on them is probably pretty thin, so they probably wouldn't take well to tool contact.

Even pre-gapped plugs can be out of spec just from bouncing around during shipping, unless they put one of those cardboard sheaths over the electrodes, which I haven't seen in a while.
 
#10 ·
.040 Trust me I tried a variety of gaps in both directions and nothing worked as well as the factory setting.

I also run NGK TR55. I never gap with anything other than a feeler gauge and I set the gap by turning the plug upside down on a block of wood then inserting the blades and lightly tap the electrode with a brass hammer. I feel that this method should be safe for gapping the Iridiums without damaging the coating.
 
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