I just pulled the NGK iridiums (on a stock coil and gapped at .040)... I was getting some pre-ignition and finally decided it could be caused by the plugs instead of the SCT tune..

the plugs only had about 1k miles on them, but they came out that brilliant rust color, which I'm told is good...

I think I paid $9 ea. for them.. I replaced them with Champs, and so far- so good.. I kept the NGK's though, and because of what Unreg contributed above.. At some point in the near future I'll be upgrading coil, and it will be nice to have options to see which works best..

just my .02...

autolites in there when i bought it. been using NGK Vpower since. no issues. just picked up a set of blue silicone NGK plug wires. they are beyond awesome. proper boots, strong connectors, and theyre numbered for the correct plugs!!!! .40 gap i think

i was pinging with autolights 3923 , there great at first though first 5 k noticed power 1st run with them on. now i installed ngk v-power they seem to work well no ping yet running 93 sct tune . i had the iridiums and they were the wost pinging plug i ever installed ! ! i will try stock champs next tune up and compair them all !

Our stock coils don't make enough voltage to properly fire the expensivum plugs. Lots of aftermarket coils make no more voltage, or not significantly more voltage, than our stockers.

As long as I'm cluttering up the thread: I haven't got around to pulling those spendy Laser Iridiums to see what they look like, but so far I have no complaints. Having got back up into the mountains where I belong I'm running 87 octane with the SuperChips towing tune and haven't heard a ping yet even when I tried to make it happen. The other day I was grossing about 6400 pounds and had it in overdrive pulling a moderate grade at 55MPH, pushed down on the pedal to just shy of where it would have downshifted, and heard not a sound.

So far, so good.

NGK V-power. Mine have over 40k on them, half of that is with boost, still at the .040" gap I installed them at.

Pinging bad even worse now.
If I ran 3923's and gapped them at .035, would that reduce the knock enough to use 89 octane gas till I get my plenum fixed this winter?

NGK V-Power .40

I use Champion RC12YC or 3344. Gap? Usually the gap listed on the radiator support, but 0.08 does it fine as well.

0.08!?
WUT?



I am running 3923's at the stock .040 gap. Runs great with my plenum fix.

Oops, sorry... meant to say 0.035. I got mixed up between my small engines and this truck there cause many mowers I have here I gap at 0.080. But if you do a lot of idling with your truck then a 0.040 gap is good, we do a lot of high RPM with this so a smaller gap is necessary.