Plugs and wires

What's the best spark plugs and wires I should get for my 2005 grand price gxp with over 100,000 mi?

AC Delco.

NGK Wire Set RC-GMX107 and TR5IX spark plugs if you're stock. NGK Wire Set RC-GMX107 and TR6IX spark plugs if you're modded (One heat range colder than the stock plugs).

Why would you need colder plugs unless you're raising compression or adding boost?

Originally Posted by lVloses

NGK Wire Set RC-GMX107 and TR5IX spark plugs if you're stock. NGK Wire Set RC-GMX107 and TR6IX spark plugs if you're modded (One heat range colder than the stock plugs).

Who says that?

You want the hottest spark you can get away with, not the coldest.

Plugs that are too cold will only cause misfires, crappy MPG's and performance.

But whoever it was probably didn't tell you that, did they?

AC Delco stock replacements or bust.

That's all you need in the LS4.

It's what GMLS4 recommends. "The TR6IX Iridium plugs, which are one heat range cooler than stock plugs... which is what you want if tuned and/or have mods, helps to keep things running a little cooler and better, for any mods and/or custom tune changes..."

And from NGK directly: "When you need your engine to run a little cooler, run a colder plug. When you need your engine to run a little hotter, run a hotter spark plug. However, NGK strongly cautions people that going to a hotter spark plug can sometimes mask a serious symptom of another problem that can lead to engine damage. Be very careful with heat ranges. Seek professional guidance if you are unsure.
With modified engines (those engines that have increased their compression) more heat is a by-product of the added power that normally comes with increased compression. In short, select on heat range colder for every 75-100hp you add, or when you significantly raise compression. Also remember to retard the timing a little and to increase fuel enrichment and octane."

Dont contradict yourself in a single post.

Originally Posted by matt5112

Dont contradict yourself in a single post.

According to Rock Auto the OE replacement for the 3.8L V6 Grand Prix is a Bosch 7420, where the OE replacement for the 5.3L V8 Grand Prix is a Bosch 7421. These OE replacements have the same heat range rating of 9. So there you can see that the same heat range is used on both Grand Prix engines even though the stock HP changes from 200 to 303. Not to mention the compression ratio is 9.4:1 in the base Grand Prix where it is 10.0:1 in the GXP. Now add that in with a few mods that you already have or plan on doing down the road and you'll see why a colder range is recommended. Running one heat range colder on a stock LS4 won't hurt it at all. But it's a good idea if you're modded/planning to mod.

So the spark plug temps tell you combustion chamber temperatures?

Alright can't answer that, but neither can you. But another reason to drop down a heat range is to reduce KR. Which the LS4, even with a 91 or 93 octane tune gives a lot of KR. You cannot argue with that.

I would look into the LS6 red performance wires and good NGK or AcDelco Iridiums.

I'm not 100% but I think the LS6 red wires will work on the 5.3s, a buddy has a 240SX with a LM7 5.3L dropped in it and some various LS parts added to it and I know he has the red plug wires, but not sure if they are LS1 or LS6 or what variety of length haha

Originally Posted by lVloses

Alright can't answer that, but neither can you. But another reason to drop down a heat range is to reduce KR. Which the LS4, even with a 91 or 93 octane tune gives a lot of KR. You cannot argue with that.

The answer to my question is they do.

Lookup spark plug reading chart.

what is KR?

http://www.grandprixforums.net/what-...here-1507.html (What is octane? KR? Explained here.)

Thanks