Spark Plugs

[GRRRR8]

Most people do not realize that the factory Delco plugs are Iridium and made by Denso. There is not much reason to change on a N/A application.

Here are some part#s and plug info:
14mm thread .708 reach tapered seat Gap .040

Delco 41-985
Denso ZTJ16R10
Autolite XP5245

All of these plugs are Iridium and factory heat range.

[swatt444]

Thanks for the info on the plugs. What do you feel is the best frequency to replace them? Since they're made from unobtanium, they should have long life, but I was just curious.

[Crazy Paul]

INFO:
The owners manual has a listed service interval of 100,000 miles for the stock OEM spark plugs.

[swatt444]

Thanks much! I need to grab an owners manual for the car. Last time I had it serviced, it magically disappeared...

[Crazy Paul]

http://members.iinet.net.au/~pjsadler/2008_pontiac_g8_owners.pdf Free Download.

[swatt444]

Even better! Thanks!

[desertg8]

ok Charlie, I got the IT 16s. The porcelin on the ones you are showing go into the head more. On the it 16s they do not. But Denso has it on their charts as a direct replacement. It is the u groove one with a .4 mm electrode. Supposedly meant for more performance. But it does not protrude into the head as much.

[norm8332]

ok Charlie, I got the IT 16s. The porcelin on the ones you are showing go into the head more. On the it 16s they do not. But Denso has it on their charts as a direct replacement. It is the u groove one with a .4 mm electrode. Supposedly meant for more performance. But it does not protrude into the head as much.

Is that "Performance" plug colder than stock? My Autolite AR103s have a cut-back electrode to supposedly reduce the temp. for example.

[desertg8]

nope. it is the stock heat replacement. but if you do a google and pull up it 16 it will clearly show the porcelin does not protrude into the head as much. and denso states on their site it is a direct replacement.

the picture of the one charlies has does not have the u groove, does not have the thinner electrode. also the it16 has copper inside. but again it does not protrude into the head as much which maybe could detur performance.

i just do not know.

[GTPprix]

The Spark Plug Specifications have changed on the G8 new part is:
41-110 (12621258) Denso

SOME G8's Did come with NGK's as OE due to some supply issues, I've only seen a few but my GXP had NGK's in it when I got it. Food for thought :)

[13 QTR]

so......charlie....what do you recommend for a built LS3,but with stock compression(maybe just a hair under)? I currently have the NGK tr6's in mine now... If changing them is worth only .05hp.....I'll leave them alone.....

[Identity Crisis]

I am using the E3 Plugs and like them. No difference in performance that I can tell.

[chuckie669]

http://members.iinet.net.au/~pjsadler/2008_pontiac_g8_owners.pdf Free Download.

Awesome Link to the manual. That's going on my phone for search reference.

[desertg8]

On the denso it 16 their reach is .62 inches. For the g8 it is .708. I had the IT16s. They seemed ok. But I would not recommend them since they do not protrude into the head as much.

So if you want the high performance denso it will work. There is a oe denso which Charlie mentioned. That has the .708 reach.

[mi04se1]

Im getting headers put on in a few weeks. My question is would NGK TR6 hurt anything? My mods are in my sig. I only have about 11000 miles, but since the plugs have to come out, I might replace them if a one step cooler will work.

[c5racr1]

got heads cam and headers with tr6s work fine replace bout every 10k

[-Ray-]

Im getting headers put on in a few weeks. My question is would NGK TR6 hurt anything? My mods are in my sig. I only have about 11000 miles, but since the plugs have to come out, I might replace them if a one step cooler will work.

Since the plugs are going to be out, you might as well put in a new set. I don't see where you need to go to a colder plug.