Mr. Motion

Ok, so now I have 42K on my 2005 C6 and feel a need to replace the original set of spark plugs, because - well...just because! Any recommendations? Not looking for something too exotic - just a good-performing plug that folks have been satisfied with. Thanks!

0HorsePowerAddicts

NGK TR55 plugs work great in stock/mild setups.

Neumonic2002

Not sure about the 05' but my 2006 requires a NGK TR5 due to the lower plug gap (.040) Vs the TR55 which comes pre-gapped at .060.

NGK's web site says not to change the gap of there spark plug by more than .008.

So look at your specifications for your plug gap and go with whichever plug fits the gap!

RichieRichZ06

Stick with the Delco Iridium plugs that came in your car. They have almost no issues in stock cars. Do not change to a crappy aftermarket plug unless going FI, N20 or a heads and cam package. I have seen a lot of stock cars having issues with NGK cheapo plugs lately. Most of the issues are mis-fires and carbon tracking on the plugs.

I have a Trailblazer SS here today for a mis-fire code. Swapped out the NGK's and it went away. Same thing on a Cadillac STS last week.

MP35N

There have been a few threads going around about the stock plugs having the gap set all over the map. I decided to put in a set of NGK iridium TR55ix 's. These are not that easy to find nor are they cheap plugs. What surprised me is that at least on my base '08 after 42,000 miles, all of the stock plugs that I pulled out had gaps that were exactly the same. Furthermore, the shape of the NGK iridium plug and of the stock Delco plug is the same. I believe that they are made by the same manufacturer.

Mez

I pulled out the TR55 installed by my tuner and put in new OE AC/Delco plugs. I agree.....I don't see a reason for a stock or near stock LS engine to use anything else.

I posted this before but if you want to use NGK plugs and want to stay with the factory gap of .040" then get the NGK TR5 not the TR55 which is designed for a .060" gap. I have not checked lately, but NGK's website incorrectly listed the TR55 for the 2005 Corvette. I contacted NGK and they confirmed the website was wrong.

I did some research on the subject of spark plug gap. If you have FI or NO2, there is a valid reason to actually go to a smaller gap than .040" to avoid a misfire. The higher the cylinder pressure is, the more dense the air/fuel mixture is, and the more resistance there is for the spark to jump the plug gap. If a engine runs a very lean mixture, then there may be a reason to go with .060" gap, in order to fire but I doubt it.

torquetube

I went with the OE Delco Iridium. Note that the original plugs in your '05 have been superseded by a different part number; a forum vendor can provide you the right one.

Did wires at the same time (around 60K miles). The improvement in low-RPM smoothness was very noticeable.

Mez

Yes, I found that out the hard way. I couldn't find the original part number anywhere.

Wass

Stock C6...replace with stock plugs.

3 Z06ZR1

Ngk is far from a crappy plug. They are better the rest of the copper core plugs. It is the plug of choice of lots of Corvette owners. I used them since 75 and never had a problem. In Bikes and Cars. They are very uniform and work well.
That said the Iridium 's work well too and will last longer.
I still rather have NGK's. They do make a Iridum and for sure it would
be better than a Delco.

3 Z06ZR1

The 100k plug tune is crazy. I changed plugs and wires at 70k
on my pickup. Big diffference. Some people just can't tell the difference.
One member waited till 100k and said the new ones ran the same

3 Z06ZR1

Gm put the LS motors plug gap all over the map.
For starters they come with 4 plugs or less the same gap the rest are
either way. More or less gap. Gm has NO quaility control on plugs what so ever. The 98 model year had a .060 gap in the Camaro
and ..050 in the Corvette. The have put out anywhere form .040
to .060 on different years.

Use a MSD wires and run the .060 gap for best results! With the tr-55

Xwet

What ever happened to the guy selling the $100.00/ each plugs? Did anybody get a set?

Neumonic2002

I had the TR-55's in but just switched them out for the TR 5's. I had a factory wire that cracked inside the boot and wasn't sure what my rough idle/low rpm problem was so I bought 2 sets of the TR 5 and indexed them just for grins, oh and switched the factory wires to a new set of MSD's...car runs and idles much smoother but hey, i did have a cracked wire

RichieRichZ06

The gap issue has been changed for quite a while. The original gap was supposed to be .060 for the non-iridium plugs. Since about 2005 or so, GM has recommended the gap to be set at .040 on all Iridium plugs.

The original part # was 12571164, but has changed to 12609877 and then most recently to 12621258.

NGK might be better then most copper plugs, but compared to an iridium, they are not superior in any way for a stock application. I have seen multiple issues recently with people following what the forum says ans installing NGK's in their stock C5's and C6's. Contrary to most peoples beliefs, the forum is not the end all/know all for things like this, nor is all the information posted always correct. I would bet that in the last year, I personally have seen over a dozen issues with non OEM plugs and more specifically, copper core NGK's.

Don't get me wrong, NGK makes a good motorcycle, ATV, Jet Ski plug, especially for 2 stroke applications but I am not a fan of them in stock applications on most vehicles.

RICH

RAT

For your 05 go with the NGK TR5IX plugs. The gap is at .40" and they are a good iridium plug. Do check your gap before you install them.

HuskerBullet

I've never used Iridium plugs, yet, but probably will switch to them when needed.

If one looks at the Chemical Periodic Table, you'll find the atomic number for Copper is 29 where for Iridium it is 77 (protons in the nucleus) and both are basically in the same grouping as far as valence numbers (outer shell of electrons). What does that mean? First, Iridium is more than double the density of Copper which will supposedly allow it to last much longer, and because it is in the same "grouping" as Copper (alongside Platinum and Gold) it will have a conductivity that is better than Copper. However, it is a more difficult metal to obtain from this planet, hence the expense.

It boils down to one thing.....to each their own as to what they want.

Oh, and don't forget to buy two sets of plugs so you can index 8 of them to the intake valve, then return the other 8.

30YR W8T

Installed these in my 05 and it did make a noticeable improvement.

gregsz06

try looking at the E3 plug website, you dont have to index those plugs, their not iridium though. worth a look

RAT

I've read of this as well. Is there really that much difference with the indexing of the plug? I get the whole visual of what's going on but is there specs for this practice?

Thanks