Since yesterday was a holiday, I woke up early to install new plugs and wires on my 103,000 miles 2001 Z06. I ordered AC Delco iridium plugs and GMPP red wires from GM Parts House (thanks Gene!). Took me about 3 hours to get it done. The hardest one was #7 of course, but even that one was nothing compared to the nightmare of changing plugs and wires on my old '94 C4 . I completely ruined 3 wires, where they completely came apart as I yanked them off of the plugs. All the plugs came out quite easily, though. The old plugs were way out of spec - all were between .55 and .60 gap. I used simple tools, including a 3/8" rachet, a few extensions, and a swizel for a few of the plugs at the back of the engine. Cleaned up a bit under the fuel rail covers and I was ready for a test drive.

Immediately upon start up I noticed a big difference. The idle was noticably smoother. Once I got it up to temperture, I made a few high RPM runs. Huge difference here as well. Before the repair, my car would have a bad knock at anything over ~5500 RPM. With the new plugs and wires, my baby was singing happily at over 6000 RPM . I mean night and day difference. I couldn't be happier with the results!

 

You got me thinking. Lately, I find that my engine is not as happy at high rpm's as it used to be. I keep thinking that it's my imagination but I'm convinced it's lost some power in the upper rpm range. Did you have any codes at all before you changed out your plugs and wires?

 

isnt .60 the original spec of the plugs then it changed to .40

 

No codes. It was just not happy in the higher RPM range.

 

Not sure about the original plug gap (I thought it was .50), but the new spec is .40 as you state. The AC Delco iridium plugs all came pre-gapped at .40, so there was no adjustment needed.

 

Just curious, how many miles were on your plugs? I've got 40k on the originals and I'm considering following your lead. Did you use anti-sieze? I have in the past but I've become confused by discussions on this site.

Okie

 

See this site

http://www.ngksparkplugs.com/pdf/DYK_5Points.pdf

 

This was one of the references that has caused me some confusion, even though it does include some interesting and valuable information.

I plan to use the AC plugs as the OP, so that was what motivated my question about anti-seize. I am still interested in the actual life of the original plugs in my '02. I'm sure they would continue to function for 100k miles but I don't need to wait that long if, even the slightest improvement can be gained.

Okie

 

Here in CA, the tailpipe smog test results are a good way to tell if something is wearing out, has a leak, or has failed. The last time (1 year ago) I had my C5 tested with 42,000 miles on the odo, my HC and NO levels were very low, indicating that my plugs are most likely still in good shape.
My Mazda HCs were steadily getting worse, not because of plugs/wires/rotor, but because an intake manifold leak was slowly getting worse. Once that was fixed, smog results look better.

 

Ive never fund a reason to use antisease or anything on my plug threads. They go in and out without a problem. Just always be sure that the block is completely cold before doing anything.

Yes the OEM spec was .060 and cahnged to .040. If you ask me .040 is too small. I put my NGK's to .050 and still acheived a smooth idle and less missfires. I have just always heard that a wider gap makes a more powerful combustion.

 

I had 103,000 miles on my car with the factory plugs and wires. Yes, I used anti-seize on the threads and silicone on the wires.

 

Changed my plugs and wires a few months back. I used anti seize on the plugs, and silicone on the wires. No problems so far. Runs nice and smooth.

 

I used plain old copper NGK plugs & MSD wires. Couldn't be happier. I won't get as many miles out of those plugs but no more than I get to drive it, it's not a big deal to change every couple years since they're more inexpensive. No anti seize & used silicon in the wire boots.

 

I reduced the ignition noise on AM radio somewhat when I changed to 0.40" irridium plugs (and new wires) in lieu of the originals which were all close to 0.60".

 

A drop of oil is recommended

 

Thanks for the info. That is my plan also and even though I've only put 40K miles on my plugs, they are ten years old and have the .060 inch gap.

Okie

 

Like slant said. GM says do not use anti seize. Use a couple of drops of oil. Anti seize is also an insulator. Not good blocking the voltage circut to ground.

 

Just replaced the stock plugs and wires on my 02 Vert. Even though at 10 years and 25k the car seemed to run fine, passed smog easy and didn't use a drop of oil, I wanted to see if any improvement was possible.

I put in the GM Iridium plugs and Taylor 10.4 mm Pro Race Wires. Definitely starts faster and runs smoother and stronger. Not debatable. Very pleased. Also, the slight AM static noise has been completely eliminated.

I was surprised at how bad a few of the plugs looked and the wires were in very poor condition. With respect to the sad condition of the wires, all I can surmise is that it's a very hot environment in that engine bay and the stock GM wires aren't exactly race quality even when new.

The iridium plugs are a whole new ball game. The gap they come with is the gap they need for optimum performance and one CAN NOT AND SHOULD NOT attempt to change the gap to any other spec without damaging the iridium tips. One cannot compare optimum gaps on standard plugs or platinum plugs with the required gap on iridium plugs.

The tip design of iridium plugs from NGK & GM are very different. I decided to trust GMs claims of extensive design testing which led to this much smaller tip technology. No way for us to really evaluate such nuances. It's just a matter of gut feeling and trust ... Different for each of us.

I now have newly installed shorty headers but can't stand the look of wire socks so I will just try to keep these new Taylor wires spaced optimally and keep an eye on them. They are vastly superior to the GM factory wires.

Can your plugs and wires run 100k? Probably. The question is, at what point do they begin to operate less than optimally and how much of a gradual but continuing reduction in optimum performance are you dealing with at 25k, 50k, and 75k?

From now on my plugs and wires will be changed at 20-25k. It's just not that much money.

 

This may very well be the reason your wires and plugs were degraded. That extra heat radiating from the headers shortens the life of belts, hoses, batteries, and spark plug wires.

My CAI mod pumps much more cold air into the engine bay than was available with the stock configuration. I'll bet if I were to look at my plugs, they'd look just fine. The wires do look fine. I did check with the mechanic at the dealership and he told me that he's seen many plugs go well beyond 40K miles without problems. That's why I am in no rush to change them.

 

I appreciate your thoughts. However, I perhaps should have clarified that I changed the plugs and wires two days after I had the new headers installed so the damage to the wires and plugs was done while using stock headers. I have now modified the post to reflect this fact.