horridohutch

Put Iridium plugs in my 95Z28A4 10k miles ago, 1 took a dump last spring and now today... another, whats up with these expensive, supposedly "great" plugs?

Kevin Blown 95 TA

I never used them but once asked the NGK engineers what they thought and they had positive reviews of them for forced induction applications. They said it was a good plug. Either way, a plug ought to last a lot longer than 10k miles unless the engine or the installer kills it somehow.

You need to post more details if you want a detailed answer.

96capricemgr

Iridium and platinum are used to reduce gap errosion and therefore plug longevity, they wont make more power.

How are they failing?
If the fine electrode is getting lost I would consider detonation as a possibile cause.

horridohutch

First time it was a miss on #7, replaced plug and miss went away. Starting to get the same problem now on #4. I felt the miss starting up and shot some water out of a spray bottle to find the cylinder that wasnt firing, on the header tube. Pulled #4 and it looked OK, a little reddish brown to black soot with the insulator white. I am going to replace them all tommorow night and get a better look. They are Champion Iridium.

raulz28

Just out of curiosity. Why are you using Champion plugs? You are the first person I've heard that is using them on a GM engine.

horridohutch

Why did I choose Champion? Bad choice I guess... I thought a plug is a plug.

Injuneer

What is the heat range of the Champion Iridiums? Is it the correct heat range for your engine?

Actually I guess I would be the second person raulz28 heard using Champion plugs. I use their S57YC racing plugs with a 300-shot of nitrous, and they work great.

horridohutch

Thanks Fred, now I dont feel like a total idiot. I will check tommorow on the heat range, gonna replace with OEM AC Delcos tommorow anyway.

MachinistOne

I really like the iridium plugs, they stay clean, they last a very long time, and they have excellent spark kernel exposure. I have dynoed back to back in quite a few vehicles compared to a regular copper plug and seen 3-8 hp. Not a significant gain, but still...

Injuneer

I have yet to see a complaint about the Iridium plugs. The NGK Iridium plugs seem to be a popular replacement.

horridohutch

Yes all of the things I see in forums say the NGKs, as far as the Iridiums are concerned. I have actually seen some negative on the Champions. Well the AC Delco Platinums are on the bench....... on a mission after work tommorow.

dizwiz24

Iridium plugs are garbage and are not forgiving. I had an o2 sensor fail and the car ran rich. The iridium plugs, their smaller electrodes foul quickly in any circumstance less than 100% ideal (since iridum is expensive they rip you off by giving you as little of it as they can). This left me with a no start condition until plugs were replaced.

And we all know how easy the plugs are to replace.

I've even heard of a guy who regularly started his corvette in the winter, but didn't let it run long enough to get hot. That procedure was enough to cause the (small) electrodes to soot up and foul, leaving him w a no start condition until plugs were replaced.

And a lot of us run big cams here, imagine how rich and nasty those run at idle. No way would I want iridium plugs.


Now, if they would make the electrode the same size as a copper plug, then yes I would consider (if they weren't so expensive)

96capricemgr

I would think that the smaller tip on the iridium plugs would keep the arc jumping from the same point and keep them cleaner.

Far as plug brand, who cares, heat range is what matters, sometime cross referencing heat ranges does not work but that doesn't make a brand bad, matter of fact sometimes it can be good to play with a few brands because you might find champion has one that falls between two NGK heat ranges might be just right.

Like I said above though if the iridiums are troublesome I would investigate detonation a bit, whether it is too hot a plug or in the tune or something.