i was at the zone yesterday and they do carry them and yes they are extremely expensive. Can prob get some aftermarket parts that are cheaper than pickin up 8 of those plugs. Dunno if they make that much of a difference. NGK is about as good as it gets. Delco are good too. Stay away from the bosch platinum 2's and 4's. not as good as one would think.
You can get them at O'Reillys for around $6 each. Honda and several ATV manufacturers went to them for the longer life and self-cleaning properties.
Below is a GM TSB and some other info:
#03-06-04-060 New Spark Plugs and Gapping - dated 10/24/2003.
A new spark plug has been released for use in the above vehicles (list of vehicles with 4,8L, 5.3L, 5.7L or 6.0L V-8 engine). "The new spark plug has an Iridium tip instead of the current Platinum tip. Due to the different tip design, the gap of the spark plug has also changed. The new spark plug, P/N 12571164 with AC Delco P/N 41-985, is gapped to 1.01mm (0.040 inches) when the spark plug is made. The spark plug gap is set during manufacturing and should not be changed or damage to the spark plug may result. Any new spark plug found to not be properly gapped should not be used."
Here is what AC-Delco advertises:
ACDelco’s new Iridium Spark Plugs are the latest evolution in high-performance plugs. The natural properties of iridium, with a melting point approximately 700 degrees Celsius higher than platinum, enable the plug to burn fuel more efficiently and deliver better performance. As a result, the iridium plugs have a minimum service life of 100,000 miles.
Because it is one of the densest materials found on earth, the iridium-tipped center electrode is 50 percent the size of a platinum electrode and 20 percent the size of a conventional nickel electrode.
The secondary microdischarge of the center electrode burns off carbon deposits as they form for superior antifouling performance that, along with the tapered cut ground electrode, offers enhanced flame spread during combustion.
The specially designed electrodes increase the electric field strength at the gap, reducing the voltage required for sparking to begin, for improved cold starting and quicker acceleration.
The application coverage of ACDelco Iridium Spark Plugs continues to grow, with the plugs backed by a 100,000-mile Limited Warranty.
Here's what C4/C5 Specialist said about those plugs
This is to advise ALL Corvette c5 owners of a bulletin, 03-06-04-060, which updates spark plug application and gap.
This states that as of 24 October 2003, part number 12571164 is the replacement spark plug for ALL c5 Corvette, LS1 and LS6.
However, this also shows us that the new gap, of .040, is set at the factory. Any attempt to regap this plug could damage the plug. We are instructed to NOT USE THE PLUG, if the gap of .040 is not there. DO NOT GAP TO .060.
NOW, the largest point to be made here, is that this plug uses an Iridium tip for the electrodes.
This is the first for Corvette.
Others claim to be Iridium tipped, but are NOT in the GM line.
The ACDelco number is 41-985.
So, with that, please be aware of this and utilize this plug from here on in.
Aside from this, I have contacted GM powertrain on the updating to the PCM control calibration for these new plugs and have been told that the latest calibrations are already set up for the revised plugs. Apparently, they knew these plugs were coming, and compensated accordingly.
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