Spark Plugs
12-14-2011, 11:43 PM
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Spark Plugs What are the best spark plugs to run in an LS1? I have heard that TR55 are a good choice, but i also heard that they foul out. Another opinion that i was given were the AC Delco Iridiums that come stock in the motor. Any opinions and experiences would be great. Thanks
12-15-2011, 01:46 AM
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The original plugs for these cars were platinum, not iridium. The current factory replacement plug is iridium though.
NGK TR55 is a great plug, but it was not designed to last 100k miles like a factory platinum or iridium plug. They are old style copper plugs that many feel offer better performance than the original platinums. They should last about 20-30k miles depending on how you use the car, and are considerably cheaper than the more exotic platinum/iridium tipped plugs.
NGK TR55 is a great plug, but it was not designed to last 100k miles like a factory platinum or iridium plug. They are old style copper plugs that many feel offer better performance than the original platinums. They should last about 20-30k miles depending on how you use the car, and are considerably cheaper than the more exotic platinum/iridium tipped plugs.
12-15-2011, 02:04 AM
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RPM is right. The copper plugs are cheap, they work well, and are required to be changed at less then 50k IMO. Who would want to leave any plug in longer then that anyway?? 
12-15-2011, 03:45 PM
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Originally Posted by General Motors Corp.
A new spark plug has been released for use in the above vehicles. 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, ACDelco Part Number 41-985 (12571164), 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 to the gap required with the Platinum plug, or damage to the spark plug may result
Anyway, yes it is true that you should not change the gap, per the bulletin. As for it lasting only 10-15k miles, I can't see why that would be true at all. The bulletin makes no mention of a change in plug service life, and since GM literature for the car(s) effected by this bulletin call for 100k mile plug changes with the platinum tip, I can't see why iridium would be any different.
As for aftermarket iridium plugs that may or may not have a different tip design, gap, and/or heat range, I have no idea what the change interval should be.
