fixvet

It's time for new plugs.....81k miles on the clock of my '98 coupe.

I've been hearing about a new or newer AC/Delco Iridium plug. Does anyone know the GM part number? I'm not a racer, just a cruiser that like likes long road trips, so just looking for longevity and better gas mileage. I hear the new Iridium plug is the best to now use but the part number may be different from the plugs offered a year ago. Does anyone know for sure?

Thanks!!!!!

jmohn

AC/Delco (Iridium) 41110

Jerry M.

hamhead

While the price on iridium/platinum has come down recently so it isn't a ripoff as much anymore, I still run copper. Most tuners recommend NGK TR55. Platinium/iridium and getting power/gas mileage increases are marketing gimmicks.

You might get more longevity out of an iridum plug, but for Vette owners who normally want the best performance, taking an hour to change plugs every 25k miles shouldn't be an issue.

fixvet

Thanks Jerry! I'll check these out. What gap is needed?

fixvet

Thanks for this info too! What gap is recommended for a stock LS1 like mine with NGK TR55's?

jmohn

They come pre-gapped at .40, which is what GM recommends. As I understand it, you're not supposed to re-gap Iridiums.

Jerry M.

3boystoys

Never had an issue with gapping Iridiums, the one I got were gapped to .060 so I used the correct tool to gap them to .040, no issues.

Bill McCassey

Jumper11

What about the E3 plugs? Heard they were the new high tech plug that burns fuel better than the single post plug.

ZigZag

I just put a set of NGK Iridium IX TR 51-X in my 99. You can get them at Rock Auto for $51.84. Might as well think about changing your wires also, I changed mine from 7mm to MSD 8.5. Very noticeable difference in idle and acceleration. JMHO

Lt. Dan M.

GM Service Manual for my 99 calls for .060 plug gap. Pulled all my plugs for header install and they are all about .066 with 70K miles on them.

1sickz51vette

I ran these on my car from about 70k miles to 125k with no issues. However others have said they aren't the best for our motors....

vettenuts

That number has since been revised by GM to a smaller value. If NGK, the TR5 would be the plug to use rather than the TR55. The second 5 in the part number denotes a wider gap.

leadfoot4

However, I'll throw in my $0.02 worth..... Bosch Platinum +4s in my car.

bighank

As I remember the Iridiums are gapped differently the the old platiniums.
I also went with the Red GM Wires that are half the cost of the black ones. That was about 40K miles ago. Still going strong.
My new Iridiums were slightly misgapped. Coating is thin that is why they say don't regap them. If you take your time and stay away from the real gap between the electrodes you are fine. Just don't scrape the Iridium off of the electrodes.