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I just finished replacing my stock plugs which I thought were AC's as per the owner's manual spec-but to my surprise they were denso's. the Gaps were pretty consistent between .058-.060. I put in a set of NGK TR55's gapped at a tight .055. The install took about an hour. I should have replaced the stock wires while i was in there-they look pretty wimpy for such a awesome motor. I'll order the taylor's next week before i go to the track to see if I can improve my numbers.
 

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Spark Plug: Technical Service Bulletins Ignition System - New Spark Plug Type/Gapping
Bulletin No.: 03-06-04-060
Date: October 24, 2003
INFORMATION
Subject:
Information on New Spark Plugs and Gapping
Models:
2004 Buick Ranier
2002-2004 Cadillac Escalade, Escalade EXT
2003-2004 Cadillac Escalade ESV 2004 Cadillac CTS-V
1997-2004 Chevrolet Corvette
1998-2002 Chevrolet Camaro
1999-2004 Chevrolet Silverado
2000-2004 Chevrolet Suburban, Tahoe
2002-2004 Chevrolet Avalanche
2003-2004 Chevrolet Express, TrailBlazer
1999-2004 CMC Sierra
2000-2004 CMC Yukon, Yukon XL
2001-2004 CMC Yukon Denali, Yukon XL Denali
2002-2004 CMC Sierra Denali
2003-2004 CMC Envoy XL
1998-2002 Pontiac Firebird
2004 Pontiac GTO
2003-2004 Hummer H2
with 4.8L, 5.3L, 5.7L or 6.0L V-8 Engine (VINs V, P, T, Z, G, S, N, U - RPOs LR4, LM4, LM7, L59, LSI, LS6, LQ9, LQ4)
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, P/N 12571164 with AC Delco P/N 41-985, is gapped to 1.01 mm (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.
 

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vortech said:
I just finished replacing my stock plugs which I thought were AC's as per the owner's manual spec-but to my surprise they were denso's. the Gaps were pretty consistent between .058-.060. I put in a set of NGK TR55's gapped at a tight .055. The install took about an hour. I should have replaced the stock wires while i was in there-they look pretty wimpy for such a awesome motor. I'll order the taylor's next week before i go to the track to see if I can improve my numbers.
Yes my 02 had Denso's in from the factory as well. I went with the stock replacement plug AC 41-985, and it feels a little down on power. The gap for this new plug has been changed to .040 and says not to change it. When I get a chance I will use the Denso's again gapped at .055. Mine showed .060 with 45K on them.
 

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I had the denso's stock. Replaced them with the AC Delco iridium plugs (made by denso and badged as AC/Delco).

If you use these check the gaps before leaving the store. They say that you can't regap them, so if they are off you have to swap them for another.
 

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i had bosch platinum +4's in my c5 for about 500 miles....they took a dump. ive got the ac delco iridiums in now and she is quite happy
 

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I run the NGK Tr55's and gap them at .060. They work great and are dirt cheap, so I replace them every year before the fest, probably not necessary, but old habits are hard to break!
:yeadog:

Jimbo
 

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Like someone said, the stock plugs are Densos badged as AC Delcos.

I wouldn't wait too long to change plugs, Iridium or not. I've used Denso Iridiums and TR55s - and I feel a significant difference when I change plugs at, or around 15k miles. I told my friend the same thing and he swapped out his plugs on his C6 with 14k miles. He felt the difference I was talking about.

Plugs are cheap insurance.

Alex
 

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Ok,

I need to get plugs again and being there are no stores around here that are any good, I need to mail order them. And I can't remember where I bought them last time ( TR55s). Need some suggestions please.
 

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vortech said:
I should have replaced the stock wires while i was in there-they look pretty wimpy for such a awesome motor. I'll order the taylor's next week before i go to the track to see if I can improve my numbers.

Magnecor KV85 Race Wires are a better choice.
Reason: 200 windings per inch, and don't use "resistive enhancing" coatings which can break down in other wires.

More plug info
http://www.z06vette.com/forums/showthread.php?t=88774&highlight=tr55

Wire info
http://www.z06vette.com/forums/showthread.php?t=85325&highlight=Magnecor
 

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Backlash said:
Ok,

I need to get plugs again and being there are no stores around here that are any good, I need to mail order them. And I can't remember where I bought them last time ( TR55s). Need some suggestions please.
Most of the vendors on the right carry them.

Alex
 

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Backlash said:
Ok,

I need to get plugs again and being there are no stores around here that are any good, I need to mail order them. And I can't remember where I bought them last time ( TR55s). Need some suggestions please.
Sent you a PM. Don
 
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