spark plug gap
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Joined: Sep 2006
Posts: 80
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From: Nassau NY
spark plug gap
I am going to replace my spark plugs with NGK TR55s. Don't know whats in there now. I have been trying to find the correct gap for these plugs. Most opinions are .040 but I checked the manual and the gap is supposed to be .060. Coincidently the TR55s are gaped at .060 from the manufacturer. Does anyone have any input on this? Thanks all.
Burning Brakes
Joined: Mar 2005
Posts: 1,227
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St. Jude Donor '06
Gap is whatever the manufacturer of the actual plug recommends. Go to NGK and figure out if they are supposed to have 0.060 gap. If they are, then right on! If not, find some that are right...
At least this is what i was told and what i read on the forum...
0.060 in the manual is for the original platinum plugs. 0.040 is a common number heard around here because its the gap on the AC delco iridium plugs that you can order through GM. They are the newest "revision" (iridium vs. platinum)...
I actually just installed 8 new AC iridiums and they woke the car up...then again, 7 of my 8 original platinum plugs had lost their platinum "puck"
At least this is what i was told and what i read on the forum...
0.060 in the manual is for the original platinum plugs. 0.040 is a common number heard around here because its the gap on the AC delco iridium plugs that you can order through GM. They are the newest "revision" (iridium vs. platinum)...
I actually just installed 8 new AC iridiums and they woke the car up...then again, 7 of my 8 original platinum plugs had lost their platinum "puck"
Last edited by Stealthy4; Aug 5, 2008 at 05:38 PM.
Burning Brakes
Joined: Feb 2005
Posts: 752
Likes: 1
From: Tulsa OK
I ran the NGK55 copper plugs for a few years. They were cost effective and lasted about 20,000 miles. Car ran OK. I gapped them at .50
Just installed NGK iridiums - big difference. Won't be going back to the 55s any time soon. They come gapped from the factory at .40.
Just installed NGK iridiums - big difference. Won't be going back to the 55s any time soon. They come gapped from the factory at .40.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
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From: CA.
St. Jude Donor '13-'14-'15
Copper core plugs like the TR55's will wear out faster and increase the gap quicker--So most people gap them closer--The new-age material plugs tend to wear out almost nil so larger gaps can be held almost indeffanately--BUT copper core plugs are far superior for disapating heat and from a performance standpoint much better---Remenber -the larger the gap the MORE tendancy you create for a mis-fire-
PS you don't see NASCAR type engines using platinum plugs or irridium-They strictly use copper--AND for endurnce racing they often run gaps very tight to prevent misfires--
I run my TR55's at .040--------
PS you don't see NASCAR type engines using platinum plugs or irridium-They strictly use copper--AND for endurnce racing they often run gaps very tight to prevent misfires--
I run my TR55's at .040--------
Burning Brakes
Joined: Mar 2005
Posts: 1,227
Likes: 15
St. Jude Donor '06
NASCAR example might not be the best other than simply pointing out that copper is best for performance....other than that, the longest NASCARs usually drive is 600 miles...i dont know about you but i dont plan on changing plugs every 600 miles...
Last edited by Stealthy4; Aug 5, 2008 at 08:05 PM.
Burning Brakes
Joined: Sep 2007
Posts: 1,048
Likes: 300
From: FL
I asked this question to the folks at LG motorsports and they recommended .035 gap on the TR55s. I would not use the .060 gap. I originally had mine set at .055 and it didn't run so well, regapped to .035 and it ran and idled much better. I would replace the wires as well since they have a tendency to break during the process.
Pro
Joined: Jan 2007
Posts: 553
Likes: 0
From: Cape Coral Florida
my iridiums were gapped at .060 when i bought the car and white as chalk now i regapped them at .040 runs better and smoother. tried tr55s at .060 and ran ruff and lost feul millage about 2mpg took them out and put back in denso iridium. ill let you know if the pinging stops in 1 and 2nd gear and if it will run alittle cooler. also i was getting 30 mpg at 80 , 28 mpg with ac on or headlights up
Last edited by superjet701k; Aug 5, 2008 at 10:53 PM.
Team Owner
Joined: Mar 2001
Posts: 25,889
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From: Virginia Beach
CI 3-5-6-7-8 Veteran
FYI the OEM service manual for my 2001 states gap should be .050 to .060. NGK TR-55s come at .055 and Ive been using them w/o issue since my first plug swap back in 2003.
The new delco iridiums come at .040 and that should not be re-gapped. Narrow gaps are only needed for nitrous or forced induction motors to prevent spark blowout. Ideally you want the widest gap possible to promote efficient combustion.
The new delco iridiums come at .040 and that should not be re-gapped. Narrow gaps are only needed for nitrous or forced induction motors to prevent spark blowout. Ideally you want the widest gap possible to promote efficient combustion.
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Le Mans Master
Joined: Aug 2005
Posts: 5,375
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From: CA.
St. Jude Donor '13-'14-'15
On the street a copper core plug can last 20-30K--
Last edited by tblu92; Aug 5, 2008 at 11:26 PM.
Burning Brakes
Joined: Mar 2005
Posts: 1,227
Likes: 15
St. Jude Donor '06
LS1 dont spin to 7K let alone 8 or 9K...
I guess my point is NASCAR and Corvettes are apples and oranges.
Last edited by Stealthy4; Aug 6, 2008 at 12:07 AM.
Le Mans Master
Joined: Sep 2007
Posts: 7,604
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From: Belleville Il
Bottom line iridiums will run great at .040!!! When I pulled my (what I assume were the factory originals) gaps were all over the place.(running from low .060s to .080s) I used delco iridiums, and checked at the parts store book stating .040,no variation. checked all making sure they were .040 and it really woke her up. It was not running bad,, just ran better after! Shortly after I put my car in the Valvoline dyno display when the NHRA came to St.Louis. They did an initial 3 pull run then 5-2pull runs(total of 13 pulls) My car is bone stock except for a Black wing and Corsa Touring(stock H pipe).HP/Torque #s were #1-323051/324.76---#13-338.92/345.91. The print outs showed where the stock ECM was adjusting the air/fuel ratio as it "learned it was going to run WOT.(it was quite rich on the early pulls) Bottom line .040 will work,,do it and then take it out and run the wee wee out of it!! It will run better. I took it to test and tune that following Tuesday and capped the night off with a 13.08/110.23 on Goodyear runflats!! Enjoy!!
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
My point was missed too-A NASCAR engine running 500 miles at 9000 RPM will wear just as much as a street engine would at 30,000 miles averaging 2500 RPM-maybe even more--So for ME , whatever they say or use is best when it comes to things like plugs--If you like the plats or irridiums--go for it--just hope you can get them out after 50K miles !!
Burning Brakes
Joined: Mar 2005
Posts: 1,227
Likes: 15
St. Jude Donor '06
I agree its definitely best for performance...just not for longevity.
My original plugs were still in the car after 75000 miles. 7 of the 8 plugs lost their "pucks" and i had zero trouble removing any of them...
My original plugs were still in the car after 75000 miles. 7 of the 8 plugs lost their "pucks" and i had zero trouble removing any of them...
Last edited by Stealthy4; Aug 7, 2008 at 11:45 PM.
