spark plug gap

[lawood]

i am changing spark plugs in my 2000 ls1, the parts store gave me bosch platinum plugs, the gap is .040 does anybody know it that would be correct for this plug or should it be closer to .050? thanks

[ggino85]

i know the stockers are .060, i just checked the ones that im taking out of my car. the ngktr55's im putting in are at like .057 or .055 depending on how you read the spark plug gap measure thingy im not sure if the bosch's are the same or not.

[Mr. Luos]

My first recommendation would be to return those Bosch piles of junk.

Second...pick up NGK TR55's or the Autolite version.

Third...gap for a stock'ish' LS1 should be .054-.055"

[lawood]

My first recommendation would be to return those Bosch piles of junk.

Second...pick up NGK TR55's or the Autolite version.

Third...gap for a stock'ish' LS1 should be .054-.055"

excellent advice mr. luos, unfortunatly i had to find out the hard way and installed the bosch junk!! they will be coming back out. car is worse than with the wore out factory plugs that had a .075 gap!

[WS6ICK]

NGK TR55 gapped at .055 FTW!

[SteveC]

The above post is correct, the NGK plugs (for NA motor) are gapped @ .055.

The stock plugs are gapped @ .060 from the factory (if they get it right).

Keep in mind that the NGK plugs mentioned are COPPER tipped, which means they will only last 30K maximum. I use them on my garage queen (Sara) a 2001 Z28 that has 23K original miles.

SteveC

[david68]

Hmm...I'm getting confused now. I thought GM changed their gap recommedation for the LS1 from .06 to .04 some time ago? Something to do with achieving an improved idle? In support of this, I note that NGK list their LS1 plugs (TR55, TR55IX, TR55GP) as having an oe gap of 0.044.

Could do with having this clarified as I've just ordered a set of new plugs (AC Delco iridium) and want to make sure they are gapped as they should be before installing them.

[axxdet]

just changed mine with AC Delco iridium gaped at 55 the ones I pulled out were prop stock (only 39k on car) and gaped at closer to 60 and it looked like the tips were wore down a bit making me think thats why the gap was closer to 60....but it starts smoother/idles better

[2001NBMZ28]

GM did change the gap for some reason - I saw the change on NGK's website last year and sent NGK an email. I posted a little about it in this thread: www.ls1.com/forums/showthread.php?t=49408

[sunsetorangess]

Heres a little info on why they changed it and what it effected.
J

Bulletin No.: 03-06-04-060A

Date: February 12, 2007

INFORMATION

Subject:
Information on New Spark Plugs and Gapping

Models:
2004 Buick Rainier
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 GMC Sierra
2000-2004 GMC Yukon, Yukon XL
2001-2004 GMC Yukon Denali, Yukon XL Denali
2002-2004 GMC Sierra Denali
2003-2004 GMC 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, LS1, L56, LQ9, LQ4)

Attention: Please disregard the Set Gap Per Vehicle Specification statement on the side of an ACDelco(R) Iridium Spark Plug Box. The statement will be removed from the boxes in the future.

Supercede:

This bulletin is being revised to bring attention to the Set Gap Per Vehicle Specification on the ACDelco(R) Iridium Spark Plug Boxes. Please discard Corporate Bulletin Number 03-06-04-060 (Section 06 - Engine/Propulsion System).

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 in) 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.

[axxdet]

so .055 is to much?..

[lawood]

my tips were completly gone on all plugs and the gap was .075 they were the delco factory plugs i believe

[Mr. Luos]

so .055 is to much?..

Not for an NGK copper tip plug.

[david68]

Well I just pulled out one of the plugs fitted to my 2001 Z28 with 41k miles, to take a look ,and it's an ACDelco 41-985 iridium plug. Looks in very good condition with no apparent tip wear and a healthy light tan colour to it. I haven't got a tool to measure the gap, but it looks to be exactly the same as the new set of 41-985's that I have just received. Laying the plug against a tape measure the gap looks to be dead on 1mm, which I believe is 0.040".

Given that the 41-985's with the 0.040 gap were only released in 2007 (as per Bulletin No.: 03-06-04-060A) these must be fairly new plugs, so looks like I've wasted my time buying a new set. Guess I should have checked first

[rbob93]

Exotic metal plugs center electrode is much smaller requiring lower voltage to fire.
Our engines were designed for larger gaps due to the lower emissions they produce with our ignition systems. (Our systems can fire the large gap)
Larger gaps (provided they have sufficient voltage) produce a better chance for more complete burn thus reducing emissions. Because of the more complete burn, they consequently produce more power.
Exotic metal plugs were designed for applications where plug changes are costly time & consuming.
They work fine in our systems & reduce plug change intervals.
The harder metals wear slower than the nickle alloys found in common plugs producing an easy to fire, long wearing plug, that still produces a good burn & low emissions.