AC Delco Iridium Spark plug gap...
07-23-2013, 06:43 PM
#1
Le Mans Master
Thread Starter
AC Delco Iridium Spark plug gap...
I'm installing new plugs in LS6 and need to check the new plugs for the proper gap.
What should it be?
Thanks!
What should it be?
Thanks!
07-23-2013, 08:29 PM
#3
Tech Contributor
They come pre-gapped from the factory. Do not attempt to gap them; the electrodes are easily damaged or broken!
07-24-2013, 08:25 AM
#4
Le Mans Master
That is correct !
07-24-2013, 08:31 AM
#5
Race Director
I would still verify the gap on the plugs prior to installation. Just as I check the resistance on my new plug wires prior to installation. If you find a plug off by more than .001 I would ask the store you purchased them from for a replacement, and then check it too.
07-24-2013, 05:43 PM
#6
Melting Slicks
I have never had a problem gapping iridium plugs. Use the correct tool and be careful of the electrode. No different than any other plug. I set mine to 0.055. Factory spec is 0.060 according to my service manual.
07-25-2013, 08:11 AM
#7
Safety Car
I bought my plugs via mail, and some, two I think, were not correct. Could have been shipping damage, but I don't think so.
Gapped them to the newer spec with no problem using a cheapie tool from the parts store. I did use a magnifying glass because of all the warnings of fragility of the electrodes. Didn't seem to occur any damage in gapping.
I assume because of the service interval they want the electrode faces new and square. I was worried the material would be very brittle. I didn't do a microscopic inspection, but feel the magnification was strong enough to settle any worries about damage. To my eye, I didn't need magnification for a damage check. !00, 000 miles from now, I will just gap with care.
I also assume the manufacturing tolerances are such that the small inconsistencies were considered immaterial, so don't bother to gap them. Indeed, the inconsistancies I found were small, well within the range between my old plugs at the old spec, and the new spec.
As advised by this forum, my idle cleaned up a bit with the closer gap. ,060 verses ,040 if I can recall.
Gapped them to the newer spec with no problem using a cheapie tool from the parts store. I did use a magnifying glass because of all the warnings of fragility of the electrodes. Didn't seem to occur any damage in gapping.
I assume because of the service interval they want the electrode faces new and square. I was worried the material would be very brittle. I didn't do a microscopic inspection, but feel the magnification was strong enough to settle any worries about damage. To my eye, I didn't need magnification for a damage check. !00, 000 miles from now, I will just gap with care.
I also assume the manufacturing tolerances are such that the small inconsistencies were considered immaterial, so don't bother to gap them. Indeed, the inconsistancies I found were small, well within the range between my old plugs at the old spec, and the new spec.
As advised by this forum, my idle cleaned up a bit with the closer gap. ,060 verses ,040 if I can recall.
07-25-2013, 09:25 AM
#8
07-26-2013, 07:45 AM
#10
Le Mans Master
but service bulletins after the service manual was written say .040
07-26-2013, 10:12 PM
#11
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Not sure why people are continuing to say there "service manual says" There Service manual also calls for a different plug the is not Iridium plug that has been in place for some time with the .040 gap. That is why they come mostly pre-gapped at .040.
Call any chevy dealer they will tell you .040 gap. ask evil twin he will tell you the same. My 2000 manual says .060 and a different plug. I run iridium with the gap of .040 per stated by many many many people and the ;ocal parts guy said the same.
Hope this clears up the spark plug issue, by the way they dont show TSB'S in the manuals or any recalls or changes to the process of our cars since the manuals were written years ago.
Call any chevy dealer they will tell you .040 gap. ask evil twin he will tell you the same. My 2000 manual says .060 and a different plug. I run iridium with the gap of .040 per stated by many many many people and the ;ocal parts guy said the same.
Hope this clears up the spark plug issue, by the way they dont show TSB'S in the manuals or any recalls or changes to the process of our cars since the manuals were written years ago.
07-27-2013, 08:54 AM
#12
Melting Slicks
Yes, there is a Service Bulletin stating 0.040". #03-06-04-060 in fact. I wouldn't fault anyone for following it - it won't steer you wrong.
I wanted more energy in my spark for a cleaner burn at the expense of replacing the plugs sooner. Since I only drive 1000 miles a year and my car is not FI I figure I'll never have to touch them again anyway. My LS6 runs very smooth at 0.055". Here's a little blurb from Wiki in case you don't know the trade offs of plug gap.
I wanted more energy in my spark for a cleaner burn at the expense of replacing the plugs sooner. Since I only drive 1000 miles a year and my car is not FI I figure I'll never have to touch them again anyway. My LS6 runs very smooth at 0.055". Here's a little blurb from Wiki in case you don't know the trade offs of plug gap.
The gap adjustment can be crucial to proper engine operation. A narrow gap may give too small and weak a spark to effectively ignite the fuel-air mixture, but the plug will almost always fire on each cycle. A gap that is too wide might prevent a spark from firing at all or may misfire at high speeds, but will usually have a spark that is strong for a clean burn. A spark which intermittently fails to ignite the fuel-air mixture may not be noticeable directly, but will show up as a reduction in the engine's power and fuel efficiency.
As a plug ages, and the metal of both the tip and hook erode, the gap will tend to widen; therefore experienced mechanics often set the gap on new plugs at the engine manufacturer's minimum recommended gap, rather than in the middle of the specified acceptable range, to ensure longer life between plug changes. On the other hand, since a larger gap gives a "hotter" or "fatter" spark and more reliable ignition of the fuel-air mixture, and since a new plug with sharp edges on the central electrode will spark more reliably than an older, eroded plug, experienced mechanics also realize that the maximum gap specified by the engine manufacturer is the largest which will spark reliably even with old plugs and will in fact be a bit narrower than necessary to ensure sparking with new plugs; therefore, it is possible to set the plugs to an extremely wide gap for more reliable ignition in high performance applications, at the cost of having to replace or re-gap the plugs more frequently, as soon as the tip begins to erode.
As a plug ages, and the metal of both the tip and hook erode, the gap will tend to widen; therefore experienced mechanics often set the gap on new plugs at the engine manufacturer's minimum recommended gap, rather than in the middle of the specified acceptable range, to ensure longer life between plug changes. On the other hand, since a larger gap gives a "hotter" or "fatter" spark and more reliable ignition of the fuel-air mixture, and since a new plug with sharp edges on the central electrode will spark more reliably than an older, eroded plug, experienced mechanics also realize that the maximum gap specified by the engine manufacturer is the largest which will spark reliably even with old plugs and will in fact be a bit narrower than necessary to ensure sparking with new plugs; therefore, it is possible to set the plugs to an extremely wide gap for more reliable ignition in high performance applications, at the cost of having to replace or re-gap the plugs more frequently, as soon as the tip begins to erode.
07-27-2013, 08:38 PM
#15
Tech Contributor
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CI 6,7,8,9,11 Vet
St. Jude Donor '08
My buddy Mike called me and I had to chime in on this subject:
Here is that bulletin that was discussed (see below)
GM does stuff either to save money OR to increase or extend serviceability or to correct a known issue.
Ive never seen anything changed that has ever increased HP..
If you increase plug gap, sure; you get more spark. You also chance getting more misfire.
Our secondary ignition system is pretty dog gone good as an OEM system. Little or nothing is ever gained in changing plugs, wires or coils.
Plug gap changes may or may not help or hurt performance depending on your engine and whats been done to it mod wise.
I seriously doubt that you will see any seat of the pants improvement but, over a period of time and miles, you may see either a gain or even a loss in fuel efficiency. The wider the gap, the more that you will have to service the plug to keep that gap from getting too large. Once the plug starts to get over 0.070, it starts to have negative effects on idle quality and performance. If there is ANYTHING wrong , say in a spark plug wire or a coil, a wide gap will surely cause a misfire.
Like I discussed with Mike; If you are concerned that plug gap will make a difference, you should also be looking at spark plug indexing.
Increase the gap and see how it runs and performs. Its not like something that you can not easily change if you don't like the results and its not going to hurt anything.
This all goes out the window if you are running forced induction as the type of plug and gap can and will make a difference.
TSB
Document ID# 1396703
--------------------------------------------------------------------------------
Information on New Spark Plugs and Gapping #03-06-04-060 - (Oct 24, 2003)
Information on New Spark Plugs and Gapping
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 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, 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 1.01mm (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.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
© Copyright General Motors Corporation. All Rights Reserved.
--------------------------------------------------------------------------------
Document ID# 1396703
07-28-2013, 08:32 AM
#17
Melting Slicks
I agree with what Bill mentioned above. You're not really going to see a difference. My own personal feeling on the TSB is GM is looking for longer plug life. Switch to Iridium with a tighter gap and your plugs will likely outlast the rest of the engine. Iridium is very resistant to erosion, it conducts slightly better than platinum but it is very similar to platinum atomically. It's the erosion resistance that makes it perfect for spark plugs.
07-29-2013, 10:29 AM
#20