2003 Suburban 5.3L - Plug Gap - Conflicting Information

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I purchased ACDELCO 41962 GM Original Equipment; Double Platinum Plugs from Rock Auto for my 2003 Suburban 1500 Vortec 5.3L.
Manual says plug gap is .060. Dealer service department says plug gap is .060.
All the plug options I see on Rock auto, say to gap at .040, including the plugs I ordered.
Which is it?
Dealer service department says there is no TSB regarding plug gap.
 
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I would say that .060 is the winner. From what I understand, the gaps on LL platinum plugs are not adjustable. At least without risking damage to the platinum coatings. I'd be interested to measure the gaps (VERY CAREFULLY) on the plugs themselves. High probability that the listing is incorrect, and the plugs are gapped correctly.
 
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Spark Plug








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Spark Plug

Double Platinum

Part# 41-962 - ACDelco
Part# 19299585 - GM





Per Veh: 8

Years: 2000-2010

Gap 0.040 (in)

OE; GAP .040
VIN: T, Engine: LM7
VIN: Z, Engine: L59





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Spark Plug

Conventional

Part# R44LTSM - ACDelco
Part# 19354418 - GM





Per Veh: 8

Years: 2003-2005

Gap .040






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I would say that .060 is the winner. From what I understand, the gaps on LL platinum plugs are not adjustable. At least without risking damage to the platinum coatings. I'd be interested to measure the gaps (VERY CAREFULLY) on the plugs themselves. High probability that the listing is incorrect, and the plugs are gapped correctly.
Platinum, double platinum, iridium, and ruthenium plugs are adjustable. The only ones that I know that specifically say not to adjust are Bosch finewires and multi-strap designs like E3's

As per NGK: "If adjusting the gap on fine wire or precious metal plugs such as platinum or iridium, be very careful not to apply any pressure or prying force to the fine wire center electrode or insulator as they can be damaged. The gap should be adjusted by only moving the ground electrode."
 
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Platinum, double platinum, iridium, and ruthenium plugs are adjustable. The only ones that I know that specifically say not to adjust are Bosch finewires and multi-strap designs like E3's

As per NGK: "If adjusting the gap on fine wire or precious metal plugs such as platinum or iridium, be very careful not to apply any pressure or prying force to the fine wire center electrode or insulator as they can be damaged. The gap should be adjusted by only moving the ground electrode."
Huh, no **** huh.. I had a friend who gapped his NGK plats, and he ruined them. Multiple mis fires after 2k miles. I take it he used waaay to much force then.
 
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Huh, no **** huh.. I had a friend who gapped his NGK plats, and he ruined them. Multiple mis fires after 2k miles. I take it he used waaay to much force then.
lol you can't be belligerent with them. I've gapped NGK's, Autolite, and ACDelco platinums without issue but I had a buddy have a ground strap break off a plug in his Focus RS that took a valve with it
 
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There's been bickering about the plug gap in this application for over 10 years, based on what I see online.

Use the gap the sticker under the hood says. I'll bet it says 0.060". Since the dealer says there's no TSB updating the gap, stick with 0.060.

Going with too narrow a gap risks "shrouding" the spark so the fuel-air mixture doesn't ignite and burn properly, I would think.
 

D60

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GM "retroactively" declared these trucks should use Iridium and I thought that's where the discrepancy comes in.

The gap on the vehicle will be for what it left the factory with (double plat maybe??) but today's specs on paper would assume Iridium because that's the "new standard"

Am I wrong? Calling the GMT800 experts.....
 
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There is a TSB "Bulletin No.: 03-06-04-060B" that addresses this, .040" gap is correct for Iridium Plugs installed in LSx engines that originally had Platinum Plugs gapped at .060".

D60 is correct, In GM's eye's....Iridium is what you should run in ALL 1997 & up LSx engines. Delco# 41-110 is the latest P/N that your '03 calls for.

There's likely another engine that stuck with the same Platinum Plugs (or a cross reference to) that your engine originally specified & that's where the confusion comes from.
I know some HD 5.7L & 8.1L still call for the 41-962 gapped at .060"
 
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My Iridium Original AC Delco plugs from my LS3 after 75,000 miles. Gaps are HUGE on most. Car ran fine, mileage great..no misfire codes. Seems like the system could fire .040 - .060 without issue.
4768FA0F-D36E-4D6D-B3FC-F1B66613A88B.jpeg
 

Fitz98

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There is a TSB "Bulletin No.: 03-06-04-060B" that addresses this, .040" gap is correct for Iridium Plugs installed in LSx engines that originally had Platinum Plugs gapped at .060".

D60 is correct, In GM's eye's....Iridium is what you should run in ALL 1997 & up LSx engines. Delco# 41-110 is the latest P/N that your '03 calls for.

There's likely another engine that stuck with the same Platinum Plugs (or a cross reference to) that your engine originally specified & that's where the confusion comes from.
I know some HD 5.7L & 8.1L still call for the 41-962 gapped at .060"
Mine is the L59. Would I be wasting my time installing the 41-962 double platinum gapped at .060, instead of using the Iridium. I got these, because they are the ones that came with my truck when I bought it and I thought the OE spec would be a good target for replacement.
 
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As you already have them. Run them after you re-gap them to .060"!! I'm sure there are videos on how to gap the plugs without damaging them. (don't put the gapper between the electrode & ground strap!)
 
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Mine is the L59. Would I be wasting my time installing the 41-962 double platinum gapped at .060, instead of using the Iridium. I got these, because they are the ones that came with my truck when I bought it and I thought the OE spec would be a good target for replacement.
Did you ever get your rear end fixed ? You had a whine or something ?
 

Fitz98

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Resurrecting this old thread. Funny, I am just now getting around to doing my plug and wire job.
Everything I am seeing says .040, the plugs are pre-gapped at .040, the RA and other websites say .040.
The new 41-962 plugs I got from RA are pre-gapped at .040
With tons of research and looking at TSB's it seems like the only discussion regarding gap change from .060 to .040 is regarding the use of Iridium plugs, but that does not explain why the platinums are pre-gapped to .040

I pulled an original plug (at least what was in there when I bought it at 66k miles. I now have 204k miles on it.)
The plug I pulled is NGK PZTR5A-15 AC Delco 12567759 which appears to be a platinum plug.
With my 138k miles, the original plug that I pulled has a gap of .062
I am wondering if these old plugs were originally installed with the .040 gap and they have worn to .062, or is it possible that after more than 138k miles that they have only worn .002 if they were previously installed at .060?

2022-08-02 23.57.28.jpg


I am on the fence here about what to do. I would be fine using the double platinums if I can get the gap set with confidence, since it seems like my original platinums have served me well for at least 138k miles.
I can get 41-110 on Amazon for 7.00 with free shipping (but amazon fitments says it does not fit my Suburban though) and know the gap is supposed to be .040, but that seems like a waste.

2022-08-02 23.57.28.jpg
 
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D60

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^^^^based solely on everything here from @clinebarger I'd run .060"

Honestly, I'm not sure you'd see much difference in performance with either setting.

If you REALLY wanna straddle the fence set 'em at .050" :D
 

Fitz98

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Chevy service department says they take them out of the box and install them as they are pre-gapped...which is .040.
NGK said:
"The tip metal does not matter on the gap all plugs (Iridium, Platinum, Nickel) require .040” gap for that engine."
Waiting to hear what AC Delco says. They were sending me to the dealer/service vendors with their last response.

Clinebarger always offers good knowledgeable advice and seems very well-respected in this forum. He has helped me on many occasions, so I am tempted to just take that advice and run with it.
I wish there was TSB documentation somewhere that would have stated it...there is more stating it is .040 than there is supporting the original .060
One reassuring thing is that my truck seems to run good with the .062 that they are at now. Occasional, random pinging when coming off idle, but I think that has more to do with the bad knock sensors...I don't know what else will need to break to force me to remove the intake to change these.

When bending the ground strap back .020 to increase gap, does it matter if the tip and the little dot on the ground electrode are not directly opposite. It seems like bending the strap back pulls those 2 points out of direct opposing alignment
Thought about the .050 thing, but I am a data guy. I have an engineer mentality, which gives me a lot of stress in the simple every day things...like spark plugs.
 
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I did the plugs in my 2002 Tahoe 5.3L at 250k miles (currently at 280k miles). I used NGK TR55IX (PN: 7164) gapped at .058-.060". No issues with it. It starts easy and drives smooth, that includes while towing. I chose to ignore the TSB.

Most ACDelco plugs are made by NGK.
 
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Fitz98

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I did the plugs in my 2002 Tahoe 5.3L at 250k miles (currently at 280k miles). I used NGK TR55IX (PN: 7164) gapped at .058-.060". No issues with it. It starts easy and drives smooth, that includes while towing. I chose to ignore the TSB.

Most ACDelco plugs are made by NGK.
That is reassuring.
These engines and vehicles are amazing. you have 280k , I have 204k and still runs like new. Need to so some rear end work soon though.
Easy to work on everything on this. I haven't encountered anything that I would say was hard to get to yet. I have a 98 Expedition as well with 250k, but it is nightmare to work on anything on that thing and it lacks power for towing.
I didn't used to be brand loyal, but having worked on Expedition and Suburban now, my next one will be a similar GM for sure. They have their problems like anything else, but I like the serviceability, longevity and power Just need something a little more than what I got for towing..maybe the 2500...sorry getting off topic here.
 

Fitz98

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This is what I was referring to. When I bend the ground strap to make .060, the small dot on the ground electrode does not line up with the center electrode. Is this a problem?
2022-08-03 17.20.25-2.jpg


So far so good. All the plugs are loose without damage to the threads At this point with 204 k miles, that was a lot better than I expected.
 
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