Spark Plug Gap Confusion

[J.B.R.]

I have searched and read alot about the plug gap question. Form what my take is.

GM has changed its .060 gap requirement to .040

They now beleive the new higher compression engines need less gap.

Now this goes for all spark plugs, standard, copper, iridium and platium. true or false?

Now my confussion. I have a 99 Denali with the 5.7l engine, is this considered a high compression engine and falls under the gap change rule? I read the list of trucks affected but did not see 99 Yukon Denali 5.7l listed.

 

Can someone set me straight.

[C & A s Dad]

Joe, your truck does not fall into this category. If you use AC Plugs, you will use a 41-932 and it is pre-gapped at .060 and the book recommends .060. If you use NGK, you have 4 plug choices, 3951 V Power, 3403 Platinum, 7164 Iridium or 7862 Laser Plat & Iridium and they are all gapped at .060.

 

Hope this helps

[J.B.R.]

Joe, your truck does not fall into this category. If you use AC Plugs, you will use a 41-932 and it is pre-gapped at .060 and the book recommends .060. If you use NGK, you have 4 plug choices, 3951 V Power, 3403 Platinum, 7164 Iridium or 7862 Laser Plat & Iridium and they are all gapped at .060.

 

Hope this helps

 

 

Thank You for the reply: I did see the NGK TR55 v power listed for my engine yet is showing .044 gap, and all orters Champ, AC, ect. are listed at .060 gap. So I guess Im still a little confussed.

[C & A s Dad]

The info I pulled on NGK came right from their most current catalog. The 3951 is the TR55 as you mentioned and their catalog list the gap at .060.

 

Where did you find the TR 55 to be gapped at .044?

[J.B.R.]

 

www.rockauto.com and just follow your specific car.

[HyperBuzzin]

Hmm, all the NGK's it shows for my truck say .044 too? But everything else says .060.

[C & A s Dad]

Joe, I took a look at the catalog on the link you provided. I also checked NGK's website and their electronic catalog. The crazy thing is NGK's elect catalog on their website shows a .044 gap and their 2006 paper catalog, which I have in my hand shows .060. I also looked this application up using our (CARQUEST) electronic catalog and it agrees with the NGK paper catalog and shows .060.

 

I am going to contact NGK and see why they have a discrepency between their paper cat and their e cat on their website.

 

I will let you know what I get back.

[svensk]

That would be cool Trey. I'm looking at going with those NGK's your running.

[C & A s Dad]

I contacted them yesterday but have not heard back yet. If I do not hear from them, I will contact my local Rep and let him see if he can get us an answer.

[J.B.R.]

Trey: Thanks for all your work on this, and if you do learn something please let us know. It looks as if the confussion continues.

[C & A s Dad]

I received the answer from NGK and was even able to speak with one of the engineers. He said that when GM changed suppliers and left NGK they changed the gap from .060 to .040. NGK has already adjusted their 7862 laser plat plug to .044 but the 3951 (TR55) is still at .060. He said they will likely be adjusting it to the OE recommendation also. For now, you could buy a set of 7862s that were mfgd at .060 or if they were recently mfgd they could be at .044. Of course these fine wire plugs such as the 7862 should not have the gapped reset as they are easily damaged.

 

He said they have never received any negative info from the plugs being set at .060 but are trying to adjust to the OE recommendation.

 

Bottom line, they seem to be confused also. I would run them at .060 and leave it alone unless of course you buy the 7862s and get some of the newer ones, and they are already set at .044, then leave them alone.

Not sure this helped but it is what I was able to get.

[J.B.R.]

Great work. I guess this explains the one thread I read where someone bought the NGK Plat. and some were at .060 and some were .040 (+,-). So it looks like even the TR55 will be at .044 soon. For some reason maybe back in my childhood days I always beleived that plug gap was important, It seems now it was not as important as I thought.

[fhelvie]

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

 

Date: February 12, 2007

 

Subject: Information on New Spark Plugs and Gapping

 

It states to ignore the instructions on the AC Delco Iridium spark plug box which says to "set gap to vehicle specs". The new Delco Iridium plugs have a different tip design and are pre-gapped at the factory to .040". Suspect this will affect similar plugs from other manufacturers.

[svensk]

BTW- I'm running the NGK TR-55 copper plugs (vette ones), and I left the stock .06 gap they came with. The 5.3 has never ran so smooth. The wait4me really seemed to of taken advantage of it and truck continues to get a bit faster.

[BigJayDogg3]

Svensk was there any kind of "seat of you pants" power pickup after you switched plugs, or is the truck more linear in power delivery? In other words can you describe what you mean when you say the truck is smoother?