Spark plug gap , what is really the best ?

Who knows what is really better? It was about a month ago that I bought new spark plugs and wires. I think when I first put them at .45 it felt better. But I don't clearly remember. Than I couldn't let the thought go that the book said .60 so I took them out and gapped them to .60  so now I'm thinking about it again and can't let the thought go. What should I gap them too ? Because honestly right now I don't feel some huge difference compared to the old ones. Maybe it's just me 

I doubt you would be able to feel any difference in such a subtle gap difference.

I know the 2002 manual recommended gap was set pretty wide; I think it was 0.060". It was later revised down to, I believe, 0.045". My situation is a little different than yours as I'm running regular NGK plugs in one heat range cooler due to the supercharger, but I run 0.045" gap.

So you think if I gap it to .45 it would just be in my mind a difference and not an actual difference? Ha. Why was it revised down ? Benefits , smoother , better mpg ? Thank you

brownprider07 said:

Why was it revised down ? Benefits , smoother , better mpg ? Thank you

Click to expand...

Borrowed from another forum.

<snip>
GM revised the plug design and gap specifications for all gen III engines mainly due to idle instability. Per TSB 30604060, iridium plugs gapped at .040" are the new recommended plugs.
</snip>

I would say the idle on the av I have isn't the greatest. So should I re gap them back to .45 ? Or maybe something in the middle ? Won't I lose mph or something ?

brownprider07 said:

I would say the idle on the av I have isn't the greatest. So should I re gap them back to .45 ? Or maybe something in the middle ? Won't I lose mph or something ?

Click to expand...

Here's the Actual TSB   And yes, the AC Delco iridiums will last 100,000 miles and you're over thinking this, on a stock motor with stock plugs this is probably the way to go.

Subject: Information on New Spark Plugs and Gapping #03-06-04-060 - (10/24/2003)



Models: 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.

.40 for me.

I have a 2004 Avalanche Z71 with 127k miles. I just spent a week from hell investigating P0300 codes after a weekend of modding. Only to find out it was my brand new Spark Plugs!

The owners manual said .04 all the part websites recommended .04. The plugs I pulled out .06! My truck did not like the .04's at all!

My advice go with the gap that you are currently running.

You can read more about my journey through hell here... Hopefully it can save you the $$, time and headache...

http://chevyavalanchefanclub.com/cafcna/index.php/topic,147504.0.html

My 03 was idling a bit funny with just over 100k on it.  The plugs/wires looked factory, so I decided to replace them.  The idle is way smoother, and my mileage went up just a tick (about 14 vs 13.5, lol).  I expected power to be better, and it seems fine on the flats, unloaded.  BUT on hills and loaded at all, it feels like I'm getting an incomplete burn, and it's just really bogged down compared to the factory plugs.

I'm thinking it's from me being cheap and short on cash, I bought the copper AC Delco's instead of the iridium.  But I'm also suspicious of the plug gap issue.  My originals were .06, and the new coppers were .04.  I noticed the diff, looked at this site, and saw the change in factory setting.

I know that Iridium tips should last longer, but should I see a huge power loss under loading running coppers?  I bought a new set of Iridiums with my bonus last week, also gapped to the new spec.  Who wants to place bets on wether it runs better?  I was tempted to re-gap them and just split the difference to .05, but don't want to damage the tips.

I probably should've just changed the wires only in the first place, they're usually the culprits anyway, at least in my previous experience...

zr2s10 said:

BUT on hills and loaded at all, it feels like I'm getting an incomplete burn, and it's just really bogged down compared to the factory plugs.

Click to expand...

I suspect clogged cats...

enoniam said:

I suspect clogged cats...

Click to expand...

Maybe if it weren't an instant change.  Right after I changed the plugs, I got this behavior.  Before it just had a rough idle, but plenty of power.  New plugs and wires gave me a smooth idle, but neutered the thing immediately.  I may not have been clear on that before, sorry.  Also, I have not put the new iridiums in yet, I guess I'm just trying to get opinions first, but I'll probably leave them as gapped

JVZL1 said:

The gapping can make a difference in performance the OME is not always optimal for your personal drive habits. Being you have your other set take you coppers and experiment with the gapping. I would have to check to see what gap I?m running at this time.
  If the copper plugs are a cross over for the iridium?s they should perform the same with the same gapping. 
The coppers will not last as long the purpose of iridium. With copper you would look at somewhere in the 30k range for changing.  I have ran both with no performance change, stick with the AC and all will be good. Have you cleaned your throttle body, MAF and with a 03 the fuel filter? Did you use anti-seize when installing? Run your AVY in the dark lift the hood to see if you are getting any spark flow from the wires or around the plugs. I have installed new plugs that were cracked that you could not see until they were ran.
Did you change where you purchase your fuel, do live an area where they change the percentage of Methanol after the install of plugs? Just some random thoughts.

Click to expand...

I"ll try changing the copper gap first, good idea.  I think I'll split the difference between old and new spec, and go with .05 to start.  Even if the gap does make a difference, I will still clean the MAF and throttle body.

I did not use anti-sieze when installing, but I think I'll put some on, to help with the conductivity.  The old ones looked pretty clean, but you never know.

I actually did crack one plug when I did the install.  I heard a little pop, but didn't feel anything on the ceramic, so I left it go at first.  It ran okay, but started to get an increasingly worse miss under light throttle.  Pulled that plug and it had lots of black lines on the ceramic, lol.  Replaced it, and that went away, but the poor power under loading/hills was still there.

They do change fuels around here, but it was mid-summer at my plug change, they typically change fuels here around March/April and then Oct/Nov, depending on the weather.  But I've also been through that with this truck, and have never noticed a difference.

I hope to do the work this weekend.  I have a wheel bearing on my car that needs changed first.  And with a 3 yr old and a 3 mo old, I haven't had much time to wrench, lol.  The 3 yr old, he's pretty self sufficient, but gets into everything.  And that 3 month old, man, she's so needy, lol.  My wife works evenings, so I'm Mr. Mom after work every day.

Is it the same for like a 2009?

anti-seize will not help conductivity it will do the opposite, use it sparingly.

Using copper plug is insane. 

You should use anti-seize, especially on aluminum heads but you only need a tiny bit, just a dab on one side is enough. With today?s 100,000 mile plug changes you need all the help you can get so they don?t seize up in the head. Also anti-seize acts as a lubricant and will increase torque you put on the plug, so don?t over tighten them, and too much can cause issues if you get it all over the ceramic insulator and boot.

Manufactures recommended plug gaps are probably the best for most users, if you?re having problems with misfires there?s probably something wrong and changing the gap from factory is not going to fix it.

If you want to play around with gaps then opening them up can help ignite the fuel better for a more complete burn and increase efficiency so you might see a fraction of a mpg on the highway. But there?s a tradeoff, the plugs will have to be cleaned, re-gapped or changed more often because as they wear the larger gap puts an increased load on the secondary ignition components and the wider gap may misfire at high RPM?s. If you put aftermarket coils on like MSD?s or DUI?s you can usually increase the gap safely because of the higher voltage output.


Closing the gap will fire more reliably at high RPM?s, better throttle response and last longer between changes. If you?re increasing the compression or adding a supercharger, turbo or N2O then you will almost always need to close the gap as recommended by the company who makes it.

Will you be able to measure the horsepower or mileage increase or decrease? Probably not unless you have access to some high tech measuring equipment or have your engine on a dyno and make multiple pulls experimenting with different gaps.

I put the MSD coils on my AV and felt like it idled smoother, pulled a little stronger. I haven?t been on any long trips so I can?t say if the mileage went up but it seems to have helped a little. I also left the gap at the factory 0.060.

GM says that setting the gap on platinum and iridium tipped spark plugs ends up scratching the precious metal coating on the tips.  Therefore, they recommend not attempting to change the gap at all.