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AC Delco plugs


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Poll: Which plugs do you run?

Which plugs do you run?

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#16 timh975

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Posted 02 May 2006 - 01:10 AM

2002 2500hd,6.0L. i changed to the ac-delco #41-983, at .040" gap. i am seeing a 2 mpg drop in my milage. any body else? this plug is at .040" gap, when the oem plugs were at .060" gap.
thanks.

<{POST_SNAPBACK}>


Hey REBOP, I noticed a slight drop in MPG's also. I recently replaced the plugs in my 6.0 with the iridium plugs. Even though the sticker under the hood says .060" gap, the dealer told me to leave the new plugs gapped at .040", it will run fine and will also run cooler. My truck ran just fine with original plugs, now I'm wondering if I should've just left them alone.
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#17 REBOP

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Posted 02 May 2006 - 07:55 AM

2002 2500hd,6.0L. i changed to the ac-delco #41-983, at .040" gap. i am seeing a 2 mpg drop in my milage. any body else? this plug is at .040" gap, when the oem plugs were at .060" gap.
thanks.

<{POST_SNAPBACK}>


Hey REBOP, I noticed a slight drop in MPG's also. I recently replaced the plugs in my 6.0 with the iridium plugs. Even though the sticker under the hood says .060" gap, the dealer told me to leave the new plugs gapped at .040", it will run fine and will also run cooler. My truck ran just fine with original plugs, now I'm wondering if I should've just left them alone.

<{POST_SNAPBACK}>





i went back to the autolite double platium at .060" gap. my milage is back to normal. check this out :
http://www.sparkplugs.com/default.asp


thx - rebop.

#18 Haulin' 8.1

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Posted 10 June 2006 - 07:18 AM

I didn't just pull this out of my !@$. I've been tuning engines for geeze longer than I care to remember and most who know me think I'm one of the best.

The wider your plug gap is the leaner the fuel mixture can be.  I run my Champion Double platinum plugs wider than stock for better milage.  Todays ignitions will jump the gaps way beyond reason, I know I do peoples tune ups, so an extra 0.005 isn't a problem if you change plugs every 50K but it sure helps the mileage.  Don't try it with a supercharger or NO2 though.

Vernon

<{POST_SNAPBACK}>


2001 Siverado HD 2500 SBCC in Black
GM Vortec 8100, Allison, 3.73, 4X4
Mods: Goodmark SS cowl hood, Ranch Hand bumpers, black toolbox, custom bed cover, full tint, Volant with home made ram air, BBK 80mm TB, Granetelli MAF, Marine Injectors, Hypertech, Champion RS12YC plugs, Magnaflow 3" dual in X-path dual out muffler and tail pipes, Fuzion XTi 265's, Velvet Rides, Pioneer 10" subs, amps, you know the usual stuff.
Coming soon: 4.56 gears, Autorotor supercharger by Whipple with Duramax intercooler, and GM HP3 cylinder heads.
If you've modded your 8.1's timing and run hard try Champion RS12YC plugs gapped at 0.055". Less knock, more power. Yes you have to change them more often (25K), but this is a performance mod. Besides they're cheap and easy to do.

Yea though I drive the the valley of the shadow of Diesel,
I will fear no turbo;
For your horsepower art with me;
Your bore and stroke, they comfort me.

#19 Steady Eddie

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Posted 10 June 2006 - 11:52 AM

:chevy:
Didn't Delphi file a Chapter 11? Aren't Denso Iridiums now
OEM installed in all 8.1s? Isn't there a TSB on plug gaps?
(I'm thinking of one for the Corvette and others). Are the
AC-Delco Iridiums made by NGK?

Steady Eddie :)

Edited by Steady Eddie, 26 June 2006 - 11:02 PM.

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#20 duramaxHD

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Posted 12 July 2006 - 06:12 PM

I dunno, whichever ones my truck came with...






:rant:
2005 silverado cc/sb 4x4 LT
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not the original engine, and a buncha other stuff too.

#21 Haulin' 8.1

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Posted 12 July 2006 - 10:23 PM

Shirley, you can't be serious.

Vernon
2001 Siverado HD 2500 SBCC in Black
GM Vortec 8100, Allison, 3.73, 4X4
Mods: Goodmark SS cowl hood, Ranch Hand bumpers, black toolbox, custom bed cover, full tint, Volant with home made ram air, BBK 80mm TB, Granetelli MAF, Marine Injectors, Hypertech, Champion RS12YC plugs, Magnaflow 3" dual in X-path dual out muffler and tail pipes, Fuzion XTi 265's, Velvet Rides, Pioneer 10" subs, amps, you know the usual stuff.
Coming soon: 4.56 gears, Autorotor supercharger by Whipple with Duramax intercooler, and GM HP3 cylinder heads.
If you've modded your 8.1's timing and run hard try Champion RS12YC plugs gapped at 0.055". Less knock, more power. Yes you have to change them more often (25K), but this is a performance mod. Besides they're cheap and easy to do.

Yea though I drive the the valley of the shadow of Diesel,
I will fear no turbo;
For your horsepower art with me;
Your bore and stroke, they comfort me.

#22 kraig

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Posted 27 November 2006 - 09:40 PM

My 01 6.0 has 93,000 and I changed my plugs. They were the factory parts, and they were worn...BAD. Five gaps were huge, .80-.85. No foolin. Put the A/C Delco plugs back in, which have a NGK number also, just like the ones that came out. The computer and the catalog said do not change the gap which is pre set to .40 but yes the underhood sticker says .60...go finger. Seems like it does not idle as smooth, it does have a little more poop and gets about 15 more miles out of the first half of the fuel tank on the highway. I get on it too much to notice a difference in town. Jus my .02. :rolleyes:

#23 MS3DALE

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Posted 27 November 2006 - 11:12 PM

Heres the bulletin on the spark plug replacement and gap....


Document ID# 1396703

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.


Document ID# 1396703

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#24 Black02Silverado

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Posted 22 February 2007 - 12:48 PM

Heres the bulletin on the spark plug replacement and gap....


Document ID# 1396703

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



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.




Document ID# 1396703



Interesting. It was suggested to me by the individual that does my oil analysis to do this exact thing, get the Iridiums and gap them at 0.040. He mainly instructed this to help improve my economy.
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#25 Billdog350

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Posted 22 February 2007 - 02:59 PM

I pulled a set of what looked like origional DELCO plugs from my truck after 130k mi. Some of the platinum tips had worn off! The plugs had NGK AND DELCO written on them (I can take pics if people don't believe me). They were in my 2003 6.0l Lq4.

I threw some iridiums in there and it runs great.

#26 dco111

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Posted 19 March 2007 - 11:52 AM

Haulin8.1 you refer to running champion plug and gapping them to 40 and changing them every 25,000 miles. Will this work for pulling, I have a 03 3500 with the 8.1 and all I do is pull with it. Every body talks about making them run faster but few talk about pulling. Thank you.

#27 Haulin' 8.1

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Posted 29 May 2007 - 07:25 PM

Haulin8.1 you refer to running champion plug and gapping them to 40 and changing them every 25,000 miles. Will this work for pulling, I have a 03 3500 with the 8.1 and all I do is pull with it. Every body talks about making them run faster but few talk about pulling. Thank you.


Hey I don't read this post a lot. But yeah they'll work fine in any 8.1 that's used for increased performance. They're basically a normal 8.1 plug that's one step colder than stock. The copper core retains less heat than the exotics so it's good for long period WOT detonation resistance. The smaller gap is for reduced WOT misfiring. Even though the copper is a good cool electrod it wears away faster than the other metals so about 25K miles would be my limit. The good thing is that these ignition coils are so strong and the smaller gap take a while to wear past limits so you'll probably not have any issues at 25K anyways.

Vernon
2001 Siverado HD 2500 SBCC in Black
GM Vortec 8100, Allison, 3.73, 4X4
Mods: Goodmark SS cowl hood, Ranch Hand bumpers, black toolbox, custom bed cover, full tint, Volant with home made ram air, BBK 80mm TB, Granetelli MAF, Marine Injectors, Hypertech, Champion RS12YC plugs, Magnaflow 3" dual in X-path dual out muffler and tail pipes, Fuzion XTi 265's, Velvet Rides, Pioneer 10" subs, amps, you know the usual stuff.
Coming soon: 4.56 gears, Autorotor supercharger by Whipple with Duramax intercooler, and GM HP3 cylinder heads.
If you've modded your 8.1's timing and run hard try Champion RS12YC plugs gapped at 0.055". Less knock, more power. Yes you have to change them more often (25K), but this is a performance mod. Besides they're cheap and easy to do.

Yea though I drive the the valley of the shadow of Diesel,
I will fear no turbo;
For your horsepower art with me;
Your bore and stroke, they comfort me.

#28 Waterfowlhunter

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Posted 28 July 2007 - 02:00 PM

I had the same white carbon buildup on my factory plugs after 40,000 miles and was told by the dealer that this is due to running 87 octane gasoline. I have now been running 89 and I can tell a difference. This 8.1L engine was rebuilt at 20,000 due to the oil pump bypass spring failing and killing the engine. They replaced only one plug at that time and it was an ac delco but the remaining 7 were Denso 5071 double Platinum. All gapped at .060. I replaced them all with Denso Iridium 5325 at .060 and it ran real bad so I dropped them to .050 and it ran great again but I also replaced 2 wires at that time with OEM wires. I have since had to replace a failed camshaft position sensor. Should I go back and gap the plugs to .060 again or leave them at .050?

Is there a performance plug wire for these engines?

#29 Haulin' 8.1

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Posted 31 July 2007 - 06:35 AM

Leave them at 0.50", it works doesn't it? Opening it up will only slightly improve part throttle emmissions at a great reduction in heavy throttle power. There are wires that are built stronger and have thicker insulation but any gains in power will be so small they aren't worth the expence. The OEM and built to OEM specs wire sets have a solid core so conductivity is very good and long lasting. Nobody uses carbon core wires in this day and age yet many think wires are still a first upgrade.

Vernon
2001 Siverado HD 2500 SBCC in Black
GM Vortec 8100, Allison, 3.73, 4X4
Mods: Goodmark SS cowl hood, Ranch Hand bumpers, black toolbox, custom bed cover, full tint, Volant with home made ram air, BBK 80mm TB, Granetelli MAF, Marine Injectors, Hypertech, Champion RS12YC plugs, Magnaflow 3" dual in X-path dual out muffler and tail pipes, Fuzion XTi 265's, Velvet Rides, Pioneer 10" subs, amps, you know the usual stuff.
Coming soon: 4.56 gears, Autorotor supercharger by Whipple with Duramax intercooler, and GM HP3 cylinder heads.
If you've modded your 8.1's timing and run hard try Champion RS12YC plugs gapped at 0.055". Less knock, more power. Yes you have to change them more often (25K), but this is a performance mod. Besides they're cheap and easy to do.

Yea though I drive the the valley of the shadow of Diesel,
I will fear no turbo;
For your horsepower art with me;
Your bore and stroke, they comfort me.

#30 07vmaxslt

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Posted 29 August 2007 - 09:18 AM

Rebop,
what does the sticker under the hood call for plug gap? Use that. (my guess is they should be .060) Remember, you have to gap ALL plugs, especially when new.

What if the spark plug box tells you not to? :cheers:

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