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Spark plug question

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Jeff Dodson, Dec 8, 2013.

  1. Jeff Dodson

    Jeff Dodson Member

    My 99 Sierra 5.3 when to removed the original spark plugsAnyone at 250k, I took an original to O'Rielly's and got the replacements. Anyway the spec sticker under the hood said spark plug gap at .60, the replacements are pregapped at .40.... That's what their computer said.... I just stuck them in. Should I have re gapped them to .60 or was it fine to leave them at .40..... Runs fine
  2. BurbanMan

    BurbanMan Member

    gap them at .60 if that is what the hood says to do. "Runs fine" should become "runs great"
  3. 99'HEARTBEAT

    99'HEARTBEAT Moderator Staff Member Platinum Contributor 1000 Posts


    Jeff if you bought A/C Delco Iridium Tip Spark Plugs......do not attempted to Re-Gap them,

    Here's a GM Service Bulletin that goes into detail Regarding Gaping of the Iridium Plugs,......if you bought Platinum Plugs, then as the sticker under the hood said Spark Plug Gap at 0.60....


    --------------------------------------------------------------------------------
    Service Information 2000 Chevrolet Chevy K Silverado - 4WD | Sierra, Silverado, Suburban, Tahoe, Yukon (VIN C/K) Service Manual | Document ID: 1903277
    #03-06-04-060A: Information on New Spark Plugs and Gaping - (Feb 12, 2007)



    Subject: Information on New Spark Plugs and Gaping


    Models: 2004 Buick Rainier

    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)


    Attention: Please disregard the Set Gap Per Vehicle Specification statement on the side of an ACDelco® Iridium Spark Plug Box. The statement will be removed from the boxes in the future.

    • 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 Gaped to 1.01 mm (0.040 in) when the Spark Plug is Made.


    ***Notice: 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 Gaped Should Not Be Used.



    EDIT:....I would also mention, that the Spark Plug Fastener Tightening Spec's. are 11 lb ft and also make sure to use some.....Anti-Seize Compound on your Spark Plugs, is particularly advisable with Engine Head's made of Aluminum, and use Dielectric Grease, Use your finger to spread the Dielectric Grease around the Ceramic Portion of the Spark Plug. This will help maintain a dry environment for the Spark Plug to Wire connection. The Grease will also make Re-Installation of the Plug Wires easier.


    EDIT:.....GM has Changed the Part Number for the Iridium Tip Spark Plugs, the New Part Number is 41-110
    Last edited: Jan 22, 2014
  4. BurbanMan

    BurbanMan Member

    I didn't think about asking what kind of tip they have... *palm to forehead*
  5. fugitive

    fugitive New Member

    Is the gap realy .600 or is it .060??????????????
  6. Jeff Dodson

    Jeff Dodson Member

    Well being that .600 is over half an inch, pretty sure I meant .060.... But thanks, it is the iridium plugs, that is what O'Rielly's books called for. Thanks again
  7. 99'HEARTBEAT

    99'HEARTBEAT Moderator Staff Member Platinum Contributor 1000 Posts

    The Gap on the Platinum Plugs is....0.60

  8. j cat

    j cat Active Member 1000 Posts

    the gap was changed and so was the plug from OEM factory install.

    the ac delco irridium plugs should be used. this engine like my 2000 is plug picky. the use of this plug has shown me a good improvement when the engine is cold.

    also irridium is a material that takes the high combustion chamber temps with no problem . plat plugs do get damaged from the heat in these engines. I had the plat tips fall off and so did others. these plugs will last for 100,000 miles.

    if you see the gap is not .040 then you do not adjust them. the plug is defective , get another plug. I would check at store all plugs have the correct gap by looking.. using a tool these can be damaged very easy.
    Last edited: Dec 11, 2013
  9. Jeff Dodson

    Jeff Dodson Member

    It's the iridium plugs I have. The direct replacement and they are factory gapped at .040
  10. 99'HEARTBEAT

    99'HEARTBEAT Moderator Staff Member Platinum Contributor 1000 Posts

    As our trucks are both 99"s.....they came from the Factory with Platinum Plugs, that were Gaped at.....0.60.....and GM is now Installing at the Factory, the Iridium Plugs with the Gap at 0.40

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