Another spark plug question.

Discussion in 'Maintenance & Upkeep' started by Pikey, Jan 29, 2014.

  1. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    My 2005 manual calls for a 41-985 iridium, from what I understand it has been replaced by 49-110 iridium. Now here is the issue, checking a few parts sites and ac delco's site they are calling for the AC Delco Rapidfire 6 plug. which just states that it has a longer life than a conventional plug, no materials stated. Anyone have any experience with these? Now searching around more I found that the 49-110 iridium was replaced by the 41-962 double platinum. Any suggestions guys? @99'HEARTBEAT ? I have heard that the 5.3L 2000-2006 does not like the 49-110. I even found a post on another forum from a member, @j cat from 2004 stating that they did not like them. Suggestions?

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    just found this

    View attachment 57491

    apparently a lot of folks saw mpg decreases with the 49-110 iridium plugs in the pre 2007 trucks. I found many people complaining about it during my research
    Last edited: Jan 30, 2014
  2. j cat

    j cat Epic Member 5+ Years 1000 Posts

    ac delco 49-110 I am not familiar with that part/plug #.

    confusion with the proper plug to use was created by GM with the vehicles produced around 2003 period and earlier. GM changed the plug gap from .060 to .040. my OEM .060 plugs failed because the platinum tips fell off. I then installed the .040 plus 2 bosch plat plugs these worked good for 40,000 miles , on inspection I found that the tip was being damaged from the heat. I then put in the 41-985 iridium plugs .040. these so far have worked good. so far with 30,000miles on them the tips are not affected by the heat as the plats were. I just did the MPG check 1700 mi trip and I got 18.3 mpg @70MPH.. 4WD 5.3L ext cab.

    I always got this MPG and the only time I got less was when the vehicle had less than 5,000miles on it. I would use the iridium's with these engines.

    so looking this up I find that the 41-985 IR are no longer made the replacement is the 41-110 IR.. cost more !
    Last edited: Jan 30, 2014
  3. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    Apparently, I confused numbers during my search the number is 41-110. I found a set of 41-985 on amazon and am having them shipped to me. Parts stores around me don't carry them anymore. I don't know if it was you or someone that happened to use the same screen name on another forum, but I found this from 2010.

    j cAT 06-20-2010, 09:41 AM

    update : these new replacement plugs 41 110 are creating issues with our engines as reported on other forums....

    If I need plugs today I would go with the 41 985 delco or another plug manufacturer that users have had good results..since I haven't used this plug I can't say for sure its good , but GM says it is ..

    reports state missfires / poor engine performance ..
  4. j cat

    j cat Epic Member 5+ Years 1000 Posts

    I also got confused with all this plug drama. the 41-985 plugs are running well beyond 100,000 miles . some have reported 185,000mi and still look good. could be why ac delco stopped making them . they last the life of the vehicle...

    I think it was 2005 I installed these plugs. the plugs 110/985 are according to ac delco the same plug. could be they just changed the manufacturing process in some small way. some may have found problems with plug replacing due to improper toque or damage to the plug wires which are hard to remove and some times a little trick to push on to the plug.
    Last edited: Jan 30, 2014

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    Mike.....the 41-985 and the 41-110 Are/Were the Same Iridium Tip Plug, the 41-985 A/C Delco Plug has been superseded by Delco P/N 41-110.......and this change in part number was after the Below GM TSB was Published.

    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 Gapping - (Feb 12, 2007)

    Subject: Information on New Spark Plugs and Gapping

    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)

    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.
    This bulletin is being revised to bring attention to the Set Gap Per Vehicle Specification on the ACDelco® Iridium Spark Plug Boxes. Please discard Corporate Bulletin Number 03-06-04-060 (Section 06 -- Engine/Propulsion System).

    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 1.01mm (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 Gaped Should NOT be Used.
  6. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    thanks Mike. :great: I ended up finding a set of 41-985 on amazon. I could have gotten the 110 at half the price. Oh, well. I know for next time. I am sure that when that time comes There will be some other change
  7. j cat

    j cat Epic Member 5+ Years 1000 Posts

    I doubt there will ever be a need to replace those plugs.
  8. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    that could be true. I bought the truck with 130,000 on it. I pulled a plug then and they "looked" ok, they are the 110's. It had new wires on it so I assumed that the GM dealer that had it changed the plugs also. From looking around the web I found multiple instances where guys were complaining about mpg loss after 20,000-30,000 miles with the 110's (about 3mpg). they installed the 985's and their mpg was restored. I am seeing a steady decrease in mpg (3 mpg, yea, I know winter fuel mixture, and I am grasping at straws here). So, I figured that it is not going to hurt anything except my wallet to throw a new set of plugs in it. Then I know when it was actually last done rather than assuming the dealer did it.
  9. duke0477

    duke0477 New Member

    The Confusion Continues, gapping the ungappable plug?

    Hopefully someone can shed light on this as their is still confusion. I just got off the phone with dealership for my 2007 1500HD Classic 6.0L and they told me I needed the platinum plug, ACDELCO 41-962. They come pre-gapped at .040 and are supposed to be .060 as they are not the iridiums. I even confirmed with the service department that the correct gap is .060. SO I guess I will be adjusting the gap on a plug you are not supposed to be adjusting. Neat!

    There is also the tech bulletin from ACDELCO, WD Bulletin 13D-070, that states:ACDelco announces that 2006-and-older, as well as some 2007, spark plug service applications
    covered by the iridium spark plug 41-110 have moved to the platinum plug 41-962. 2007-and-newer
    applications used iridium plugs in production and service requirements will remain assigned to the iridium plug, 41-110.

    So it is pretty clear that the 41-962 is the right plug for my truck, but the gap is my concern. Any thoughts?
  10. yoymon

    yoymon New Member

    I had the same concerns I ordered ngk iridium plugs for my 2003 called for 60 from factory and they come at 40, I read through some forums and they said leave the gap at 40 so I did, so far so good, only been a few weeks though, no change in gas mileage I just changed them because the plugs and wires were original and I thought maybe age would be a good reason to change

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    by the way before I read up on it a bit I tried to gap one of my iridiums..and broke the tip right off, another reason they say not to gap them I guess, if you don't want to guess or worry just pull a plug out of truck and order or find the same exact ones and order them (assuming they are original plugs)

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