Another spark plug question.

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

  1. McClintoc

    McClintoc ɹoʇɐɹǝpoɯ Staff Member 4 Years 1000 Posts

    Yikes, I am glad I saw this thread.

    Other than to the plugs themselves, can any damamge result to the engine for improperly gapped plugs?

    I changed my plugs about a year ago and was unaware of any TSBs. This was the second time I changed my plugs. The first time I chagned my plugs was before the TSB mentined above and my gap was still .06. This last time, I gapped them at .06 like I did the first time but it sounds like they should be at .04. Am I ruining my engine or just the plugs?
  2. duke0477

    duke0477 New Member


    Yes, for Iridium plugs the gap is supposed to be .040, but I was told by the dealership for the '07 6.0L Classic that the stock plug was PLATINUM (41-962), which calls for a .060 gap. If you search for the tech buletin I mentioned in my previous post ACDELCO called for 06 and older along with some '07s (like the classic Silverado) to use the platinum plugs. I am not saying Iridium will hurt those vehicles, but ACDELCO is stating to use the 41-962s that are platinum.
  3. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    The plugs should all come pre gaped. you should not adjust them or you can damage the plug. The only thing you might hurt with improperly gaped plugs is some performance loss and mpg loss

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

    x2....on what Pikey"Mike" has mentioned and as the GM TSB expresses, regarding the Gap on the"Iridium Spark Plugs" on the first page of this Thread, 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.

    Here's the A/C DELCO BULLETIN, Regarding the A/C Delco Platinum and A/C Delco Iridium Spark Plugs,

    Date: May 21, 2013 Bulletin Number: 13D-070
    To: DDG Headquarters and Branches Category: Product
    From: Brad Brunken, Product Development Line(s): 41

    Subject: A/C Delco Spark Plugs 41-110 and 41-962 - Application Update.

    Description: A/C Delco 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. For the older Model Years, GM used a Double Platinum Spark Plug in Production, and these Older Applications are to be Serviced with the Double 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. Both Plugs Meet Original Equipment Specifications for the Applications Designated.

    Catalog: Changes for the Epicor and WHI systems will be updated in the June release 2013. A/C Delco Recommends you begin adjusting your Stocking Requirements for the 41-962 in Preparation of the Upcoming Catalog updates. The Estimated Sales Volume Split between the Two Spark Plugs is 50/50 based on these Application changes and Vehicles in your Markets.

    Please refer to Electronic Catalog Provider for Complete Application Information. These Plugs fall into the family pricing matrix for double Platinum and Iridium Plugs. The 41- 962 will be Less Expensive for Older Applications and will Keep A/C Delco Competitive in the IAM.

    General Information: Here is the Reference Bulletin Attachment for Year, Make and Model Applications for Each of These A/C Delco Spark Plugs.

    Link,[PDF] August I 2013 - ACDelco TechConnect
  5. Hawch

    Hawch New Member

    I am new to the forum and recently bought a 2004 GMC Sierra 5.3L. I have been looking everywhere for a straight forward clear cut answer to which AC Delco spark plug I should put in my truck and cannot seem to find it. Can someone help me by telling me whether I should buy the original 41-985, the changed part number 41-110, or the 41-962?
  6. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    I put the original 41-985 in mine. I had found some reports on the web of guys loosing mpg going to the 41-110 even though GM says they are the same
  7. j cat

    j cat Epic Member 5+ Years 1000 Posts

    well having used OEM factory plats then bosch plus 2 , now iridium 41-110 these plugs are the best. reason is they work under the high heat in these combustion chambers the plats can not handle this heat.. these 110 plugs will last well over 100K miles and still look new. some have gone 200K but I would not do it because you will have replacing problems.

    when replacing plugs make sure you measure the resistance of the plug wires .. should be around 450 ohms.... always put dielectric grease in the boot ends both ends.. this will ensure no wire damage from water.
    thegawd likes this.
  8. Hawch

    Hawch New Member

    Thats what I found as well so was leaning toward going to the 41-985 and you confirmed that for me. Now the problem is that I can't find them anywhere! Any ideas? Looked online and called local shops, all carry the 110's instead. Starting to wonder if the change in performance or mpg loss is perhaps a placebo effect of the number being different so results must be different or something else all together. Can someone confirm with certainty that the 110's in fact didn't perform well? As in put in the 110's saw bad mpg's, switched them back to 985's with no other changes and saw quick improvement? The 41-962 thing confuses me even further so if possible can we leave that out unless someone has a really strong argument from experience for or against their use. Thanks, just want to get this figure this out.
  9. Hawch

    Hawch New Member

    J cat I wrote my last post before seeing yours, thanks, good info.
  10. j cat

    j cat Epic Member 5+ Years 1000 Posts

    last winter I did a FLA. to MA. trip 1700mi each way got 18MPG plus down and back 87 OCTANE . 70-75 MPH with a good amount of personal stuff for a months stay. the 110 plugs have 20k miles on them. this is the MPG I have been getting since new ..summer time driving close to 19 MPG. 18 MPG plus was great and that was with the 14 year old O2 sensors.. put new O2 sensors in so , MY guess is the MPG should be a little higher closer to the 19 MPG.. also the engine idles very smooth 155K miles.. good luck with the plugs...

    forgot to say to not mess with the GAP... if it looks off the plug is defective !!!! these are with a warranty..

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