I am replacing the spark plugs on my engine, and the manual calls for Denso IK24C11 plugs. However, it does not appear that Denso makes these any longer. I cannot find them on their website (although IK24 plugs are available). I have been given various conflicting answers about plugs that cross-reference (including Denso 5311 and 4709). How do I go about (1) finding the specs from the old plug and (2) cross-referencing those to a new plug.

  • Have you checked this sparkplug cross reference website? Commented Feb 13, 2019 at 19:20
  • @Pᴀᴜʟsᴛᴇʀ2 yes and it gives me a third answer Commented Feb 13, 2019 at 19:31
  • The issue of answering your question is, it's doubtful Denso's specs will align with ACDelco's spec, or NGK's specs, or ... insert your manufacturer here. The thread and depth are the easy parts. The heat ranges won't be. Realistically your best bet is to go to a parts store, or RockAuto.com, or (heaven forbid) the dealership and ask them what the replacement part number is by looking up your vehicle ... that is, if you don't trust what I've shown you in the link. Commented Feb 13, 2019 at 19:34
  • @Pᴀᴜʟsᴛᴇʀ2 My concern is that this goes in an aircraft engine (HKS-700T) that is no longer in production. No auto shop has anything in their database about that engine and I don't want to risk choosing the wrong plug. Commented Feb 13, 2019 at 20:02
  • 1
    Still sold in the UK...sparkplugs.co.uk/denso-iridium-spark-plug-ik24c11
    – Moab
    Commented Feb 15, 2019 at 16:36

1 Answer 1


I found the new plug recommmended by the engine manufacturer. The correct plug is the HKS Super Fire Racing Part Number 50003-M40i

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