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NGK Iridium IX Performance Spark Plugs - Heat Range 8 (03-04 Cobra; 07-14 GT500)

Market Price $99.99 You Save 10% ($10.00)
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$89.99 (set of 8)

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  • Item 64072
  • MPN#3691

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    Features & Details

    • Perfect for Increased Boost
    • Iridium Tip for a Constant Stable Spark
    • Improves Fuel Economy and Lower Emissions
    • Heat Range: 8
    • NGK Part# TR8IX; NGK Stock# 3691
    • 14mm Thread Pattern
    • Spark Plug Reach 0.708"
    • Fits 2003-2004 SVT Cobra and 2007-2014 Shelby GT500
    • Sold as a Set of 8
    High Performance. Keeping your Mustangs high performance engine running smoothly and efficiently is important, so routinely replace your old weak plugs with a new set of NGK Iridium IX Performance Spark Plugs for constant reliable spark power. The Iridium IX plugs from NGK will provide improved throttle response, fuel efficiency, lower emissions, and will reduce fouling.

    Superior Materials. NGK Iridium IX Performance Spark Plugs feature a copper core electrode for its superior conductivity and an iridium tip (which is 6X harder than platinum) for it's extremely high melting point, perfect for keeping your Mustangs high-performance engine running at it's peak. And as an added bonus the Iridium IX plug features Trivalent Metal Plating for it's superior anti-corrosion and anti-seizing properties.

    Application. This set of eight (8) Two Heat Range Cooler NGK Iridium IX Performance Spark Plugs are specifically designed for the 2003-2004 SVT Cobra and 2007-2014 Shelby GT500 Mustangs that are running more boost.

    Fitment: 2003 2004 2007 2008 2009 2010 2011 2012 2013 2014 Details

    What's in the Box
    • (8) Spark Plugs
      Hardware included:
    • None Required
    Installation Info
    Tech Specs
    Will it fit my Mustang?

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    4 Questions / 5 Answers

    Ask a Question

    Ford racing 750 HP Kit I have 2012 Shelby GT 500 in the process of installing a ford racing 750 HP Supercharger Kit with long tube headers catted X Pipes and manga flow cat back system! Which spark plugs and coil on plug kits can I use to complement this setup Thanks

    RajunCajun

    • These NGK Iridium IX spark plugs are a colder than stock heat range on your 2012 GT500 and are recommended for an increased boost application.

      AMSam

    Show 1 more answer Helpful (2)

    I recently installed a 2.8 pulley and belt tensioner on my ‘04 Cobra, I have my Bama tune but not sure on what I need to do about my plugs. Do I need new ones or regap the stock plugs? If I need new ones what heat range do I need?

    AnthonyC

    • Spark plug selection will depend on your other modifications and horsepower output. As a general rule of thumb, you will decrease the spark plug heat range for every 100hp added to a supercharged, turbocharged, or nitrous vehicle.

      AMRobD

    Helpful (0)

    What is the gap for a 2014 GT500 with a 2.4 Metco Pulley, a Ford Racing Cobra Throttle Body, and a JLT Big Air Intake with BAMA tunes?

    Ray80

    • We would recommend the stock gap for your GT500 for most applications, however, with the modifications on your vehicle, we would recommend using the gap which was specified when Bama programmed your tune.

      AMJEFF

    Helpful (0)

    Do these spark plugs plug and play or needs to be gap for gt500?

    sergioGT500

    • The spark plugs do come pre-gapped; however, with any spark plug - these included - it is highly recommended that each plug be checked prior to installation to ensure that everything is as it should be!

      LisaS

    Helpful (0)

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    Customer Reviews (6) Write a Review

    Overall Rating 4.8

    out of 5 stars

    Installation Time:Less than 1 Hour

    • Performance Gain 4.5 4.5
    • Fit 5 5



    • 5/5

      Installation Time: Less than 1 Hour

      June 06, 2018

      Plug and coil pack installation

      Noticable performance increase combined with Ford Performance coil packs.

      MichaelT

      Year: 2003 Submodel: Cobra

      Helpful (1)

    • 5/5

      Installation Time: Less than 1 Hour

      May 28, 2018

      Great product!!!!

      Money well spent The plugs came with the proper gap, unlike others on the market. Where you have to re-gap at least 3or4 out of the eight.

      ShawnK

      Year: 2011 Submodel: GT500

      Helpful (1)

    • 5/5

      Installation Time: Less than 1 Hour

      April 07, 2017

      Modified gt500 2010

      I added these plugs with a pulley/idler and cai tuner kit, as well as afco racing radiator and 170 thermostat. Very pleased with the responsiveness of the engine now and the plugs fit very well for the modifications done. Would recommend these plugs for anyone looking to do minor modifications to their turbo or supercharged mustang applications.

      ElliotD

      Year: 2010 Submodel: GT500

      Helpful (3)

    • 5/5

      Installation Time: Less than 1 Hour

      January 04, 2017

      Amazing quality!!

      These Iridium Plugs really make all the difference! NGK is an awesome brand as always but once you start adding Boost and get a performance tune you'll notice that your car is gonna be running insanely rich and idle pretty rough. In my case I also noticed a small decrease in power as well because of my high altitude. I knew that I needed to get a better plug that would provide a stronger faster spark to be able to keep up with the new performance tune and added Boost. I purchased these NGK Iridium plugs with an 8 heat rating and it has definitely been a night and day difference! I have all my power back and my motor is running stronger and smoother than it ever has before! I've always been a huge fan of NGK plugs and they've never let me down. These new Iridium plugs have actually impressed me more than usual, if it's at all possible I feel that they have stepped up their game once again!!

      Am2drag

      Year: 2007 Submodel: GT500

      Helpful (4)

    • 4/5

      Installation Time: Less than 1 Hour

      April 29, 2016

      Good product. Did not solve my pre ignition

      Good quality product made for smoother city driving. But i thought going down a few temperature ranges would solve my pre ignition problem under heavy load. Must be an intake temperature issue.

      Theblosse

      Year: 2007 Submodel: GT500

      Helpful (4)

    • 5/5

      Installation Time: Afternoon

      February 07, 2016

      Very good but a little pricey

      I bought these a wile ago and they work amazing well. I was having some idling issues and these completely fixed that as well as adding to the responsiveness of my car. My only complaint is that they are a little pricey, other than that I love them. Great job AM!

      Jake

      Year: 2003 Submodel: Cobra Corvallis, OR

      Helpful (4)

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