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NGK V-Power Spark Plugs - Heat Range 6 (03-04 Cobra; 07-14 GT500)

Item 525094
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    Features, Videos & Details

    • Perfect for Stock Boost
    • V-Groove Technology
    • Improves Fuel Economy and Lower Emissions
    • Heat Range: 6
    • NGK Part# TR6; NGK Stock# 4177
    • 14mm Thread Pattern
    • Spark Plug Reach 0.690"
    • Sold as a Set of 8
    • Fits 2003-2004 SVT Cobra and 2007-2014 Shelby GT500

    Review & Installation Video

    Justin: Hey, I'm Justin with and this is the Stage 2 Power Pack Bolt-On Build-Up for all 2007-2009 GT500s. This Power Pack is for the GT500 owners who have already taken care of some of the basic bolt-ons; your cold air intakes, your tunes, and are looking for more power out of your supercharged 5.4 liter. Now if you guys are looking for more power out of your Mustang, whether it's a GT500, a GT, or a V6, be sure to check out some of our other Bolt-On Build-Ups by subscribing to our YouTube channel if you haven't done so already.This entire pack is centered around a very popular supercharger mod that's going to increase our boost and therefore increase the horsepower on our GT500. However, just like anything else in the forced induction world, you can't just add more boost without addressing other key areas of your ride to ensure you're getting the most out of each mod, but more importantly to ensure the safety of your motor. So first, let's get to everybody's favorite topic, more boost. The first mod in our Power Pack consists of the Metco Motorsports 2.6 Inch Upper Pulley. Now a smaller pulley like the Metco here is always a very popular choice with supercharged applications because what it's going to allow you to do is spin that stock blower much faster, resulting in more boost. In fact, we should be looking at three to four pounds of additional boost compared to the stock three inch pulley. The Metco itself is a very nice piece and is actually very popular with other GT500 owners here on the site. In fact, if you want, you can just click on the link below to read up on some of the reviews. Now the design is a two piece design, so you have a hub that presses onto the blower shaft first, and then the actual pulley bolts to the hub using the included hardware. This is just basically going to make any future pulley swaps a complete piece of cake. I really can't wait to see what a few extra pounds of boost are going to do to our power number, and best of all, that factory Eaton blower should really be screaming.With the pulley out of the way, let's talk about some of those other supplementary mods that I told you guys about at the beginning of the Pack. Now again, you can't just bolt up a pulley and go without addressing some other areas. Case in point, that smaller pulley has now created some excess slack in our belt which basically our factory idler will not be able to keep up with. What this is going to result in is dreaded boost and power robbing belt slippage. Enter the Metco Double-Bearing Auxiliary Idler Pulley Kit which we also installed on our '08 here. Now this is going to take up the extra slack created by the smaller 2.6 inch pulley and just create plenty of belt wrap to prevent any belt slippage, and more importantly it's going to ensure that those boost levels stay rock solid all the way through the upper RPM range. On top of that, the double bearing construction will ensure a little bit more durability over time, it might actually be a little quieter, and for a few bucks more it's really a no brainer. Finally there's one more part to go over before we bring in Mike J from Bama to tweak the tune a little bit for us, and of course turn the rollers one more time. With that pulley in place, we're really going to be spinning our blower a lot faster than we were before which of course will lead to more boost meaning we had to address our spark plugs. So we installed the NGK TR6 Plugs which really are the go-to spark plug for any Shelby owner who is upping their boost. They're a one heat range colder plug compared to our stock plugs which will help avoid any possible detonation. An important note, just make sure they're gapped correctly before install to avoid any spark blowout. Definitely recommend doing these plugs or something similar whenever you really start cranking up the boost like we are here with the '08.Alright, well with all the new parts in place, we have Mike J from the Bama Performance Team in here working on the new tune for us for all increased boost that we're going to be seeing thanks to that smaller pulley. Now Mike, obviously the car's going to be seeing a lot more boost than we were before. How does that affect things on your end?Mike J: Well basically with the higher boost levels, we're going to be seeing right around 12 to 13 pounds. I've already gone ahead and made adjustments to the ignition timing tables to make sure that we're not going to see any detonation at all. I'm then basically just looking at air-fuel ratio to make sure we're in that sweet spot.Justin: Awesome man, I know those colder plugs should definitely help with that detonation too. Mike J: Absolutely.Justin: Very cool, man. Well if you're all finished up, I want you to hop on out of there because I think it's my turn. I get to hop in, do another pull, and see what the numbers are.[engine noise]At the end of the Stage 1 Power Pack featuring our 2008 GT500, the car was making 508 horsepower and 479 pound feet of torque at the rear wheels. With all the Stage 2 modifications in the Power Pack installed, we were now putting down 548 horsepower and 545 pound feet of torque making for a gain of 40 horsepower over our Stage 1 numbers, and gains of 66 horsepower and 71 pound feet of torque throughout the curve. The Stage 2 Power Pack with pulley and supporting mods is always a favorite of GT500 owners, and I think it's pretty easy to see why. Honestly, there's nothing that compares to swapping those upper pulleys and really cranking up the boost.Hey, that's going to do it for the Stage 2 Power Pack Bolt-On Build-Up for all '07-'09 GT500's. Be sure to check out the other Power Packs for the GT500s and don't forget to subscribe to our YouTube channel if you haven't already. Thanks again for watching, and for everything Mustang, keep it right here at

    Regular Maintenance. Replacing your old weak spark plugs is paramount to keep your engine running smoothly and efficiently, so why replace them with the same old sub-par stock plugs when performance V-Power plugs from NGK will improve fuel efficiency and lower your emissions.

    Superior Design. NGK V-Power Performance Spark Plugs feature a copper core for its superior conductivity and a durable nickel alloy tip to assure a strong spark to keep your stang running at it's peak efficiency. The V-Power plug features a unique V-Groove that allows the spark to happen at the edge of the center electrode, so that the heat is not absorbed by the electrode itself, resulting in a complete efficient burn.

    Application. This set of eight (8) NGK V-Power Performance Spark Plugs are specifically designed as a direct fit replacement for the 2003-2004 SVT Cobra and the 2007-2014 Shelby GT500 Mustangs.

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

    MPN# TR6

    CA Residents: WARNING: Cancer and Reproductive Harm -

    What's in the Box
    • (8) Spark Plugs
    Installation Info
    Tech Specs
    Will it fit my Mustang?

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        Questions & Answers (11)

        5 Top Rated Questions

        Hi, what gap for 2.6 pulley, idler pulley and twin65mm cobra jet throttle body? also, Air raid cold air intake. Thank You! This is all on my 2009 gt500.

        • These would come pre-gapped, however, you may need to increase or decrease for your exact application.

        Helpful (4)

        Hi anyone what’s the gap on the spark plugs with a 2.6 pulley being install thanks

        • These would come pre-gapped, however, you may need to increase or decrease for your exact application.

        Helpful (1)

        Will these plugs work for a 2004 Mach 1 on 100 shot of nitrous? Are they cold enough, my car just has the basic CAI and exhaust. I want a good nitrous plug.

        • The NGK V-Power Spark Plugs - Heat Range 6 (03-04 Cobra; 07-14 GT500) are really designed to be just an upgraded factory replacement plug. I would not recommend these plugs for a nitrous setup. I would recommend a lower heat range spark plug.

        Helpful (1)

        I have a 2000 GT on 12psi? Will these work or do you have a suggestion?

        • These NGK V-Power Spark Plugs will work great with your 2000 GT.

        Helpful (0)

        What should the gap be set to on an '09 GT500 with these plugs? Stock coils, upper pulley, ~550hp. I assume how they come pre-gapped is incorrect?

        • With the NGK V-Power Spark Plugs, we recommend a starting gap of 0.032" though some minor adjustment from here may be required, depending on your vehicle.

        Helpful (0)
        Post Your Question
        6 More Questions
        What’s the correct gap for a 2013 GT500? I checked all mine and they are .038. I’m running over 700HP. 1 answer
        I know it’s not listed, but will these fit a 2013 Mustang gt 5.0? 1 answer
        Are these plugs pre-gapped. The video on your stage 2 upgrade for 2012 GT500 says to make sure they are gapped correctly? 1 answer
        On the 2010 gt500 bolt on build up. It suggests installing one heat range cooler spark plug. It references this plug. On the NGK website it lists this heat range as stock plug for this application. You don't offer this plug in a cooler heat range. Am I missing something here? Thanks!, Tom 1 answer
        These spark plugs are listed in the 99 Mustang GT section. However, I do not see that they are meant to work with my year of Mustang. Are these still compatible with my 99 mustang? 1 answer
        What is the gap for these plugs? I checked several of them and they are at about .34 from NGK. 1 answer

          Customer Reviews (37) Write a Review

          Ratings Summary

          4.7 out of 5 overall rating from 37 customers

          Installation Time: Less than 1 Hour

          Installation Cost: 0-$100

          • August 10, 2019

            5 2010 GT500 - 2010Gt500 Installation Time: Shop Install Installation Cost: 0-$100


            My 2010 Gt500 is running like brand new, couldn't be happier.

            Helpful (0)
          • October 19, 2018

            2 2010 GT500 - PaulW Installation Time: Less than 1 Hour

            They do not last in a SC vehicle

            I figured they were good plugs and would last a long time..wrong...had engine misses after 6-7thousand ....changed tunes, plugs, TB,,,,,turned out the plugs were the issue. Then I read that they will not last in a SC engine and I should be using platinum or better plugs...only $2.xx per plug ....made the change and now it is running great again. These plugs looked fine when I pulled them and looked them over....all were same color and looked normal without wear...It was not a connection problem or coil issues either...definitely a plug issue.

            Helpful (5)
          • July 16, 2018

            5 2008 GT500 - Mrbalisongguy Installation Time: Less than 1 Hour

            Fixed my issue

            These are one of the few options i have with my shelby but they work great and fixed a misfire that was causing my car to run terribly. found out i had a bad water issue with one of the plugs and caused me to need to get a new set early. i’m glad they’re priced so well!

            Helpful (6)
          • July 09, 2018

            5 2013 GT500 - 662Horsepower Installation Time: Less than 1 Hour

            2013 Shelby GT500

            Easy to install. I was a little worried about wrenching on my Shelby. I have worked on all my old cars but this was more than I had done to this car. Along with the 2.4" pulley, the extra pulley, and the Bama tune it seems to make a little more power. More power means more fun.

            Helpful (7)
          • May 10, 2018

            5 2004 Cobra - LauroCobra Installation Time: Afternoon

            Worked Great for my 04 cobra!

            Came in on time and was very easy to install plug and play pretty much!

            Helpful (5)
          • May 03, 2018

            5 2003 Cobra - Andrew3 Installation Time: Less than 1 Hour

            NGK is great!

            Great product/quality for the money! Definitely a great upgrade over stock plugs!

            Helpful (6)
          • March 07, 2018

            5 2011 GT500 - MasonS Installation Time: Less than 1 Hour

            Highly recommended

            Stock plugs were throwing some false knock. Tuner recommended the plugs and the knock went away and car is driving a lot better. Best 30 dollar investment you could make

            Helpful (8)
          • January 11, 2018

            5 2003 Cobra - BlaineJ

            Boost Fixer

            My 2003 cobra was blowing out spark over 9 psi of boost. put these plugs in at .035 and it solved all boost issues.

            Helpful (8)
          • December 21, 2017

            4 2004 Cobra - DennisW Installation Time: Less than 1 Hour

            Spark plug

            Best bang for the money. It works great. I used a few set to retune my cobra.

            Helpful (8)
          • December 11, 2017

            5 2012 GT500 - JamesC Installation Time: Less than 1 Hour

            NGK V-Power Spark Plugs

            Great Price easy to install One of the best plugs for your Shelby

            Helpful (7)
          • November 26, 2017

            5 2004 Cobra - mayosvt Installation Time: Afternoon

            Runability is 10x better.

            With the tr6 plugs, there will always be a slight miss at idle. It did change the way the car ran after recapping and installing an accufab tb and inlet though. Great purchase, quick shipping.

            Helpful (7)
          • October 17, 2017

            3 2010 GT500 - PaulW

            Half rating for half the supply!

            Seeing how I have only received four of the original 8 and still waiting for a month....even 3 is probably too high.

            Helpful (8)
          • October 16, 2017

            5 2003 Cobra - PaulC Installation Time: Less than 1 Hour

            Great product

            Great plugs for my stock cobra! Will be using also for boltons!

            Helpful (7)
          • July 05, 2017

            4 2003 Cobra - 97CobraSVT Installation Time: Less than 1 Hour

            Good plugs !

            Really the only spark plug I run with my cobra's , so I highly recommend these !

            Helpful (10)
          • July 02, 2017

            5 2003 Cobra - HoustonTull Installation Time: Less than 1 Hour

            Great product for a good price

            My cobra was starting to miss hard during acralation. Bought these plugs that plugs because they were recommined on the forums and couldn't be happier. Fixed my issues and where much cheaper than other plugs out there.

            Helpful (7)
          • April 26, 2017

            5 2011 GT500 - EricJ Installation Time: Afternoon

            What a difference!

            I upgraded the pulley and went to a 2.5 so I went with a colder plug and let me tell you these plugs were super easy to install and these along with the other mods made a HUGE difference in performance. If you change your pulley and go smaller these plugs are the way to go!

            Helpful (10)
          • April 19, 2017

            5 2007 GT500 - MSJR Installation Time: Less than 1 Hour

            Great product!

            These plugs work fantastic on my 2007 Shelby GT500, I am very pleased!

            Helpful (8)
          • April 14, 2017

            5 2003 Cobra - Mike Installation Time: Less than 1 Hour

            Big difference

            This is my second set of ngk tr6 plugs! I love them.

            Helpful (7)
          • March 31, 2017

            4 2008 GT500 - Night500 Installation Time: Less than 1 Hour

            GT 500 Plugs

            Several things had to be moved, to be able to install the plugs. Plugs looked to be of good quality.

            Helpful (7)
          • March 15, 2017

            4 2012 GT500 - RomJ Installation Time: Less than 1 Hour

            Good plugs

            I have always used tr6 plugs in all my mustangs. Great plugs for a range of power levels. Smooth starts and great responsiveness. Paired with good coils or ignition system you have a good bang for your buck.

            Helpful (7)

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