Free Shipping On Orders Over $49. Details

Talk to a Mustang Enthusiast
M-F 8:30A-11P, Sat-Sun 8:30A-9P
Win $15,000!! Enter Now
Coronavirus: We are Open For Business, Prioritizing health and safety Learn More

Auxiliary Idler Pulley Kit; Double Bearing (07-14 GT500)

Item 49704
Call a Mustang Enthusiast at 1-877-887-1105
M-F 8:30A-11P, Sat-Sun 8:30A-9P
Market Price $228.99 You Save 4% ($9.00)
Our Price


FREE Shipping

Will this fit your Vehicle?

Select a different vehicle Help?
Update or Change Vehicle
In Stock

Ship to: Ashburn - 20149
Sorry, please enter a valid US or CA postal code
We're sorry, zip can't be updated at this time.
    Create a list
    Add to New List

    Saved - View your saved items

    We're sorry. We couldn't save this product at this time.

      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

      Product Information

      Features, Description, Reviews, Q&A, Specs & Installation


      • Eliminates Belt Slippage
      • 90mm Double Bearing Idler Pulley
      • CNC-Machined Aluminum
      • Allows Original Supercharger Belt to Be Reused
      • Fits 2007-2014 Shelby GT500 with Smaller Diameter Pulley


      Eliminate Belt Slippage. Is belt slippage robbing your Shelby GT500 of power? Then reclaim it with a Metco Motorsports 90mm Double-Bearing Auxiliary Idler Pulley Kit from AmericanMuscle. The Metco idler pulley bolts up just to the left of the supercharger pulley allowing for maximizing belt wrap and to eliminate slippage.

      Superior Materials. The 90mm double bearing idler pulley and mounting bracket included in this kit are CNC-machined from billet aluminum for superior strength and bolt directly to existing bolt bosses with no modifications required for installation.

      Application. This Metco Supercharger Double-Bearing Idler Pulley Kit is specifically designed for use on the 2007 to 2014 Shelby GT500 Mustangs equipped with the Supercharged V8 engine, that have upgrade to a 2.4", 2.6" or 2.8" Metco Motorsports Supercharger pulley.

      Technical Note. Will not fit with Whipple 4.0L supercharger.

      Fitment: 2007 2008 2009 2010 2011 2012 2013 2014

      MPN# MSI-90D

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (31)

      Write a Review

      Ratings Summary

      4.7 out of 5 overall rating from 31 customers

      Installation Time: Afternoon

      Installation Cost: $100-$250

      • May 02, 2019

        4 2007 GT500 - JeremyE

        Pulley kit

        Definitely helps with the belt slippage, and looks great under the hood. Only issue is a lil noisy while cold until unit warms up. Hoping bearing squeal will go away as unit breaks in.

        Helpful (0)
      • April 06, 2019

        3 2012 GT500 - SteveSnow Installation Time: Less than 1 Hour

        GT 500

        Good product and easy install. Looks great and is very quiet. Still get some belt slip at high rpm's after coming off the dyno.

        Helpful (0)
      • February 04, 2019

        5 2010 GT500 - StevenM Installation Time: Less than 1 Hour

        Auxiliary Idler on 2010 Shelby GT500

        Bought the Aux idler because I could feel the power kinda surging under high boost. I have the 2.5” pulley and 90mm idler installed. The Aux idler was the last thing to try before I went for a compression test. The Aux idler made a HUGE difference. The belt, which was a brand new Ford replacement belt, must have been slipping big time!! All my friends noticed a difference. I’m guessing, if I had to put a HP figure to it, 30-40 HP gain from the belt not slipping. I was putting down 520whp/536ft-lb torque. I haven’t had a chance to get it re-dyno’d at Pro Dyno since the Aux pulley install but I’m looking forward to seeing Dan for a dyno run and maybe a re-tune.

        Helpful (3)
      • December 10, 2018

        5 2010 GT500 - GT5hundo Installation Time: Less than 1 Hour

        A must

        Great product, a must when upgrading to a smaller pulley

        Helpful (3)
      • November 29, 2018

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

        Great pulley, great service from AM

        Easy install. Works like a charm. The pulley is high quality, make sure to have some thread locker on hand prior to avoid a trip to the store.

        Helpful (3)
      • October 21, 2018

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

        Works well

        Good accessory. Works as intended. Install was simple just ensure you use lock-tight so it cant vibrate loose.

        Helpful (3)
      • October 11, 2018

        5 2010 GT500 - MacM Installation Time: Less than 1 Hour

        Metco auxiliary pulley

        Great product easy installation....maybe 30 minutes to an hour depending on skill level ...AM is #1 in my book

        Helpful (3)
      • October 09, 2018

        5 2007 GT500 - Bruce Installation Time: Shop Install

        Dang! what a difference in HP!

        Added a smaller pulley and the Idler pulley to my 2007 Shelby GT500. Never ran so good! Love it!!!

        Helpful (3)
      • August 23, 2018

        1 2013 GT - Scott Installation Time: Less than 1 Hour

        Works as advertised

        This product works great if you have a GT500, but it doesn't match up on the hardware side when it comes to a 2013 ROUSH Charged GT.

        Helpful (5)
      • July 09, 2018

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

        2013 Shelby GT500

        Easy Easy Easy to install, unless you drop a bolt. It took me at least two hours to find that dang thing. Looks good on the front of the motor, makes everything look like it needs a polish.

        Helpful (5)

      Questions & Answers (8 answers)

      5 Top Rated Questions

      comparison with single bearing Is having the double bearing better than the single bearing version?

      • Yes 2 bearings make it more stable and giving you a longer lasting pulley.

      Helpful (2) Show 1 more answer

      will this work with the Steeda 2.65 pulley?

      • Yes this will work with your 2.65 inch pulley on the stock blower

      Helpful (0)

      Can you use this with stock setup on a 13gt500 or is this only for use with aftermarket supercharger pulleys?

      • This is only for use with a smaller than stock pulley.

      Helpful (0)

      Does this product fit a Kenne Bell 2.8 water cooled super charger?

      • The Metco Motorsports Auxiliary Idler Pulley Kit is designed for the factory supercharger on the GT500

      Helpful (0)

      Can you use this with a Whipple supercharger?

      • This Metco Supercharger Double-Bearing Idler Pulley Kit is specifically designed for use on the 2007 to 2014 Shelby GT500 Mustangs equipped with the Supercharged V8 engine, that have upgrade to a 2.4", 2.6" or 2.8" Metco Motorsports Supercharger pulley. It will not fit with a 4.0L Whipple supercharger.

      Helpful (0)
      Post Your Question
      3 More Questions
      I have a 2007 gt500 and I am putting on a trinity tvs with 2.4 inch pulley. Will this work well with my setup? 1 answer
      I have a 2008 roush stage 3 mustang , have installed these parts from you ford hot cams ,headers ,cold air intake, bama tuner. at idle the idler make noise because of the cams will the auxiliary pulley kit take care of this problem ? and can I puy a smaller pulley on it to get more boost ? 1 answer
      Metco idler pulley kit I have a 2.6 pulley installed already with my tune after install of the idler pulley kit do i need to get my car re-tuned? 2 answers

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (1) 90mm Idler Pulley
      • (1) Mounting Bracket Plate
      • (3) Fastner bolts

      Tech Specs

          Related Mustang Categories