Always ensure the vehicle you are working under is supported securely with jack stands, wear appropriate clothing and safety goggles.  Be weary of your clothing and the proximity to moving parts.  If you are uncomfortable about attempting an installation, DON'T......Seek a qualified service person or facility to help with your installation.  This articles contained in this site are in addition to and enhancement of existing OEM specified procedures and practices.  With regard to specifications and procedures, the OEM manual, procedure or practice shall dictate and govern.

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When you are working under your vehicle, make sure it is supported by secure jack stands.  There is always accident reports indicating someone has perished because of working under a car that was only supported by the jack.  Do not take any chances.....

One of the best HP/$ upgrades that you can make to your Mustang is the addition of underdrive pulleys.  The installation frees up between a 8 and 10 hp to the rear wheels by reduction friction drag on accessories driving by the crankshaft of the motor.  

Here is the mechanical explanation of how this works.  The alternator and the water pump are 2 accessories that are driving by the serpentine belt.  Both of these units operate at a higher rpm than they really need to, basically over producing as a safety factor.  The installation of underdrive pulleys replaces the stock harmonic balancer and pulley with a smaller one, and replaces the water pump and alternator with a larger one.  The final result is the reduction in component rpm by about 25% therefore releasing HP directly to the driveshaft.  It just doesn't have to work so hard to turn these 2 components.

This is similar to riding your 10 speed bicycle.  When you switch to a lower gear, your pedals go faster but your speed slows down.  It takes less work for you to pedal because you have a better mechanical advantage over the lower gear you have chosen.

The installation is not that difficult but there are some snags that you will have to deal with.  The removal of the alternator pulley is difficult without an impact wrench.  First things first, loosen the bolts on the water pump pulley while the serpentine belt is still in place.  Do not remove it yet, you have to remove the belt first.  Once the belt has been removed, direct you attention to the alternator.  I removed this one completely, stopped by the local Checker store and had them spin off the pulley and zap the new one on for me.  Took all of 20 seconds.  They don't advertise that they do this because of liability reasons, so check with them first to see if they are willing to do it for you.

Replace the alternator and make sure that all the electrical connections are back in place.  Next, install the new water pump pulley and tighten the bolts as much as possible.  I used a rubber oil filter wrench to resist the pulley during tightening.

The next step is to work on the harmonic balancer or crank shaft pulley.  We chose the Steeda Pulleys as they replace the harmonic balancer completely.  There are some products on the market referred to as piggy back and they do not work a well.  These are installed over the existing stock harmonic balancer and do not reduce the "rolling" weight of the pulley.

You will need to jack the car up as far as possible to get the proper access to the lower pulley.  Set the parking brake on as hard a possible and if you have an automatic, you will need to restrain the transmission with a special tool.

The bolt that holds the pulley on has had some lock tight applied at the factory.  With the parking brake set as hard a possible, you will notice that you are going to be taking up a lot of the slack in the drive train by trying to remove this bolt.  You will need the extra space under the vehicle to turn the bolt far enough to break it loose.  You may need to add a snipe (pipe extension) to your strong arm to give you extra leverage on the bolt.  Once you are able to break the bolt loose you will need to use a gear puller to remove the pulley.  You can rent these from Checker as well. 

The harmonic balancer is fairly heavy so be careful not to drop it when you get it free of the puller.  When installing the new pulley, you must put a dab of silicone sealant on the keyway of the new pulley.  This prevents oil from working it's way up the keyway and getting by the seals.  To install the new pulley, you will need to use the bolt supplied.  The stock bolt is not long enough to start the pulley on, you will only use the longer one to get the pulley started, then re-use the stock bolt and washer.  Do not forget the washer.

When you follow the supplied instructions for torque specification, it will seem a little odd.  They will probably indicate to torque first to a high number and then back off and re-torque to a lower number.  The initial torque spec is to seat the new pulley on the tapered shaft of the crank.  The second torque spec is for the bolt itself.  Do not leave the bolt torqued to the first specification or you will have a very difficult time trying to remove it later on.

With the new pulley on, the water pump pulley bolts tightened and the alternator replaced, it is time to put the serpentine belt back on.  The Steeda pulleys do not require a different belt.  Once you have the belt installed, start the car and let it idle, making sure that the belt is tracking properly on all the pulleys.  Stop the engine and check that there are no nicks on the side of the belt and that it is still tracking properly now take her for a spin and enjoy, this is a real "Seat of the Pants" improvement.