Performance Pulley Installation on a 95+ J-body

Purpose Of This Modification

By replacing your stock pulley with a Mantapart OEM style pulley (which is considerably smaller), you can reduce the strain on your engine by getting back horsepower taken from the stock pulley. Your approximate gains in Horsepower would be around 5, but remember, this horsepower was already there, it just was being used to turn the pulley! This job will take between 1-3 hours, depending on your experience and tools. You will also likely need a friend (or more!).


  1. Jack up the car and remove passenger side wheel. Remove the wheel well to expose the pulley. You'll need some screwdrivers to get the wheel well off. There may be some cheap plastic connectors holding part of the wheel well, but they are cheap at any auto parts store, so you might as well replace them if they break. You'll also need to undo some wire harnesses for the anti-lock brakes. Be sure to put the emergency brake on, and block the wheels so your car doesn't move.
  2. Remove the bolt which holds the pulley onto your engine. It is probably a size 1 1/16 inch bolt. It's very tight, so you might need something to get some leverage on it. Also, there is a tool that you can use to keep the pulley from rotating while you're doing this, but I just jammed a wrench into it to keep it form moving. This was pretty tricky.
  3. Cut off your old belt, or remove it by torquing the tensioner. The tensioner sits underneath the alternator, and is a small wheel with a spring that keeps the belt tight. There is a 13mm bolt in the middle of the tensioner that you should torque to reduce the tension on the belt. You'll need a pretty long wrench to get to it, and it has to be skinny so that it can fit down there.
  4. Remove the pulley with a pulley puller, a.k.a. harmonic balancer puller. This cost me $20US at Pep Boys. Find the cheapest one that you can get. You could probably return it when you're done, if you're that cheap. (Anyone want to buy a pulley puller- slightly used!) I have no idea how you could get it off without the pulley puller, so you might as well buy or borrow one.
  5. Line up the new pulley so that it fits over the shaft. Try to push it on as far as you can, but you might need a mallet or hammer to bang it the last little bit. Tighten the bolt back on to about 100 or 120 ft-lbs (real tight). Again, there is a tool to keep the pulley from rotating, but I just jammed a wrench into it to keep it from moving.
  6. Put the belt back on. This is one of the toughest steps. Here's how I did it: First, get a friend to help. Wrap the belt around all of the pullies except for the alternator (the smallest pulley on the top). Have your friend keep the belt from falling by holding the belt by the alternator pulley. Next, I put the car in 5th gear, put one of the lug nuts on the hub, and turned the front wheel with the lug wrench so that the engine would turn the belt. I know it's crude but it helped. While you're turning the front wheel (and engine), torque the tensioner with your handy 13mm wrench. It will rotate about 20-30 degrees towards the front of the car, if you're doing it from underneath the wheel well. Have your friend guide the belt onto the alternator while you're turning the engine and torquing the tensioner. If you can think of a better way to do it, go for it! By the way, you can't do it this if you have an aftermarket limited slip differential, because you can't rotate one wheel to make the engine turn.
  7. Start the car to make sure the belt doesn't come off. If all looks good, turn your car off and clean up. Good luck!


Instructions for this modification by Chris. If you have any questions or comments, you can direct them to or directly to Chris.