This is probably a silly idea, but curious to know if anyone has done it. Has anyone removed their factory pulley, had a machinest turn it down to equivalent of 15% smaller diameter, then put it back on the SC shaft?

 

I think the stock pulley is pressed on so it's probably not going to go back on as snug. The aftermarket pulleys get bolted to a hub that clamps down on the shaft as the bolts are tightened. Otherwise, I'm sure you could spin it up between centers (probably using a drive dog) and turn it down. The hardest part of that would be to keep the ribs in the same locations.

 

I don't know if it's possible, but I do know for set-up time and shop rate, you might as well buy one allredy done. It is not as easy as just chucking it up in a lathe and turning it down. The grooves are the tricky part, and there may not be enough stock/material left for the grooves. Again not saying it can't be done, just may be more pracitcal to buy one off the shelf. Good luck.

 

If you have a machine shop in your garage and decide to make your own pulley, you might run into copyright issues with designs already on the market, if you post the results of your work that is.

 

^As long as you are not selling something copyrights have nothing to do with anything...you can make yourself anything you want as long as you are not selling it...

 

Good to know. I probably should have paid more attention in my business law class.

 

The way the factory pulley is designed (steel belt surface on a separate hub), it's not really possible - if you milled it down, there would be no pulley left. Might be possible with a JCW pulley (similar construction to aftermarket pulleys, although pressed on as well).

In reality, it would probably be easier for a machine shop to make a new pulley from scratch than to mill down an existing one.

It might be possible to reinstall the OE pulley by heating it up in an oven and slipping it on the S/C shaft, but I don't know of anyone who has done it. The oven would need to be literally right next to the S/C (either on or off the car) so as to keep the transfer time to an absolute minimum (like a few seconds at most). And if you didn't get the position right, you'd have to pull it off and start over.

 

To extend on my previous post, IanF is right in that it would probably be easier to make a new pulley. With a CNC lathe, you should be able to pop one of those puppies out in no time.

 

It's not quite that simple. Making a pulley from scratch would take many, many more hours that it's worth. There are some tricky little design aspects which make it more of a job than just popping out a pulley. For example, the angles of the grooves in the face of the pulley are acute, and require a special machining bit.

There is no copywright on pulleys, just ask JLM, a former NAM member who designed and made the original pulley. Many companies shamelessly copied (and in some cases improved upon) his original design.

Don't bother trying to machine the stock pulley. You'll bend it trying to get if off, and it's too thin.

Bottom line buck up for an existing pulley, many of us have already done the hard work and testing to make sure they're right.