Take an old belt and cut it in half. Put the end of the belt in the vee of the pullies. if it bottoms in one of the pulies that pully is worn.
If it bottoms in all of them the belt is to narrow. Remanufactured alternators use the old pullies. some are 40 + years old. They do wear as do the other pullies.
Most of the times you hear a belt sqeal on start up it is due to a narrow belt bought at Advanced or Autozone combined with a worn Pully on a reman Alternator from the same place.
Over tightening the belt just causes more problems.
I fought the samething and I only have two pullies on my car. My belt was also turning upside down at over 7500 RPM's. All I did was go to a wider belt. I have hardly any tension on the belt now.
I can leave my alternator turned on, on start up and it don't sqeal. Mine also sqealed when started with the aternator turned off when turning it on while running . you could turn the switsh off and on while running and make it sqeal a couple of times. until the bellt got hot.
if you look at the pics above you will see I even added an adjustable sleeve to keep making tension adjustments when I was fighting this.
Just get a good belt and check your pullies.
