[cleszkie]

Are you running the correct width belt? If you run a belt that is too narrow, it will go all the way to the bottom of the pulley V-groove, and make contact with the flat bottom of the groove. No amount of tightening of the belt will get rid of the noise now that the belt tension is no longer controlled by the tapered side of the pulley groove on the side of the belt, but rather the flat bottom of belt against flat bottom of groove. I had this issue with a custom built alternator, and swore up and down that the alternator had a bad bearing. Put a wider belt on it that didn't touch the bottom of the pulley groove and it has been silent ever since.