Try fitting a larger-diameter pulley to the alternator, if you can find one. Sometimes the belt contact area around the pulley isn't sufficient for the belt to get enough traction. If the crankshaft pulley is very large in relation to the alternator pulley, it might be trying to drive the armature too fast. A glazed belt surface is another possibility, if the squeal has been going on for some time.

How much of the belt is wrapped around the alternator pulley? If you install a longer belt and a longer adjuster bracket, there will be more belt wrapped around the pulley, which translates to more traction.
Jerry


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