Those with centrifugal superchargers and no A/C...

The idler pulley sound about right just get the next smaller sized belt to pervent the tentioner from maxing out and pushing the belt down to the water pulley.

Also double then triple check and make shure you have the belt routed right.
 
Same problem no a/c. I added an extra idler pulley to one of the brackets to hold the belt up off the water pump.

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