Pontiac Repair: engine noise, grand prix gtp, belt pulleys

Question
Hi I have a 1997 Grand Prix GTP engine type 1 we have developed a loud uneven clattering noise, seems to be from lower front of engine at an idle, when driving it disappears.
Have removed super charger belt, still noisy, removed main drive belt noise gone.
Replaced that belt and tentioner pulley did not fix problem.

   Thanks Dave

Answer
Hi Dave:

can you put a long shanged screwdriver on each of the drive belt pulleys and narrow the noise do that way if you put the screwdriver on the component and the other end to your ear you will be able to find the noise that way. It may be the harmonic balancer there is a rubber sleeve between the hub that attaches it to the crank and the pulley that the belt rides on that pulley may be cucking on the hub with thebn belt on it but not when it's off. The water pumps those were noted to go too you would be able to feel that with the belt off turn the puklley by hand or see if it has any play up and down or in and out. with out seeing it or hearing it I can only guess. Good luck :-)