Now I changed the pulley

[kappa67]

i all
Have a 2000 Pontiac grand Prix GTP.
Now I changed the pulley to a 8 Rib SFI Balancer.
When I'm driving all is good...if I stop the car makes a rattling noise from the engine.
What is this?
Something new??????

​thanks for your answers

[FordMan77]

Open the hood while it's running and use a mechaincs stethescope to try and pinpoint the noise. If it wasn't there before then re-check all the things you disturbed. Make sure everything is spinning true and not wobbling around.