what timing belt? these cars have a timing CHAIN. you should get a new timing chain and dampner every 100k miles or so if you are one to do preventative maintenance. there have been a billion grand prixs that have gone well over 150k miles without changing them though.

once the dampner breaks then it eats the chain and it will snap. then youll have bent valves and scuffed pistons after the motor free wheels for a second.