3800 engine chirping

I have a 2001 Pontiac Grand Prix with 135,000 miles. It has the 3800 v6, no super charger. The motor has developed a chirping sound. The noise only starts after the engine is hot. At first I suspected a bad water pump or some drive belt accessory but the noise is still there after I remove the serpentine belt. The noise sounds like a bad bearing. Is this likely to be a timing chain issue? What other part could cause this behavior? The oil has been changed at regular intervals and is dinosaur oil, not synthetic. Thanks for any help, Terry