Pontiac Problems? Ask a Mechanic for Answers ASAP
It sounds like you may have a timing chain loose for some reason. The area and sound you describe are consistent with that. It could be the tensioner has collapsed or a guide may have broken, because it should not be worn out and there is no regular adjustment needed. If the noise changes as you rev the engine in neutral and then let it idle back down again, that is most likely the cause. I would not wait long before addressing it because if it skips and comes out of time it can ruin the engine.