HelpI started the car up this morning, seemed louder than normal, but thought it was the change in weather and drove to work. It ran normal no problems, but when I pulled in the garage tonight there is a terrible noise coming from the front of the engine.

Took off the valve cover thinking the chain was about to go, but the chain is tight, in that I can't lift it off the gear. Where is the noise coming from and should I be concerned, as I need the car tomorrow. Could the vacuum pump make this much noise?
PeterG