What is the clanking noise under the hood?

What is the clanking noise under the hood? I have a 2006 Dodge Charger, that has recently started to clank. i took it to a mechanic friend of mine and he diagnosed it with crankshaft problems, but i dont think it is. its a 3.5 L V6 aluminum block. anyway, upon taking the manifold off it turned over without any noise at all. i really need to know what this is... it is my only way to work