Strange Exhaust sound

Does it have a smooth idle? I had a friend with a '74 chevy truck (pos) that had a crazy metallic exhaust noise that ended up being a bent exhaust valve that ended up falling in the cylinder and destroying the bore, so it basically killed the engine. (this was of course after he wrapped the heck out of it going up a dirt hill several times and driving it home). It's probably not what it is, though. the exhaust systems of both vehicles should be identical, so it's anyones guess what it is without more info. Good luck