Had my van to 2 garages and they both of opinion I had a lower engine knock ( 3.3 L). Definately sounded like metal on metal.
Finally brought to a Dodge dealer who informed me it was the serpentine belt (had a large chunk out of it). Even they said it can create was sounds like an engine knock.
A nice ending to this story which I thought I'd share with my resourceful friends on the newsgroups.