when i turn the truck on i hear a loud noise that almost makes the truck sound like a diesel. it goes away after a while of idling or driving. I've been told a few things (exhaust manifold, catalytic converter, or cam/crank shaft positioning.) i posted a short video on youtube (below) so you can hear what I'm hearing.

2005 ram 1500 187k miles

 

The problem about cameras and recordings is that each mic can make a sound, well, sound different and hard to tell where it is coming from. But my vote are the valves.