1999 Engine loud noise after chatter sound

My engine (2.4L 4 cyl) was making a low chatter noise that sounded like I got some bad, low octane, gas. That lasted for two days. Very low sound that I thought was coming from the top of the engine. The following day, the noise became a loud noise that increased in sound as the engine was reved. A loud low-tone clanking noise that seemed to be coming from the top and bottom of the engine. Any ideas how to test or diagnose this problem? I have some loss of power, but no other signs of a problem except for the clanking noise...

How is your fluid levels? Oil, coolant.

How is your fluid levels? Oil, coolant.


All is fine with my levels. No water in the oil side. No oil in the
coolant side. No smoke. Quick start. Just a loud noise that appears
to be coming around the left side rear of the overhead cam.