1999 Dodge Durango Engine knock

Have owned for 6 mos. Took to so. Calif. And it just lost power. Pulled over and it overheated. Wouldn't start. 2nd garage got it started. Had it transported back to Oregon. Got it started but now:
if sits for a day when started it knocks very loud for 15+/- seconds and quiets down. Then after a while you can hear a definite knock on both sides of engine thus making the noise coming from somewhere in the center of engine.
Shut it off and wait 10 mins, start it and no knock for a while. Then same knock.
Oil is dark and end of dipstick has a very hard crust about 3/4" up the stick, almost like burnt on oil.