Catastrophic Failure of the Camshaft Bearings
Took the Dart to a shop here in the area and they weren't able to determine the reason it was running so roughly at idle, so I took it to another place a friend recommended. The guy at the 2nd place had it two days before he called me and said he believed it was a camshaft issue. When he went to remove it, he and another guy had to use a pry bar to get it out of the engine. Once it was removed, he took the top components off the motor and realized the camshaft bearings had disintegrated, and of course, the bits and pieces thereof were now scattered throughout the 340.
He pulled the engine and later this week we're taking it back to the shop which rebuilt it two years and 1,900 miles ago. I called them and told them what had occurred, and they're standing behind their work. They're going to tear it down to see what happened, and go from there.