Mine sounds normal when idling. Doesn't sound anything like that, but, my bent rod was doing the circle dance like yours was.:D I've been driving it for over a year and it only started doing this a week ago. My truck has sat for a very long time though, prior to me driving it. It's had about 3000 miles or so put on it since 1987, so it was used very little since. The valve springs and rocker arms are all moving as they should though, so I dont think one of my valves is stuck...at least I hope not.