John, "at idle, making clicking, clunking sometimes rather scary noises. Typically, noises there will go away as the engine is revved up" this is a great description of the symptoms I'm experiencing. The noise is the loudest at idle but under load, especially on the freeway, the noise is absent. I also believe that this is accurate because when I turned the engine over by hand to adjust the valves at the crank shaft bolt I heard a clicking noise if I reversed direction. thanks for your help.