[ghall]

Well color me shocked. I took your advice and let my SVX sit idling for more than hour. To be honest, I was doubtful that it would make a difference since I had already tried SeaFoam. But, after about an hour, the knock gradually dissipated and eventually disappeared. I was surprised, but elated. My guess is that it was a stuck lifter that gradually "unstuck". Many thanks for your suggestion!!
Regards,
Gary