Something doesn't sound right!

A valve tap will have a unique sound that is clicking faster than a rod knock at idle. Usually a "knock" will sound like a knock, but the repetition is less than a "tap" of a valve. I once took a noise diagnosis class when I was a professional auto tech. You start thinking about RPM's and frequencies of the noise of moving parts and that isolates you to the right area to look. A story: a friend had a 70 Sport Satellite with a 383. I was at his garage, he said "man I think my motor is toast" He started it up, it popped pretty regular out of the carb. I said "pull the valve cover, that's in the valve train". We pulled the valve cover and one of the adjustable pushrods backed off to the point that the rocker was I/4 turned and not contacting the pushrod. In effect not even opening the valve. He put it back on and adjusted it, and it ran. But I always wondered why it fell off or backed off. I run the stock rocker shafts, as my cars are street only or "stock". I don't know if Mopars like adjustable valvetrains. It as if they weren't designed for it, something with the valvetrain geometry.