Take a long screwdriver or other long object and use it as a stethoscope. Stick one end up to your ear and the other to different spots around the engine. You can at least narrow the noise to a certain area. Just be careful around the moving parts of course.

I have had one 350 Chevy have one of the nylon coatings break off of a cam gear tooth and get stuck in the timing chain. It then hits the timing cover. But that was a pretty solid knock more than a tick.