collapsed lifter of wiped cam?

[slw.ohio]

This is my first BBC a 454. I started hearing a nasty ticking noise coming from under the valve cover, so i checked and adjusted the rocker arms. That didn't help I then noticed I wasn't getting oil out of one of the push rods. I talked to a couple local guys and they tell me it's probably a collapsed lifter or a lobe wiped from the cam. I don't really know where to start. Any info would be appreciated.