Finally solved the persistant clicking problem
 

I had been dealing with ticking ticking ticking valves for months. I had narrowed it down to the #5 intake and could never make it tight enough to shut up. I finally took the car into my favorite wrench in Denver and they gave me the bad news. It seems somehow the cam lobe for the #5 intake got worn down. Maybe a failed oil squirt thing. Who knows. Crap. At least they will be doing the "while you are in there" as the engine has to come out.

My question is: how common is an eroded cam lobe?

Not very unless there is a ton of miles on it, like 500K or a defect or the wrong oil. What kind of oil are you using? is this the 84 or the 75?

That's not good. I hope they don't have any expensive surprises for you when they tear it down. :(

Good luck with the repair.

this is on the '84 with 122K miles on it. The wrench today told me that the little hole in the oil lubricator bar was plugged and that was why the cam lobe had worn down. Bummer. He checked the plugs to see if I was burning oil, which would indicate valve guide issues, and he said all of that looks great. He had done a compression test before he tore it down and that looked good as well. He said the engine looks good except for the cam. There are age related oil leaks that can be handled.