Yeah, I bet the cam followers are the guilty party, if the tick quickly goes away when the pressure comes up. While you have the cam out, check the lobes very carefully. When cams fail, it's usually one or two lobes that just wear down, and you can spot it if you examine it very closely. But, again, not a lot of bad cams on the 103 mentioned in the forum.
Oh, also check the 3 little screws that hold the cam-oiler pipe above the cam.
I actually had one come out! If that pipe loosened it would starve the cam lobes for oil, and might dump a lot more oil in the area around some of the valve stems.

DG