When trying to find stuff like that, I use my stethoscope -- just one from the auto parts store. ...
Indeed, stethoscopes are really useful for this sort of diagnosis and don't cost a lot. You can also use the method my Dad taught me... use a long screwdriver and put your ear up to it, moving it around until you get to the loudest area. With both methods, however, mind you stay
well clear of belts and pulleys... having the stethoscope ripped off your head can hurt, and so can a flying screwdriver.
Grooves from the valve stems can form in the valve rockers which give added clearance to the lash even though you set the valve lash according to factory procedure.
When the engine ticks, its usually valve lash.
If you don't have a "ClickAdjust" tool (Google it), then the best way I've found to precisely get a proper adjustment on cupped rockers is to simply use a dial indicator... set it up as close as you can to the contact point on the back of the rocker. Works fine. Of course, the real fix is to have the rockers resurfaced/re-profiled, and most cam grinders (Delta, etc.) can do it for you rather inexpensively.
And whereas I do agree that most often a 'tick' is from a valve clearance issue, I have, however, heard a very similar sound come from valve damage (burned valve or seat) where the 'tick' is actually the sound made by the blow-by during the power stroke (thus both sound like they are 'cam speed' because it only happens on every 4th stroke). The difference is subtle... the valve lash problem is slightly more sharp or 'metallic' sounding, whereas the blow-by lacks that sharp element. However, to an inexperience ear - or indeed, sometimes even an experienced one - they can sound very similar and listening to either problem via stethoscope (or screwdriver) will pretty much land you at the same place on the motor. You can diagnose the valve blow-by by pulling the spark plug for each cylinder, one by one, and see if the sound changes or if it disappears altogether... if so, you've very likely got yourself a bad valve or seat. Absolute diagnosis can be done by pressurizing the cylinder with compressed air, whilst both valves are closed for that cylinder, and listening at the intake and exhaust for 'hissing' air as it leaks past the valve.
