How do you check valve lift?

The popping noise wasn't there until I started this process, so I would guess thats not it.

Update -
I rechecked the valves with the engine warm (two exhaust where a barely tight), checked the points (OK) and reset the timing. Its still jumping around between 16 and 20 degrees but that maybe due to the idle being high. I then readjusted the carbs and was able to get a rough idle at 1000. That was last night. Then this morning it wouldn't start (it was about 45 degrees burrr - At least here in CA :-) Just crank, not even pretend it was going to start. I will try again on Saturday when it should be warmer.

I'm pretty sure its not the carbs. I "refreashed" the carbs a few months ago and they have been working pretty good. Also my (limited) experience with them is that they will usually let me start the car unless they are too lean (I've read everything I can find on the net including the things at vclassics, thanks they have been really helpful with the carbs, I'm not afraid of them any more)

I have not checked the centrifugal advance free and returning properly (per Rons suggestion, not sure how) but I did see the timing advance with engine speed. Also I have not taken a file to by feeler gauges yet to get the "necked down feeler gauge". I have managed to adjust the valves correctly before (about a year or so ago) so I am pretty sure its not the valves, but something with the ignition.

I'm no master mechanic, but I think I've got things pretty close (I'm sure closer to specs then they where). It seems like it should at least start. I'm wondering if I got a bad cam or timing thing-a-ma-ghig or need a head job and now the factory settings no longer apply. The engine has at least 37K miles on it (I'm the 3rd or 4th owner so I don't know how many times its been turned over) I also don't know the history of the motor, except the the previous owner did nothing major to it.

Just had a thought, if I can only get it to idle at 1200 should I still set the timing to 16 degrees, or should it be more like 20+? I'm thinking that the 16 degrees is for a 700 rpm idle.

Thank
shane