Timing Question
 

Im trying to time my street ported 12a after putting on the racing beat holly carb and intake. I got the leading timed in but for some reason I cannot get the trailing mark to get close to the needle although it is in the general ball park (I can see it moving ). The engine has no change in idle speed or roughness as I fully advance and retard the trailing diaphragm. Is this normal?

How is the vacuum advance routed up? If its routed into manifold vacuum it is under constant full advance. Try disconnecting the vacuum line and see if the timing mark becomes visible again. You are getting Trailing spark right?