BB Valve Clatter

[stope4]

Removed the intake manifold to clean it up and replace the gaskets. Now that the work is complete, my valves clatter when I am on the highway and accelerating. Timing is at 8 degrees btdc without vaccuum. When running, the vacuum advance is connected to ported vacuum under the throttle on the carberator (no vacuum at Idle). The valves did not clatter before the removal. I did not check what the timing was beforehand. Any suggestions?

I did a search and the answers are all over the place regarding ported and non ported vacuum. Which tells me, if my timing is set correctly, advance can be hooked to either ported or nonported. So, how do I know when vacuum is correct? Do I advance it or retard it? Do I leave it on ported or, do I go to nonported? I do not know how to measure mechanical advance.