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.

[JimKshortstep4x4]

With the vacuum advance connected to port vacuum under acceleration the vacuum advance is fully advanced. Some vacuum advance units will move the timing 15 degrees or more.

I would try moving the vacuum advance hookup to the vacuum on idle port.

Jim

[dwaite72lnghrn]

It sounds like an air leak. Factory vacuum on a BBC points dizzy is full vacuum. Ported and full ports provide the same vacuum while going down the highway. Ported takes the advance off the dizzy while idling for emissions. I run full even with HEI as it stops the stumble off idle and did improve my MPG.
If you didn't have ping/rattle before you pulled it I would start looking for a vacuum leak. Did you take the carb off the intake?
Make sure all of the vacuum hoses are connected and not split.