Question on Dual Carb vacuum

The secondaries are pulled open by increased air flow, with rpm, thru the venturies creating vacuum at a small port just above the booster area. They act independent of engine vacuum. No manifold vacuum signal needed.

It would be a good idea to reference the two pods together so both carb secondaries open simutainiously. You can use a kit, like below, with a piece of vacuum hose between the two, to accomplish that.........

http://www.summitracing.com/parts/hly-20-73/overview/