on a carb ported vac is when the vac is puled above the throttle plate ( no vac at idle) when you plug into the carb outlet below the throttle plate (vac at idle) it is call manifold vac because it has vac all the time. He is not talking about hooking your dist to a vac port on the intake itself.
Been there, Done that, Hope to live long enough to do it again.
Big Bill
I.I.# 4698
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