Cruise control on a stock 3tc?

[builder]

I have installed a cruise control on my stock 3tc, but I am only seeing 12 inches vacuum during highway driving on the ports I have tried. Is this normal or is there a better vacuum port to use? I see 19 inches at idle which is within spec, but drops down to 12 on the highway. The setup works but is slow to engage. both ports were at the base of the manifold.

[BOBLOOK]

Spring Control Actuator vacuum to stiff

Missing the vacuum can or actuator

Did you try vacuum before the carb butterfly?

[builder]

The can helps a bit, and a proper one-way valve seems to help too. Tried the ported vacuum for the distributor, not much difference when it counts. The biggest help seems to be a port with good flow, there were other ports with the same vacuum strength but less flow. The control box might be giving a certain amount of slew, or it's just not aggressive enough. it's a factory unit and there is no adjustment.