By design, the Teapot 4V carbs will not indicate a vacuum signal for the distributor at idle.  It’s a combination of ported and venturi vacuum at the distributor port on the carburetor with the spark control valve being a part of that mix.  If you speed the engine up beyond idle, you should be able to pick up a vacuum signal at that port.  The higher the rpm, the greater the signal but at idle, there should be no vacuum present at that port.

Lorena, Texas (South of Waco)

Still chasing gremlins in the stock '54 Merc (with '55 teapot carb) and have a question regarding vacuum.  I have a new vacuum advance ordered and just checked the vacuum port on the carb to distributor and I am not detecting any vacuum signal.  I cannot get a reading on my test gauge nor can I feel any vacuum by pressing a finger into the hole.  I am reading 22 - 25 Hg from the manifold.at idle.  Is the signal to the distributor inherently low or do I have a restriction in the newly rebuilt carb?  Possibly with the spark control valve?   I have never monkeyed with a vacuum advance before and recently found that my current module is not holding any vacuum during a pump test but it does slightly move the breaker plate a bit with each pump stroke.