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.