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By Lanny White - 3 Years Ago
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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.
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By Ted - 3 Years Ago
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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.
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