Funny thing, but plastic vacuum tubing doesn't need a lot of clamping. Unless it's worn, it's sort of self-sealing. The opposite of pressure tubing, obviously. E.g. the intestinal mass of vacuum tubes in my old BMW engine just all lightly connects with finger pressure, but the car sure won't run if there's any kind of leak. It leaves me feeling sort of insecure. On the other hand, the copper tube fitting connecting the carb to the manifold on my A4 had come loose and wasn't making any connection at all, yet it kept cranking away.
I haven't had a lot of engine hours since I installed the vacuum gauge. FWIW, I did motor for a couple of hours during a mini-cruise this week and noted 10" cruising at 1500 RPM with a rather dirty bottom. Will try to remember to collect some more data.
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