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My "fault" last year was switching the connection hoses so that the advance unit was seeing the full vacuum from the manifold and not the carb take off.
If you have a close look at a set of carbs the vac take off on the carb body is already restricted down at the base as the hole is only quite small. May gues is that with a vacuum gauge the restriction is about the same size - but the effect less as there is a lot more inertia in the weight of mercury, metal rod or whatever else yoiu use. The vac advance unit relies on spring force, and thats the oscillation problem.
As an experiment I think the movement could be damped by connecting to all carbs at once to the vac unit, but 1,3 & 4 will need a small bore restrictor making up.
I don't think the problem is in the units movement, but in the aging wires coping with it getting brittle. I's say a proper splice job should last another 20 years.
If you have a close look at a set of carbs the vac take off on the carb body is already restricted down at the base as the hole is only quite small. May gues is that with a vacuum gauge the restriction is about the same size - but the effect less as there is a lot more inertia in the weight of mercury, metal rod or whatever else yoiu use. The vac advance unit relies on spring force, and thats the oscillation problem.
As an experiment I think the movement could be damped by connecting to all carbs at once to the vac unit, but 1,3 & 4 will need a small bore restrictor making up.
I don't think the problem is in the units movement, but in the aging wires coping with it getting brittle. I's say a proper splice job should last another 20 years.