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TR6 Carb Vacuum Port- TR6 Zenith-Stromberg Carbs


This may be a dumb question; but humor me. How can I tell if the vacuum port on the top of my rear carb is working or is plugged; and how can I check it?



Great Pumpkin - R.I.P
On top would be an advance port (I think), so hook up a vacuum gauge where you can see it while driving and take a drive. Steady cruise should produce somewhere around 12-18 inches IIRC. Very dependent on throttle position, though. The value will drop if you try to accelerate at all, rise if you back off slightly, then go back to zero if you take your foot off all the way.


Country flag
If there is a nipple screwed into the hole and you unscrew it you may be able to see a hole about the size of a window screen wire in the dead center of the bottom of the hole leading to the throat of the carb....When the throttle disc is in idle position that hole will probably be covered by the rim of the throttle disc...which is why it reacts as Randall described.
There are quite a few carbs in the early 70's that had threaded blind holes in that location, either left over from vacuum Advance years or in anticipation of the EGR valve in future years.
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