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TR6 Carb Vacuum Port- TR6 Zenith-Stromberg Carbs

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TR6Dan

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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?

Thanks,
Dan
 
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.
 
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.
 
poolboy said:
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.
Click to expand...
While on the subject… I can’t figure out what this is… I have 3 carbs and one has a very sticky little piston and one has that adjustment screw backed out all the way. Thoughts?
 

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That's the type of transition valve for the float chamber vents that was found on the carbs for the 73 and 73 only carbs...Devised to make use of the Anti-Run on-Valve.
The system was greatly improved in 74 and retained thru the end of production of the carbureted TR6's
TR6 1973 emission valve.jpg
 
Rear port drilled.jpg

I'm working on swapping out to vacuum advance, have the same question. I'm assuming that this is correctly drilled through.
 
Take a look at where the hole comes out in the carb's throat when the throttle disc is in the idle position.
This should help:
 
Thats exactly what I needed, thank you! I held a light up to the inlet and could see the light through the port with the throttle closed, and not with it open. So I'm good to go.
 
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