carburetor port question

[redstone65]

I have these ports on my carb (pink arrows). Any idea what they are for? They seem to just pass through to each other.

Also, is the port with the green arrow the correct port for the dizzy vacuum advance?

[1972hiboy]

the pink arrows show the filtered fresh air port that supplies filtered air to the exhaust manifold then comes back up to the hot air choke. since the hot air choke pulls warmed air from the exhaust manifold you dont want it sucking unfiltered air into the engine. the green arrow is the correct timed vacuum port for the distributor advance.

[redstone65]

the pink arrows show the filtered fresh air port that supplies filtered air to the exhaust manifold then comes back up to the hot air choke. since the hot air choke pulls warmed air from the exhaust manifold you dont want it sucking unfiltered air into the engine. the green arrow is the correct timed vacuum port for the distributor advance.

Thanks!

Just for completeness, can you give me an idea of where these other ports are supposed to be connected?

Currently not connected:


Currently capped off:


Currently hooked to manifold vacuum:

[1972hiboy]

Good morning Dave. I'll address your question in order of the pictures. generally however all three things here are emissions related and makes me thing this engine came from a later year. I dont know exactly what and how all three of these connect up where they are supposed to, but I can give you a general idea. If getting your emissions system back up and working is what your after I would be happy to spend the time to look everything up. The first is connected to the fuel bowl vent, so I would assume that's for part of the EVAP system, probably purge back to intake port. The second is a live vacuum source most likely for supplying thermostatic switches. The third is your EGR ( exhaust Gas Recirculation valve ). And it usually tied into a spring/vacuum switch to sense driving at a certain throttle application because they are only supposed to bleed exhaust gas back into the intake under certain under light load scenarios. If emissions are something you don't need to worry, I would just cap these three things.

[redstone65]

Thank you so much. Definitely not restoring the emissions stuff. And you’re right. The engine is from a ‘74. I’ll post a pic with all the ports labeled for posterity.