Another Dumb Question :-) WEBER CARB

As I get past that last little road block I’m anticipating that I may have some time this weekend, some real time, to get into this build. The short block is done, and if I get the adjustable rocker assembly from C.I. this week I’ll have the long block completed. It would be nice to mock up as much as possible before it’s in the engine compartment and harder to work on. So I’m planning to install the carburetor (if only temporarily), DSII distributer, fuel pump headers and everything else that bolts on this thing! I do have a question for any Weber users that can answer, in the picture below I have labeled the fuel inlet, fuel return (plugged) and fuel filter. I believe the upper fitting goes to some sort of a vacuum canister? Can I just plug this or does it need to stay open? Or am I way off on what that fitting is for?

Thanks Bill

http://www.mazdatruckin.com/B2200/Carbu ... nstall.php

Look at Fig 2

Thanks Thad, that helps identify it for me but I’m still not sure how it plays into my application. I’ll figure it out or punt when the time comes. Things are progressing nicely with the adjustable rocker assembly on track to arrive tomorrow; maybe I’ll be able to get this engine back in the car this weekend or next. Thanks to all for all the help, this has been a very supportive forum and Classic Inlines website is a real treasure trove of information. There is still a lot to do but we can almost to see the finish line now.
Here’s where it’s at today.

My H/W 5200 doesn't have that, but here's my bet:

Check to see where the other end of the passage is, if it's just a bowl vent you should be able to cap it - assuming it's like mine where the bowl also vents inside the air cleaner area. If it's the only bowl vent there is, then you'll want to connect it to filtered air (anywhere between the air filter and carb throat oughta do).

Looks like on some applications it ties into the pcv line...which might make it a good source of filtered air to the pcv valve if it wouldn't try and suck fumes from right out of the float bowl and into the crankcase - if it draws from somewhere above the carb throat and the bowl, I'd think it'd work ok for that.

Here's a pic of mine, the red arrow is pointing to the bowl vent area - I'll bet that port of yours goes straight into there as well.

That motor looks good, nice job. I'll bet it goes good too.