Distributor venting system questions (1 Viewer)

[Captron]

1st post.

I recently pulled the air cleaner housing from my desmogged ‘84 2F engine and forgot how to put the vac lines back together. Thanks to this great site I figured out how things are supposed to be. My current set-up is a manual choke Rochester carb (7012452 used on 55-58 Chevy) without any of the vac ports found with the Aisin carb. The vac line from the intake manifold to the VCV was cut and sealed off so I don’t think my dizzy is properly ventilated. I’m considering reinstating the VCV but I have two questions:

1. Do the unwanted fumes that fill the dizzy come through the dizzy/engine seal or the vac advance lines originating from the intake manifold?
   
2. Why is the VCV even necessary (ie, why not just run a vac tube straight from the dizzy to the air cleaner housing)?
   

 

[Random Dan]

I replaced my factory points dissy with an electronic ignition one from a US truck. I just ran one line to the air cleaner for the light vacuum and the other to an filter in the firewall. The electronic ignition itself produces corrosive gas and that's why you need to draw in fresh air.

 

[Output Shaft]

This thread has more info:

Distributor cap vent VCV issue

 

[Captron]

Man thanks! I had read the thread you linked to previously but somehow I didn't connect the creation of ozone because of the spark. Makes sense now. The is VCV being used to prevent backflow of fumes evaporating off the carb into the air cleaner housing and down the dizzy vent tube. I need to check when I get home but I think the carb bowl has a flapper that is open to atmosphere when either idling or engine off. But I might have that backwards in my head. If the flapper is setup to vent fumes from the carb bowl then wouldn't this render the VCV pointless?

 

[Output Shaft]

The VCV also prevents moisture (humid air) from back flowing and condensing in the distributor when the engine is shut down in an attempt to minimize corrosion.

The left over ozone in the cap at shut down, along with any moisture that enters, creates a virulent corrosive environment.

 

[Captron]

That makes a lot of sense. I will check to see if my VCV is still functional and reconnect it if it works. I will probably replace if the VCV is shot.
Thanks for the help!

 

[Captron]

Update:
Vcv works. I bypassed it until new vac lines came in. I was surprised to have a "micro explosion" in the dizzy that sent a visible puff of smoke/dust into the cabin. Characteristic match stick smell. I got my vac lines in and hooked the vcv back up. Seems to be running well now. Thanks for the help! ( on to the next problem)...