Charcoal canister routing

[Jake_C_]

Quick question guys, this is the charcoal canister I have
Obviously I have the vapor line from the tank hooked up the to port labeled “tank”. I assume the port labeled “air” with the cover over it is meant to be left alone? The “purge” port would go to a vacuum actuated purge valve with the vacuum line coming from the manifold vacuum on the carb (edelbrock 1405). I’ve heard of people running the outlet from the purge valve to a T on the pcv valve line, or running it up to the air cleaner. Is either one preferred? They would obviously serve the same purpose of getting vapor into the carb. Am I missing anything here? I previously had the purge port running directly to the manifold vacuum on the carb but realized that was wrong. Thanks in advance!

 

[Wes Harden]

Mine is plumed to ported vacuum on carb, no valve, stock q jet. I would have to test which port for the 1405

 

[Jake_C_]

Mine is plumed to ported vacuum on carb, no valve, stock q jet. I would have to test which port for the 1405

On the 1405 driver side is manifold, passenger side is ported. Interesting that yours vents to the carb at all times. Just curious did the stock carb setup use vacuum advance on the distributor?

 

[Wes Harden]

yes has vac advance. Q jet has more ports than 1405, Ported vacuum only draws the fumes from the canister when the throttle is open. With the q jet the passage might not be open until cruise circuit is in use. I haven't tested.

 

[Jake_C_]

yes has vac advance. Q jet has more ports than 1405, Ported vacuum only draws the fumes from the canister when the throttle is open. With the q jet the passage might not be open until cruise circuit is in use. I haven't tested.

Interesting, so here’s another question, does the charcoal canister hold vacuum?

 

[Wes Harden]

Not ours. Some of the more modern system can seal the canister.

 

[dyeager535]

GM might have gotten tricky when not using a purge valve on carbs and used one of the "timed" vacuum ports so it wasn't drawing all the time.

I would expect if that wasn't done, there would be a constant vacuum leak since the cannisters aren't sealed?

 

[Jake_C_]

GM might have gotten tricky when not using a purge valve on carbs and used one of the "timed" vacuum ports so it wasn't drawing all the time.

I would expect if that wasn't done, there would be a constant vacuum leak since the cannisters aren't sealed?

right, that’s what I was thinking, so hooking it directly to a manifold vacuum would basically be a vacuum leak.