Charcoal Can

[germando]

Hey all getting ready to put the 454 back in my 73 GMC and guess I need to address this issue. When I took everything apart the fuel line to the can was fine, but the other two lines were literally just tucked down inside the fender. Where do the two live from the can go?

G

 

[fast 99]

Try looking at the vacuum diagrams on this site. Should narrow it down a bit.

 

[75gmck25]

GM seemed to change the vapor recovery design multiple times over the years, and for your ‘73 the original vacuum diagram may have been on the air cleaner, not the radiator support. The diagram is often missing.

My ‘75 350 has a two port canister, and the 2nd line just ran to a dedicated port on the ‘75 Quadrajet. When that port was open, it pulled air from the canister. Apparently the carburetor port controlled all the venting, but my newer Quadrajet does not have that port. I have tried just connecting the canister vent line to the PCV hose with a T and it seems to work fine, and there are also PCV valves with two ports.

However, many other trucks seem to have an additional port on the vaporcanister, and a vacuum control or valve only opens the venting under certain vacuum conditions.

 

[germando]

I finally found a diagram for a 3 port can on autozone of all places. So for anyone else looking for this the original routing is 1 port from the fuel tank. 1 port goes to the pcv valve and the other went to the port on the front of the qj carb.
So since mine wasn’t used to begin with I will leave the 2 ports open to vent and run a line from the pcv valve to the port on my Edelbrock carb

G
PS. Autozone has some nice diagrams available if you make a user account there