71B resto venting fuel tank

My venting fuel tank was shot. Replaced it with a new venting tank. The line from the tank to the canister in the trunk was shot. Can't seem to find anyone who sells a replacement. My question is can I fabricate a line to the canister and let the canister vent through the trunk floor without connecting it to the charcoal canister in the front. Do I need the front charcoal canister for connection to the engine? If so what purpose does the front charcoal canister serve? It would be easiest to vent to the rear canister and then let the canister vent out of the trunk floor with the existing line. The line to the front seems unnecessary. What am I missing? A lot of questions and any help would be appreciated.

On question is have you detoxed the engine or are you running all the smog crap?

Do NOT let the tank vent through the trunk. I accidentally did this - the rubber hose was cracked. I couldn't figure out where the smell of gasoline was coming from inside the car. You can't believe how much the smell would penetrate from the trunk to the cockpit.

Although you may be able to come up with a viable venting scheme, it is just as easy to fix the old hoses and go through the cannister.

When I redid my 72B I just capped the vent line from the tank, threw away the canister and put a vented gas cap on. I think the gas caps pre 70 were all vented.

Don, I am not running any of the smog gear. Does that help re the charcoal canister issue.

From what I understand the charcoal cannister under the bonnet and the vapor cannister in the boot are there primarily to re-circulate the gas fumes from the carbs and the fuel tank back into the fuel tank after they return to the liquid gas state. They're also there to vent the fuel tank. Technically they're not emissions equipment, from what I understand, but fuel vapor recovery equipment. I know the tappet cover is vented to the charcoal canister but don't really know what function that serves. It may be to pressurize the charcoal canister to drive the fumes back to the vapor canister but I think it's also also there to vent the crankcase. I'm sure those who know more than me will chime in.

Shawn Escue

I think all the venting hoses and charcoal filters are all part of the alleged smog control system. I'm with Brian on this one, cap it off and use a vented cap. As for the charcoal cannister up front I want to remove it and put a side pole battery where it is sitting.

Shawn you're close, the valve cover draws in through the cannisters so that some of that vapor can be burned in the engine.

My take is that if you've got a functioning anti-runon valve then hooking the carbon cannisters up correctly will allow the car to stop when you turn the key off. It also provides a relatively safe place to run the carburetor overflow to, as opposed to it dumping out onto your exhaust manifold.

Don, there's a very lengthy article (33,000 plus words!) that can be found on this site about "Tuning the 1800cc MGB". It talks about the emission control system in depth and comments something to the effect that if you're de-smogging the engine leave the canisters and their lines and hoses in place as they're not part of the pollution control system. That's where I'm getting my information. This article (more like a small book) is good reading for the MGB enthusiast as it is filled with usefull information about everything MGB engine related. I'm kicking myself these days because when, all those years ago, I de-smogged my car I took out both the canisters and the various hoses and lines. Now I'm in the process of trying to gather up all the required parts to re-install the vapor recovery system. I figure that there must be a good reason why the factory did it that way and, if it's not part of the polution controls, I'm going to make sure it's in my car. I figure that, if nothing else, it'll save me gasoline! Cheers!

Shawn Escue