Guys

I'm redoing the fuel lines from the rear mounted gas tank to the engine mounted fuel pump on my 72 chevy and I have a question.

I cut out and removed all the emission and vapor canister lines that connected to the fuel tank because I didn't want them in the way and they were probably trashed and rusted through anyway.

My question is - Is the fuel tank supposed to be vented to atmosphere somehow? (probably through some emission device right?) If the fuel filler cap is air tight, which it is, and the fuel line will be sealed up as long as the floats in the carb are at level, where does the pressure go inside the tank when the temperatures rise and the air expands. Is there supposed to be a pressure relief strategy or what?

I will begin the fuel line portion of my upgrades next weekend and want to plan ahead. I need your help.

Please explain.

Lee

The fuel tank is vented to a charcoal canister behind the back seat. The rear canister is evacuated via engine vacuum thru the front charcoal canister.

The tank is not vented to atmosphere.

ok fine,

but...............

do I care about emissions? I guess I don't.

I just want to make sure the tank is vented so it works properly, don't really care about emissions. It's a weekend warrior car - not a daily driver. What can I do to vent the tank without all that emission crap? Can I just get a vented gas cap and be done with it or does that present it's own problems.

Why not just replace the hose from the tank to the canister. I don't give a hoot about emissions either but all you need is one short "Fuel Vapor" hose and a couple hose clamps and you're set.

Leaving that tank vent open will guarantee that you'll dump gas out of its orifice when you have a full tank. You have to cap it anyway, might as well hook it up to your canister and your problem will be solved AND your tank will be properly vented too.

Its not like its a tough job!

Why not just replace the hose from the tank to the canister. I don't give a hoot about emissions either but all you need is one short "Fuel Vapor" hose and a couple hose clamps and you're set.

Leaving that tank vent open will guarantee that you'll dump gas out of its orifice when you have a full tank. You have to cap it anyway, might as well hook it up to your canister and your problem will be solved AND your tank will be properly vented too.

Its not like its a tough job!

yea - sounds logical and correct. I have another question though. Is the canister vented to atmosphere somehow? If I pipe the gas tank to the canister - how is it ultimately vented to relieve pressure?

The fuel tank is vented to a charcoal canister behind the back seat. The rear canister is evacuated via engine vacuum thru the front charcoal canister.

The tank is not vented to atmosphere.

Oh wait, just remembered you're earlier response about the canister and manifold vacuum.

I am definitely "NOT" running an emission line from the rear charcoal canister to the engine compartment for venting - there has got to be a better way. Can't I just vent to rear charcoal canister to atmosphere (leave that connection open) and solve my problem?

vent gas fumes into the trunk or interior of your car?????:(

the 64's were vented with a tube that went up through the trunk floor and then returned back down to bottom, that way it allowed pressure to not build up or vacuum for that matter, but kept the fumes outside. I would say keep the canister in the trunk, and then put a piece of tubing back out of the trunk following the original path to the fram or body or wherever.