Gas tank vents

[jpane]

When I bought my current Europa years ago, it no longer had the large "catch tank" canister across the top of the firewall. I am having the car reassembled after a long dormancy, and don't remember a lot of details. I have new, aluminum  tanks, I think a group buy organized by Steve Veris. The tanks have vent fitting for tubing to go to that missing catch tank. I do have the charcoal canister that sits on the left side of the engine compartment, though I don't remember how or whether it was hooked up. Can I run the vent tubes from the tank to that canister, or just leave the tubes open?
I confess I already have the crankcase breath venting to the atmosphere.
Thanks, John

[jbcollier]

You could run small hoses first up and then back down and then leave them open.  The hoses need to go higher than the highest fill level in the tank/filler assembly.

Myself, I would plug the hoses and fit fuel tank caps with built in breather holes.

[Sparkrite]

What exactly is the large "catch tank" canister across the top of the firewall for. I assumed it was for the American market as I have seen so many images where its missing.

[jpane]

It was a Federal emissions piece. I’m not sure what it was for exactly, it seems too large to catch overflow when filling, but the parts manual calls it a catch tank. But perhaps regulations assumed worst case scenarios.

[Pfreen]

On my tcs, the the fliptop fillers have vent tubes.  I did not like leaving them open, which is what it was like when I bought it.

If you flip over and survive, then you get to see how much fuel was in the gas tanks as it pours all over the ground.

I did not like that so I "t"d the two tank vents together feeding a gas tank vent valve (see attached photo).  If you flip, the valve shuts off and the gas stays in the tank.  Right side up and it is open to vent the tanks.

My car doesn't have the charcoal filter, but if you attached the vent valve to the outlet side of the filter, you should be flip protected.

I actually think the giant catch tank originally used was to prevent spilled fuel caused from over filling the gas tanks going into and contaminating the charcoal filter

I do not know of another car of the era with such a giant catch tank so that is all I can think is its purpose.

[Kendo]

I agree with Pfreen that the large tank was to keep liquid fuel out of the charcoal cannister. I don't have any of that gear in my Federal TCS, but was researching systems to see if I should add it back. My car had a lot of gas fumes in the garage I wanted to eliminate.

Pfreen, do you have a model number for that gas tank valve you showed? I looked all over for something that wasn't weirdly designed to fit into a weird corner of some mass-produced car. No luck.

[Pfreen]

Here you go.

https://www.summitracing.com/parts/tnk-vvr?seid=srese1&gclid=Cj0KCQiAmL-ABhDFARIsAKywVads2WFWojtBcloCMDvk46XNZN6PU68Z1MsfjHE232lsRh1I_jJfhyUaAkLUEALw_wcB

[BDA]

How about this one? https://www.ebay.com/itm/Gas-Fuel-Tank-GAS-Cap-Valve-Vent-Breather-Hose-Black-Tube-CNC-ATV-Dirt-Bike-BLUE/262351825082?hash=item3d156328ba:g:aPEAAOSwze9clEpC

[Nisswa Collision]

I always assumed the big tank was just a vacuum tank to power the Evaporative Emission Control System required from 1971 on. I don't have to get my cars emissions inspected, but the last time I did, they did the underhood inspection. What they saw had to match the picture on their computer or you couldn't pass until it did. It was big things like that tank that would red-flag you. Don't they still do that? It's gone on my car.

[BDA]

It depends on your state. When I first got my car on the road, a safety inspection was required. They even complained that I had an exhaust leak because of the slip fit between the secondary header tubes and exhaust pipe (it didn’t matter that there was no chance it could leak into the cabin.) I don’t think they ever tested my exhaust. They had no idea what it was supposed to look like so that wasn’t an issue. Later on, they loosened the regulations and my car no longer needs any inspection.

A lot of states grandfathers cars older than 1975 or some such. Check for that and you might also check how they treat modified cars, kit cars, or hot rods. If you have enough modifications, your car may fit in one of those categories.

[jpane]

The small hose with filter that BDA posted looks like a cheap and simple solution. Any idea of the diameter of that hose, or can that be easily adapted to the gas tank vent?

[BDA]

I checked a few ebay listings for that and similar valves. None of them said what size tubing they used. I'm guessing probably about 1/4" ID but it may be worth a message to the vendor you choose. There are lots of people selling them just search for "gas cap air vent" or "gas tank air vent." I would also recommend a separate valve for each tank, if you have two, since they are intended for dirt bikes which wouldn't need as big a valve as a car would.

Edit: further looking found one that said the ID of the tube was 0.2". I suspect they are all the same.