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70 b body gas tank vent lines?

luis9995

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My 70 b body leaked a little gas when parked on incline. Of the two lines at the end one goes into the trunk the other is small. Would it be ok if I block off the small one ?
 
One is supposed to be a vent line and one is a return line. If you're not using a return line then cap it off. 70 was supposed to have a 1/4" return line.
 
Hmmmm, my '70 never had a return line, so maybe that's a California emission thing???

I believe the big loop that goes into the trunk is an expansion tube or something like that (?). The little short line, about 6" long & bent, is the tank vent. It is attached with one screw & a tiny bracket at the rear shock absorber upper bracket.

I would not block that one off since in '70 the gas caps are non-vented. Under high fuel demand, it could cause the engine to starve for fuel and/or collapse the gas tank. If it's THAT one that's leaking, just check the hose and/or bend another one (in my opinion). If you do plug it off, make sure you have a vented gas cap.

Hope This Helps!
 
The one that goes into the trunk is a vent for the front of the tank the little j-shaped one is a vent for the back of the tank, if you have a return line it would be in the gas sending unit, six packs and hemi had the return

I capped both but I made a vented gas cap
 
The one that goes into the trunk is a vent for the front of the tank the little j-shaped one is a vent for the back of the tank, if you have a return line it would be in the gas sending unit, six packs and hemi had the return

And California cars had a return too. The CA cars have a "tube" in the trunk on the passenger side. This is a fuel capture device that has 5 lines coming out from it. One connects to the engine, and the others go to the special California gas tank.
 
And California cars had a return too. The CA cars have a "tube" in the trunk on the passenger side. This is a fuel capture device that has 5 lines coming out from it. One connects to the engine, and the others go to the special California gas tank.
Yes California tanks are a whole nuther monster with that big tube in the trunk and all the lines going into it
 
My Superbird 440-4bbl has a return line and 440+6 is right the return line is at the sending unit. The line that goes into the trunk is the vent line. I guess my repro tank has no other vent, of course I finished its restoration in 04.
 
My 440-4 Bird has a return line.. and it returns in the sender. Vent line to trunk/frame rail and another small vent to shock mount. Vents are the same as my '69 Bee which doesn't have a return line to the sender.

As noted by 440+6 the trunk vent is for the front of the tank and the small vent to shock mount bulkhead is for the rear of the tank. Maybe the OP's lines are hooked up backwards and the little vent is hooked to the tank front line.

Tank vent tube closest to sender should be the trunk line (front of tank) and furthest over the short vent tube that connects to the internal tube to the rear of the tank.

beerestoration2018 157.JPG beerestoration2018 158.JPG beerestoration2018 163.JPG
 
The long vent tube that goes into the trunk should be attached to the short line in the tank. The short "J" tube connects to the long line in the tank. Some of the reproduction tanks reversed the tubes in the tank so if this is not original, that could be the issue. The only way to know for sure is to take a light and look in the tank. I guess you could reverse what you have and see if that cures the problem.
The car has a non vented cap. Don't plug those vent lines unless you can find a vented cap that will work!
 
Yes California tanks are a whole nuther monster with that big tube in the trunk and all the lines going into it
I have the California gas tank here in Bossier City, Louisiana... I'm fixing to drop and replace my original tank. I've been wondering where all those hoses go. I bought about 20 feet of 1/4 and 3/8s fuel line to replace all that crap! I'm about to make the jump to TB Fuel Injection. I'll be asking questions about that project.
 
I have the California gas tank here in Bossier City, Louisiana... I'm fixing to drop and replace my original tank. I've been wondering where all those hoses go. I bought about 20 feet of 1/4 and 3/8s fuel line to replace all that crap! I'm about to make the jump to TB Fuel Injection. I'll be asking questions about that project.

The CA tanks have four vent lines that connect to the trunk mounted cylinder. These are short runs just between the edge of the tank and the four lines that protrude from thee cylinder. The other cylinder line connects to the breather cap on the engine, which in turn connects to the carb. Below are some pictures of my car before it was restored. Hope this helps...

Hawk


Engine bay (no engine) showing the vent line
IMG_1940.JPG



Vent Cylinder in trunk, viewed from below. The connected line is the vent from the engine. The other four go to the tank
IMG_1780.JPG



An original CA tank. Spectra still makes reproductions of these.
IMG_1569.JPG


Engine picture showing breather with vent line going to the CA Holley carb.
IMG_0693.JPG
 
Thank you! I'm looking at systems that are return and returnless. What I'm reading is the return line should pump back into the tank below the fuel level as opposed to spraying in from the top through the sender to prevent aeration. Can the vent tubes on the side of the tank be used as a return line inlet? I'm not sure if there are baffles etc. in the tank where the vent tubes go.
 
I strongly suggest a return type if you can do it, it will keep your fuel cool. I have this type in my car now, and it has worked great. I purchased two Hemi fuel lines for my car and routed them together. One is the supply and the other is the return. I also bought a custom gas tank with an in tank fuel pump.

Details are on my restoration thread if you would like to check it out.
https://www.forbbodiesonly.com/moparforum/threads/hawk-rod-the-restoration.65096/

Hawk
 
Thank you! I'm looking at systems that are return and returnless. What I'm reading is the return line should pump back into the tank below the fuel level as opposed to spraying in from the top through the sender to prevent aeration. Can the vent tubes on the side of the tank be used as a return line inlet? I'm not sure if there are baffles etc. in the tank where the vent tubes go.

I have the same question. Not sure if they are baffled...
 
Here is the inside of a California 1970 Road Runner tank. Note each of the four vent lines go to a corner of the tank. The "box" in the middle is used to effectively lower the overall capacity of the tank. IIRC, fuel then slowly bleeds into the box, which lowers the fuel level and avoids fuel spills due to a really full tank. There are no baffles.

Hope this helps,

Hawk

IMG_2455.JPG
 
Here is the inside of a California 1970 Road Runner tank. Note each of the four vent lines go to a corner of the tank. The "box" in the middle is used to effectively lower the overall capacity of the tank. IIRC, fuel then slowly bleeds into the box, which lowers the fuel level and avoids fuel spills due to a really full tank. There are no baffles.

Hope this helps,

Hawk

View attachment 1120786
That's interesting, thank's, I imagine the box bleeds in and out slowly, never seen the guts of a California tank before.
 
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