In my evergoing search to learn things that might help some of ya'll out, and also 'cause I like to rip stuff apart,:) here are some pics of my old gas tank after I cut the top out of it. 1st pic is of the vent tubes as they come out of the tank. 2nd pic is of a 6" x 6" section I cut out above the tubes. Notice how the small tube runs off at an angle to the left rear of the tank, and the big tube just stubs out about 1" into the tank. 3rd pic is when I cut the whole top off of the tank. Now you can see where the little tube goes. 4th pic is a close-up of the large tube. Notice that it's crimped almost shut, but there's still enough of it open to allow air to come in (and fuel out). Also note the orientation of the "U" on the tube--it's in a position to hold the fuel in a small trough, which I believe is the reason that it can leak (this can also be seen in pic 2). If the "U" was turned upside down, fuel couldn't stay in it & that would keep it from leaking outside of the car. That's my story, & I'm sticking to it. I think this is also true for the 69 gas tanks, but one of you will have to chop open one.

Also notice that the tank is clean & rust free. That means that I just destroyed a perfectly good piece in the name of Chevelle science!:clonk:
Hope this clears up some questions for ya.:thumbsup:

BillL

BTW, if anybody has anything they want destroyed, just send it over!!:D

I think your gas tank has a bigger leak now than it did before

that is pretty neat though

did you fill it full of water before you cut it up?

just wondering how you did it without sending yourself into orbit :D

Bill won't be awake to reply before at least nine, central time. :D

Danny,
Now we know how he spent the money :D

Well at least now i know what it looks like inside:). Still don't know how to get it to stop leaking. I've tried everything, they had to leak from the factory didn't they?

Interesting !

I think your gas tank has a bigger leak now than it did before

that is pretty neat though

did you fill it full of water before you cut it up?

just wondering how you did it without sending yourself into orbit :D

Drained the gas out (got about $8.00 worth) filled it with water, took out the air chisel & cut 'er open! :)

Danny & Bob, it was either get a new tank or try to figure out how to take the undercoating off of the old one. Plus, I figured after 37 years the inside would be pretty cruddy. Guess I was wrong on that one. BTW, it's 10:15 now :p

BillL

Bill,

So can you explain why I spent $40 on that little plastic vent that hooks to those tubes?

Oh by the way, when I got back from CB05, I fixed the gas guage. Know what the problem was? There was no gas tank vent, they were plugged. And the tank sucked itself into itself! :clonk: not sure how i made the 550 miles home....

So, does anyone really know why these leak. My 69 leaks when full or when partially full and it is warm outside. I have replaced the external plastic tank vent and put in the required foam, but it still leaks.

Would blowing compressed air into the tank via the vent tubes make any difference? Any opinions? Could an obstruction inside cause the venting?

I bought a new tank, but the old is in great shape with the exception of the venting.

By the way, thanks for sharing the cut-a-way of the 68 tank. That is dedication to this hobby.

Woj

The way the tanks are made, the only way to prevent it from leaking is to keep the tank less than 1/2 full, park on a level surface, and never hit the brakes hard enough to let the gas slosh into the vent tube. :clonk: Or figure out a way to extend the vent hoses to a length where the gas won't be able to get out. Or find some type of check valve that's impervious to gasoline & will allow air into the tank but not allow liquid to come out. I'm working on it, & when I find a solution I'll let everyone know. :)

BillL

I went through lots of trial and error with my 69 when it was puking gas with the stock vent setup. I finally took the whole thing off and replaced it with a metal fuel filter (2 hose nipples on one end and a single one on the other) and ran rubber fuel line across the top of the tank and zip tied it to the filler neck. It seems to work and now if it pukes it will be at the back of the car and not around my exhaust system. The tank seems to vent and I have not noticed any fuel leaking.

Or find some type of check valve that's impervious to gasoline & will allow air into the tank but not allow liquid to come out. I'm working on it, & when I find a solution I'll let everyone know. :)

BillL

I have the vent stubs capped off on my 69 and the tank builds up positive pressure when driven several miles.
When I stop to fill up and loosen the cap, the pressure almost blows the cap out of my hand.

When I first capped them off I put on a vented cap but had to put the unvented cap back on because gasoline always dumped out through the vented cap every time I took off fast.
It never drips any gas this way though.

Mine doesn't leak. Not sure why. I have a new tank and sender. I used the original non-vented gas cap and the original vent. My vent is as high as I could get it, up in the bracket that holds it. My 68 is only driven short distances at shows, but I'm sure the gas sloshes around plenty in the trailer. I'm wondering if the material inside the vent deteriorates over time and allows the gas to leak back thru the larger side.

I drove my 69 for 4,000 miles and never leaked a drop. Same setup as 71SSBB, except I put a piece of lawnmower air filter in the vent.

I too have a new tank, sender, straps, etc.etc....I have two pieces of hose that go way up in the straps attached to the body and have not had any problems....I think the level of the hoses HAS to be above the level of the outlet by a fair amount in order for sloshing to keep gas from going up there.......

While I'm still the king of posts on this, you just saved me a ton of time! I was going to do this in about 4 weeks. I'm SO sick of this thing. Everytime I think I've got it fixed, it does it again.

Here's the history : Gas Vent thread in Troubleshooting Forum (http://www.chevelles.com/forums/showthread.php?t=26088)

Thanks for the pics! Now, how the heck am I going to move forward with this? I've extended my lines before and it didn't work.