I've posted before on this, and I know others have as well, but this issue is reaching critical mass.

My '68 Chevelle spews gas violently from both vent lines. I'll hit the high points of what's been tried/done.

New stock 1968 gas tank with two vent tubes. No restrictor since those are no longer available. New rubber lines to the hard line on the supply side, both new vent lines cut to the size as original. New NON-vented gas cap as from the factory.

When the tank has any gas more than 1/4 tank (according to gauge) it will vent a nice puddle of gas out both vent lines. This is obviously a dangerous and smelly situation. I've even tried a vented cap, but to no avail.

I belive that this problem stems from living at 7000 feet in altitude and that they sell us crappy gas that has a higher than normal alcohol content. Therefore on a hot or warm day, the gas expands, pushing itself out of the vent tubes.

I believe the '70 and up cars had vent tubes, vented caps, and a canister in the engine compartment. I am interested in putting a canister in, capping the smaller vent line, running the 3/8" line to the cannister.

Any problems with this? I have few concerns, like the gas managing to push all the way to the canister. The only upside I can think of is that the cannister would be higher than the gas tank and might help only vapor escape.

Any other thoughts?


Thanks in advance.

I don't know if this helps. My buddy had a similar problem with a mustang. His exhaust pipes ended directly in front of the gas tank. On hot days sitting in traffic, he would start spraying gas out of the overflow. This is in south Louisiana however. Dont know about your exhaust, but something to think about.

Hi,
I have a 69 with the same problems you have. I even have have the original plastic surge vent you speak of. I was doing some work recently and I was shocked to see the fuel spillage down the tank and on the exhaust pipes. The car was originally a 6cyl./powerglide combo. When I restified it I set it up with a big block/4 speed and dual line set up as opposed to the single line set up with the 6cyl. All set up was done as close to "correct" as possible. Do you have a single or double(return) line set up in your car?
I read an article in an NCOA magazine addressing this issue (several years ago) but, I no longer have the magazine. Maybe some member still has theirs and could help us.
Thanks and Good Luck,
Steve

I have a similar problem with my 68 Elkie. I get a terrible gas smell in the car whenever I make a hard turn, like a 270 degree freeway ramp. I was about to buy a new tank, but see that didn't solve your problem.

I can't see what's on top of my tank - do I need to drop it to see if I even have any vent lines connected? I seem to remember an old Oldsmobile I used to have had a 'charcoal' canister mounted in the rear wheel well that the tank vented to. Would one of these help?

I plugged up those vents.

Then to let air in & out of the gas tank, I drilled a TINY hole in my gas cap. It's not perfect, but better than a gallon of gas dripping on my exhaust when I park.

I have an un-drilled cap that I use when I go to the track, then remove it between races long enough to equalize pressure (about a second).

-Bob Cunningham

I also capped off those vent tubes and put on a vented cap.No problems yet.

David

I've tried everything throught the years to stop this problem. What I'm doing now has worked for about 3 years now. I plugged one of the vents and ran a rubber hose made for gas from the other one across the front of the tank up high to the other side of the car, down the side of the tank to the back of the car and over to the center of the tank and put it through a hole all ready in the frame. If I have a full tank on a hot day it might drip a little but its better than dripping on the hot exhaust. Hope this helps.
Harold

Dave:
Hi from another Colorado Chevelle owner!
I’ve had several 69’s, and just dealt with the dripping gas, but the engineer that designed it to drip directly on the hot exhaust system should be shot. On my current Chevelle I also added Fuel Injection, which greatly exacerbates the problem. Fuel is pumped from the tank to the engine, picks up heat from the engine, and the hot fuel returns to the tank. The fuel in the tank then expands and the vapor vents out thru the vent tubes. When you turn left the vent tubes are under the fuel level, and the vapor pressure pushes fuel out thru the tubes, but even without that there is a lot of exiting vapor, like sitting in the garage after driving around. My garage smells like a refinery- I’m glad I don’t smoke or I might not have a house by now. I tried plugging the tubes and using a drilled gas cap, but the tank swelled and it sounded like a teakettle. Long story short- I think I may have a solution; I’ll run it by you guys. I know I haven’t come up with anything new, the 70’s Chevelles have this system on it, but nobody makes a modification kit for 68-69’s, so that is what I did. The trick seems to be to have a vapor separator with enough capacity to hold the fuel that spills when cornering or braking, and return it to the tank, while capturing the vapor so it doesn’t vent to atmosphere. I build a sealed ½ gallon canister with three tubes that mounts above the tank. Two of the tubes attach to the gas tank vent tubes: One for the fuel vapor (connected 2/3 from the bottom), and one for the returning fuel (connected to the bottom). The third tube vents the top of the canister, and runs to a charcoal canister in the engine compartment, which in turn connects to engine vacuum. It’s been installed a couple weeks now, no more spilled gas, but my garage still stinks (not as bad though). I think it may just take a while to air it out. Is it just me, or does gas smell worse than it used to? I don't remember ever being offended by gas fumes in the 70's, and cars just vented gas to the atmosphere. Now my eyes burn, and I can't stand the smell. Old Age? I'll stop rambling now.

Wilbur

Gents,

Thanks for the replies. I've currently got a vented cap on and plugged the 3/8" vent, but it spews heavily out of the smaller one. I suppose it is possible that the spring in the vented cap doesn't get quite enough pressure to release, so I'll plug the smaller vent line as a test.

Harrold, haven't talked to you in a while, glad to see you're still around! Sounds like a possible solution with your method too. You've added probably 5 feet of hose to the system, and maybe that is one of the keys: getting enough line in to allow the vapor, but not gas to get out. Kinda what I was thinking with the line going to the front of a car and running into a tank.

Hmm. Of course it's suddenly going from 84 yesterday to 50 today, so this might not get a good test this weekend.

I'll let you know what I find.

Originally posted by dreinecke:
I've currently got a vented capWhere did you find a vented cap? I tried DOZENS of vented caps and none of them fit. My conclusion was that GM intentionally made them not fit, so you could not swap them accidentally.

A part number or application would be REALLY appreciated!

-Bob Cunningham

Bob,

It's a Stant locking cap. I don't have the car here at the house right now to check the # though...I'll try to get it this week for you.

Hi to all,
I'd like to keep this one going. I have the same problem with the gas spilling down on the pipes from the vent. We've had the car since 1975,
in 1988 I started a frame-off resto, originally the car had a 6 cyl./powerglide combo with single gas line set up. When I restified it, I installed a 396/4 speed combo with dual gas line (return) set up. The tank is original, I even have the plastic surge fitting but it is missing the restrictor as listed in the assembly manual for 1969. I have a couple of questions for discussion. Does anyone know what exactly the restrictor is? Secondly is the tank venting setup the same one the six cyl. single line vs, the eight cyl. with the double line. Thirdly what is actually happening when the fuel spills? is it slosh, expansion, or what? I am using a non-vented cap (correct?) so I believe you need a vent to allow for pressure equalization. Can anyone help on this potentially dangerous situation. There seems to several of us with this condition.
Thanks in advance,
Steve
69 post (2dr sedan) :confused:
2nd owners since 1975

I also have a 69...car did not have the plastic surge/vent...as many do not, just the two hoses clamped to trunk floor. Found some cars with a foam material in both hoses. Strange how some cars had this part, others did not. But anyway, I found the plastic surge/vent, installed it, and at the top pipe I installed a piece of lawnmower foam. This allows venting and also absorbs any fuel that does not return to tank right away. I know the restrictor you speak of is made of foam, as a friend of mine years ago did a parts locator and found one...he was surprised to see it was foam...in a GM package..it is approximatley 1/2" long X 3/8" Dia. I have this all installed as per the assembly manual, graemlins/thumbsup.gif and have not had any fuel surge problems, or venting. My car is a 69SS

Hi,
Believe it or not that's EXACTLY what I did!!!
Do you have a non-vented cap and two line system?
I don't think I had the problem before I changed from the single line system.
Thanks for your input!
Steve

I did the same as black&red and no problems here either,two line system with non vented cap.Just saw one of those vents for sale somewhere? This site or E-Bay. Mike

I have the 2 line system...that was used on Q-Jet equiped engines, 325, 350 Hp, 375 hp. Holley engines had a single 3/8" fuel line and no return line...single system. Find one of those surge restrictors, install as shown in the assembly manual, put some of that foam in the top pipe, and you should be fine. When mine had just the 2 hoses off the tank..original..I would get some gas come up and run down the tank...too dangerous for me as my tailpipes are 2-1/2" stainless and close to the tank...sure didn't want an explosion. Strange thing is why some of these cars got hoses and some got the surge/vent????? I have also been told you can find these vents on other GM "A" bodies...GTO/LeMans, Cutlass, Buick Skylark. Hope this helps.... smile.gif

Oh...forgot, NON vented cap as per original... graemlins/clonk.gif

Hey Guys,
I must be doing something wrong. I have the two line system as per original, surge vent as orig., non-vented cap gasoline resistant (air filter foam) stuffed in the end. even the original bracket to hold the surge vent in place. The gas washed all the undercoating and paint off pan and onto the exhaust pipe and underside of the fuel tank.
Steve :confused:

Since I didn't have the part, I plugged the vent lines and use the original non vented cap.
I tried a vented cap at first but it always dumped gas out when I took off a little fast so I put the non vented one back on.

It's been that way since 1986 and I haven't had any problems except when I drive long distances on the highway, the tank becomes pressurized and blows out a big whoosh of air when I remove the cap.

Anyone have problems with their 69 smelling like gas? I am addressing the same issues you all are with the tank venting, right now I have the larger tube from the tank plugged, and the smaller one unplugged and in the clamp so it's facing upward. Non-vented cap.

I don't have any problem with fuel overflowing out of the unplugged tube up to about 3/4 of a tank. However, even though no fuel is spilling out, it smells extremely strong and stinks up the whole garage. I have no fuel leaks that I can find. Is it possible that just venting the tank through that smaller hose could smell that strong???

Anyways, still looking for that original plastic overflow thingy with the foam...

Dave,i have 69 that spewed fuel onto hot pipes out of the gas tank vent,it started to smoke and i flipped out,but luckly it never ignited.

Just like Bob C stated above,i too just plugged those 2 vent lines off and drilled a small hole into the fuel cap to allow some air into the tank and have not had a problems for the 26 yrs i have owned the car.

I still hook up a non functional vent hose to the fuel pump to retain the stock appearance.

Scott

Pardon my ignorance about this topic, but I'm getting worried about fire, explosions, etc. I would hate to see my 70 El Camino, original 396-350 hp, go up in flames.

It has two lines coming off the tank, one of which is a return line. The tank and lines are original as far as I can tell. Both lines run to the front of the car. As far as I know, the tank has no vent other than whatever might vent through the gas cap.

Where would the overflow or leakage come from? Out the fill pipe? or out of the connections where the pipes from the tank join those running to the front of the car? What should we look out for?

Thanks.
David

If you are laying under car feet out the back,there are 2 hoses with a little plastic vent in the upper left hand corner. Mike

I followed Harrold's idea of routing the vent tube around the tank. I did add a fuel filter in just for the heck of it.

I'll post back how it works.

Thanks for the tips.

Dang! Doing Harrold's trick still didn't solve the problem. I ran both lines into a fuel filter with dual inlets (3/8" and 1/4") and a single 3/8" outlet. I ran the vent line from there across the front of the tank, up high. Then it runs down the driver's side frame rail next to the gas tank, halfway across the back until just below the filler neck, it turns out of a pre-made hole in the frame. Full tank and even half a tank makes it puke. Not as bad as before, but a nice puddle nonetheless. And that was on a 40 degree day after a 15 minute drive up the highway.

I guess I'll try drilling a pinhole in the gas cap. At this point I don't know what else to do!

Even that isn't the perfect solution! But your spillage will be reduced to a very light splash instead of significant puddles.

-Bob C.

I have a 70 El Camino SS 396 with the 1/4" return fuel line. I also have the same problem where if you make a hard right turn, the gas sloshes out and runs down the fill tube for the gas tank and onto the left exhaust pipe. Also, if the vehicle sits for a period of time in warm weather, the tank seems to have the gas expand and spew gas out the fill tank if the tank is fairly full. I replaced the gas cap with a NOS vented gas cap and still does the same thing. Is this something I will have to live with or is there a fix for it?

Ok, an update. I'm still running 5 extra feet of line in the system. I've used a PCV valve to cap the line. It still would vent liquid out. I've now plugged the line completely. I change about 400 feet in elevation driving home. The tank "pops" non-stop. Scared the crap out of me, because I hadn't heard it before. It obviously freaked the sending unit out, because I went from 1/2 tank to empty in no time. Taking off the cap almost removed my hand. As soon as it vented, the gas guage returned to 1/2 tank.

I'm ready to try a vapor seperator and a vapor cannister.

Any other suggestions?