My filler neck modification

[cmayna]

OK, don't know where to start on this subject but ever since I installed a '69 (20 gallon) tank in Shag, I've had nothing but headaches. Due to the location of the snout on the tank no normal 67/68 neck would fit, nor would a 69 neck on a 68 car. Thus I had a 67/68 neck chopped and shortened. It never worked without back splash and premature shutoff.

67/68 necks have a very right angle bend. So when we Californians insert the pump's nozzle we are basically shooting to the back of the throat which causes the gas to splash right back resulting in either gas splashing out at you or premature shutoff. We are not shooting down the throat.

While I had the 20 gallon ('69) tank still in Shag I got one of Tarafied1 modified neck. Since the snout of the tank was in the wrong location I had to modify the neck even more resulting in more of a right angle bend, causing that much more backsplash and vomiting of the tank.

I removed the 20 gallon tank and installed a stock 67/68 16 gallon tank but before I installed the new tank I opt to solder in a bung vent connector on top of the tank based upon a post I read in another forum which talked about with the amount of gas that today's pump delivers in our tanks there wasn't sufficient means of the air in the tank to escape. So this vent was a good means of the air to escape up to the top of the filler neck. That is only part of the solution.

So, based upon the idea that the 67/68 neck has a bad design of a right angled neck which causes you to shoot the gas to the back of the throat resulting some of it back splashing back at you, I decided to modify a 65/66 neck which is much straighter. I chopped and modified a 65/66 neck to fit the 67/68 dimensions, which allowed me to stick the pump's nozzle inward and downward forcing the flow of the gas to go straight down the filler neck.

I have been able to fill the tank at full blast two times in a row. Each time I could hear the sound of the gas coming up to the top but more importantly I was able to see the gas starting to splash up into the vent tube and then fill it completely to the point that once I have filled the tank the level started rising up into the clear vent tube telling me the filler neck started filling up. Thus I for sure knew when to stop.

The three pics below are as follows:

A non modifed 67/68 filler neck installed with a black fuel hose vent system and a 16 gallon tank:

A 65/66 neck modifed and tapped for a vent.

Same 65/66 neck installed with a clear vent tube for ease of watching the fuel start to come up.

This setup will NOT work for most because:

1. You cannot solder a vent bung without emptying the tank, removing it and having it flushed out first. I happen to have a new tank to work with.

2. Due to the sharp angle of the filler neck's tube, the taillight panel center brace (internal trunk piece that the filler neck goes through has to have it's vertically ovalized opening cut further down towards the tank. I had this done way back when Shag was having it's body makeover.

Long term I will not keep the clear vinyl vent line for gasoline causes vinyl to harden and eventually will be brittle. This is for now only a educational step.

I can pretty easily say that I feel pretty comfortable in being able to fill the tank at full pressure without any backsplash as long as I point the pump's nozzle radically downward into the throat of the neck from a 6 o'clock position. This upcoming weekend's trip to knotts which will require at least 6 fill ups will reveal if I resolved the issue or am I full of hot air.

 

[tarafied1]

interesting, but I'm surprised you have had trouble with splashback. The mod I make pretty much eliminates any opening for fuel to come back out which should cause the gas station nozzle to shut off. I do agree the 67/68 and even 69/70 have a pretty sharp angle.

 

[gtscode]

Can't wait to see how it goes for you!

 

[cmayna]

interesting, but I'm surprised you have had trouble with splashback. The mod I make pretty much eliminates any opening for fuel to come back out which should cause the gas station nozzle to shut off. I do agree the 67/68 and even 69/70 have a pretty sharp angle.

Craig, As I had previously mentioned with the neck you modified for me was that I had to modify angle of the tube to fit the 20 gallon neck. I had to increase the angle which increased the problem of the nozzle point at the back of the throat of the neck instead of down the throat. Yes even with your modifications the gas was spilling right out at me. It's not a perfect seal otherwise air from the tank couldn't escape.

As we see in most modern cars the pump nozzle is typically pointing down the throat. Even my 50 Chevy truck has a straight neck so I have never had this type of problem. Thus my goal was to modify a neck so the nozzle point down the throat as parallel as possible while holding the pump's nozzle at a 6 o'clock position.

But as most of us have seen, not all gas stations have the same exact nozzle, so who knows if I will still encounter fill up issues.

 

[KBMWRS]

Yes Craig likes it straight down the throat...no hitting of the back of the throat causes that reflex....backsplash. :roll

 

[tarafied1]

I understand the problem, I was just wondering why the nozzle didn't shut off when the fuel hit the back of the neck. My understanding the nozzle design is that it senses pressure build-up or fuel coming back and shuts off. The vent idea sounds good. I got a fuel filler modified by someone else that has yet another concept. I'm going to put it in my car and see how it works.