The OEM tank vent was never and will never be capable of properly venting the tank upon filling. The OEM tank valve was meant to handle expansion and contraction of the fuel due to temperature.

The only proper way is to fix the venting in the fuel filler. Look at the size of the fuel going in and how much the OEM vent can handle. Here is some information about a possible fix, although there are other ways.

Build Articles - Building - Custom Fuel Filler Pipe - myCoupe

 

You are the only other person on this forum who understands that the vent does not have anything to do with filling the tank. As you said all venting when filling takes place at the fill tube. Some how people just dont grasp the common sense that fuel going into the tank through a 3/4" fuel nozzle, under pressure, far exceeds anything that could exit the vent fitting. Fix the fuel inlet tube and you wont have any trouble filling your tank!

 

If you take a close look at the OEM filler piping, you will notice that it reduces in diameter at the tank end, and ends in a plastic check valve. I am certain that fill flow is substantially restricted by this reduced line size and particularly by the check valve. The 3.1 kit included a full size fill pipe and matching tank opening and seal. You still need to vent the top of the tank to a high point in the fill pipe to relieve the displaced air. But air should be expected to flow more freely than gasoline so I don't think the small vent line size is an issue.

DD

 

I installed one of these. Breeze Automotive Factory Five Racing

It came with easy to understand directions that you pull out the small white plastic one and use the same/existing rubber seal for this vavle.

 

Not needed

I have all the complete kit stuff and have no problem filling my tank.

Jeff

 

I am curious about this. With the pictures on the site Oxide linked to, cutting the steel outer tube and lengthening it with the 2" rubber hose per FFR shouldn't be any different than making a longer steel outer tube as the link said. They both create an outer tube carrying air around the inner rubber hose for venting. Shouldn't matter if it is rubber or steel. I would think that the bigger issue would be pulling the smaller fuel delivery hose back into the 2" steel filler neck because you lengthen the outside filler neck and not the inner fuel hose. That would have the gas splashing out of the inner filler hose inside of the outer steel filler neck and the venting air would be going through the splashing fuel, blowing it out of the vent. I don't see how the link solution changes anything as it just lengthens the outer filler neck with steel instead of rubber. It seems like the solution is to also lengthen the inner rubber fuel delivery hose the same amount as you lengthen the outer filler neck.