Thinking about all the liquid/vapor valves that I have had experience with in the past and have an idea which I just vetted through an friend who's an engineer in this very kind of stuff, and as long as you don't care about being factory accurate I have a viable inexpensive option for people who do not want to spend a bundle on or can not find an original LCV...
First off, LCV's are not magical devices. They don't even stop liquid from going through them at all, if they did we would not need a separate Roll-Over valve. If they fill up with gas under pressure it will go out the top. Basically what they do is they have two inlets going to different sides of the tank, the assumption being that at least one side will usually not be submerged. If gas is pushed up into it from the side that is submerged, it is an open chamber on that side allowing it to flow right back down into the line going to the side of the tank that is not submerged. Above this open chamber side of it is a media identical to what is in fuel filters, at least on the newer model my friend has taken apart though he admitted some old models may only have a series of baffles. What this media or baffles to is to "slow down" the fuel going through it. If it's under pressure such as from a fuel pump it wont slow it down much, if it's not under pressure such as just fuel from a tilted tank pushing up into it then it slows it down more. Even with a light vacuum such as from the canister it's not enough to pull it through much faster. Most of the trick to what they do is simply to add TIME, a delay, for the gas to fill the entire chambers both below and above the media until the entire thing is completely full of fuel and only then will it start to come out of the top. This delay time gives the vehicle time for the gas to drain back out of it. Remember even with a light vacuum from the canister vacuum will ALWAYS pull air/fumes/vapor FASTER than it will pull a liquid such as gas. So your Jeep is sideways on a hill with a fairly full tank; what happens is one sides vents are submerged trying to push fuel up into the LCV canister, while the other side is not submerged, the canister is trying to apply a light vacuum but it's going to pull the vapor through from the side that is not submerged, bubbling up through the gas inside of the LCV's canister and combined with the delay it takes to fill the entire canister this gives time for the Jeep to come back down on level or the fuel to drain back down the hoses, even through the lower part of the same hose that it's drawing vapor up through.
Now, think about this... What do we (especially Jeep owners) know that has a single hole on one side, two on the other side, and otherwise is basically canister with a filter media inside? Uh, yea... duh... Our fuel filters!
Our filters are not directional, there is no check valve inside of them, both fuel and vapor can pass through them in either direction. So two of the nipple sizes are wrong (though you can often spray some lubricant on a hose and work it up on the next larger size nipple) but other vehicles do use similar filters with one in and two outs and some small Japanese vehicles even have all of them in the same 1/4th inch size that we need for an LCV. Many also come complete with brackets around them to mount to a frame rail. All we need to do is to turn them up ended with the two outlets down and the single outlet up and connect them just like we would our stock LCV. Make the line as straight from the inlets to the tank vents as possible so fuel can run straight back down into the tank if it gets up into it (ie. no loops, this just traps fuel). Then come out of the top making an S and coming into the bottom of our Roll-Over valves, my engineer friend suggested mounting our roll-over check valves higher than the LCV and doesn't understand from an engineering standpoint based on how they work together why Jeep ever had the LCV mounted level with or lower than the roll-over valve. The final step is to come out of the top of the roll-over valve and go UP HIGH, loop the line upwards and back over the top of the roll-over valve and the filter and back down to connect to the hard line going forward to the canister. You now have a chamber to collect fuel pushed up during turns and allow it to drain back down quickly, a media any fuel must push through before it can go up any higher, and even if it does it still has to get all the way up to the roll-over valve, through that, and back up through the loop that goes up before coming back down again. For the price of an inexpensive fuel filter that you simply turn vertically on end instead of keeping horizontal you have simulated the basic functions of how an LCV works. My friend did point out that if doing this to choose a fuel filter with as much or more internal volume as the original LCV had, which should be fairly easy, just don't choose one of those little tiny filters.
As I said, I checked this idea with an engineer friend of mine who says it should work great for those not willing to pay for or who can not find a specifically designed LCV, and is certainly a whole lot better than nothing at all! However, like most home remedy's with these Jeeps, choose to use the information at your own risk.
~ SouthernGypsy's Jeeps ~
2004 Jeep TJ Rubicon 4.0L/Automatic
1983 Jeep CJ-7 Limited 4.2L/5 Speed