The following is presented for informational purposes only. Actually performing this mod to a "post ban" fuel can probably violates some BS federal law. Also, if you ignore the preceding, ONLY do this to a NEW can that has NEVER had fuel inside. I don't want to hear about anybody blowing themselves up, and I especially don't want to learn about it from their grieving widow's attorney. As always, if you decide to do something stupid based on something you read on the internet, you are on your own!
So with that out of the way, unless you have been living under a rock for the last year and a half, you should be aware that the EPA has banned the sale of "good" fuel cans as of January 1, 2009, and has essentially adopted California's "CARB" standard for fuel cans on a nationwide basis. What this means in a nutshell, is that unless you manage to get the "preban" style of jerry cans, you will be stuck with something that doesn't pour worth a damn, and probably doesn't seal very well, either.
Now, I bought several of the superior NATO style cans before the ban went into effect, so I didn't really need to do this, but I happened to end up with one of the "post ban" metal cans manufactured by Blitz as part of my bumper fabrication project, because I wanted to make sure that my fuel carriers would hold both major styles of metal cans. With that project finished, what to do with the Blitz can? I could leave it out at my remote property for storage of emergency fuel, but I don't want to be dealing with a can that won't pour right if it actually is an emergency, so that's out. Luckily, it is possible to restore the newer cans to more or less the original design configuration.
First, the good news. The "post ban" style cans will still accept the original flexible metal spouts. This is a huge deal, because it makes restoring adequate pouring action possible. The bad news is that they totally eliminated the vent tube from the can, which means if you simply plug in the flex nozzle and expect it to pour properly, you are going to be sorely disappointed. To use the old nozzles with the new cans, you need to restore the design's original venting properties.
The first thing I did was go to NAPA and buy a length of 3/16" steel brake tubing. This tubing has an inside diameter of just over 1/8 of an inch, which is reasonably close to the original tube size, and should provide adequate venting. The way these cans originally worked, is the pouring nozzle and its gasket are not a large enough diameter to cover the tube, so when pouring, air can flow into the can to replace the volume of the fuel that is pouring out, leading to smooth pouring of fuel. The cap and its gasket, on the other hand, are of a larger diameter, such that the hole is covered when the can is sealed, so that fuel cannot spill out of the vent hole. Therefore, the placement of the vent pipe on the mounting flange is fairly crucial.
In this picture, you should be able to see the different sizes of the cap and pour spout flanges, and the lack of a vent hole/tube in the can's flange. Also note that the new cans come with an O-ring seal instead of the original flat gasket, so a new gasket will have to be made or acquired.
Scribing a line to mark the position of the edge of the pouring spout flange. From there, based on the size of the tube you are using, you can determine the center of the hole to be drilled, such that the edge of the hole is tangent to the edge of the pouring gasket/flange. I drilled a 3/16" hole initially, but had to open it up to a #11 hole to get my tubing to fit.
The tube that I used. You'll need to cut off the flares and remove the nuts, of course.
The tube bent and trimmed to fit. I used a tubing bender to avoid kinking the tube, but you may be able to get away with bending it free hand. Be sure to deburr the ends, inside and out. You don't want anything obstructing the flow of air inside the tube. The end of the tube needs to be positioned so it ends in the air pocket in the upper rear of the can.
The tube positioned, with some of the surrounding paint removed to avoid contaminating the joint.
The tube brazed in place. Silver solder probably would have worked as well (maybe better), but I used what I had. After it cools, cut off the tube, and then file flush. Be sure to put some duct tape over the mouth of the can, to prevent debris from falling inside. I also did that when drilling the hole. It's probably a good idea to slosh a little fuel around in there and then empty it out to help eliminate any stray bits of metal that might have fallen in. Also be sure the vent tube is deburred internally again once the tube is flush.
The finished can, with the tube smoothed down and rattle can paint applied. I haven't tested this yet (I still need to make a gasket for the cap), but it should work just as well as a pre-ban Blitz can. At this point it is still easier to find the older ones, but like I said, I ended up buying one to use as a fabrication dummy, so I had it around to experiment on.