[ByronRACE]

I'd volunteer to help, but this is a fuel tank...and you want a very good, very experienced welder. I did a lot of the welding on my car, and have a little 185A tig machine in the garage...but when it comes to something this important, I would advise you to go with a pro. In fact, when I build my tank, I'm going to employ the services of a pro. One pinhole and you get to do the prep work all over again; it's just not worth it.

And...make sure you soak the insides of that tank with a good detergent (dawn works well) and water...but not too long; you don't want corrosion. Overnight is ok. Don't use any cleaner that has an acid base (vinegar is bad) and don't use something caustic (like automatic dishwashing detergent, also bad) or it'll eat the metal. I'm sure the welder has tricks to insure he won't explode. If he doesn't, I recommend a shop vac or electric leaf blower hooked up to the tank to keep the air exchanged. This is also a convenient way to dry it. It's very hard to get a proper air/fuel ratio for an explosion with that much air circulating. I prefer vacuum; the pressure method tends to make it harder to weld.

Lastly, pressure test it. Just extend a tube vertically off the filler neck about 2ft, cork up the tank, put it up on blocks so you can see and touch all the weld lines, and fill it with water. Head pressure is about 2.3psi per foot above datum. 2-3 ft is fine. Don't go too crazy, there's a lot of surface area there, and force on the wall is multiplied by every square inch...I'm sure you know this. That said, I saw a guy do this with an 8ft pipe because that's what he got from home depot...and more pressure is better right? Wrong, he broke his tank. 18.4psi, 33x15 tank top. Lots of sq inches; lots of force.

Byron