A shop that knows what they are doing - might use processes and procedures to limit the possibility of the tank exploding in their face. Gasoline vapors remaining in old gas tanks are very volatile and if ignited can produce very powerful explosions.

FWIW,

Carl B.

Thanks for preventing me from doing something stupid and foolish, as I was planing on welding the tank while it was full of gas vapors.

Edited February 20, 201114 yr by grantf

A friend of mine welded the tank I got for the 620. His procedure was to fill it up with water, then after draining and refilling he would set a match to it. But I wouldn't do it if you haven't done it before.

Then you can look it up on the web and read a lot of different ways, one is using exhaust from a running car, but then you would want to make sure that car isn't running overly rich.

So best thing to do is let a professional handle it.

If you drain the tank THOROUGHLY, blot up any remaining pool of gas with a paper towel taped to the end of a stick, and let the tank bake in the sun with the filler neck pointed down and the sending unit removed, the gas will be gone before you know it. (Might have to wait for warmer weather, though.) Use your nose. And as always: Try this at your own risk. I'm an idiot, and you shouldn't be taking my advice. So you're warned!

@Venus (Karen): An RX-7 in the attic?! I'm impressed and humbled!

When my local metal guy welded my custom tank, He mentioned something about filling the tank with an "Inert Gas". Something about it also helping suck the weld inside as well. I tried to upload the shots, which are all the same size etc, etc, but it will only let me upload 1 pic?? I'll try and show the inner shot later on, after I restart my computer.

Can't upload the close-up pic but this inside shot shows how the weld was sucked in by the inert gas. So it looks like he welded the inside as well.

Edited February 20, 201114 yr by Zs-ondabrain

Thanks for preventing me from doing something stupid and foolish, as I was planing on welding the tank while it was full of gas vapors.

Hi grantf:

I seriously doubt that you were.

You never know who is lurking on the site, that might take everything at face value and proceed without thinking every aspect of an operation though. I'll be 66 this year and I've lost track of the number of times I've done something really stupid, when I actually knew full well that it should NOT be done and for what reasons. I just didn't think about it at the time.

FWIW,

Carl B.

Hi Dave:

Great pictures and very nice welding on thin metal. Your local metal guy would seem to know what he is doing.

Your tank looks nice and clean inside -

We all know that water and gasoline don't mix.. so rinsing a tank out with water seldom removes all the old gasoline trapped in the varnish, crud, corrosion and rust in an old gas tank. Most professional shops, use chemical rinses mixed specifically to remove them, so they don't act as a sponge for gasoline and its vapors. You can rinse a gas tank out ten times with water and the old gas varnish will still be there.

Filling the tank after its cleaned, with an inert gas is a good procedure as well. That would reduce the chance of flash rust forming on the welded area's - before you could treat them, or refill the tank with gasoline.

FWIW,

Carl B.

Here is good one from the 40's

Thanks for the tip Dave, I was actually going to ask you about that tank. I saw pictures of you're modified tank awhile ago. The tank looks really clean on the inside, that's why I bought it so I think needs no cleaning. It is "bone" dry right now, I have put my nose to it and I smell no gas at all. It will sit in my basement for some time before I start any work on it as there is other work to do for the time being. The hole is about 1 inch in dia. so if I decide to weld it I wonder if I could just use the same mig gas I use with my wire feed (Metal Inert Gas) to fill the tank.

here is a shot of the tank (not easy to photograph the inside sorry).

This is the drilled out hole and a little rust, this is the only rust in the tank I believe is is caused by water entering through said hole.

that's not too bad at all. Hell, you could rubber plug that hole, in a pinch. OR... Square off the hole, weld in a filler plate, spray or brush on a protectant from the inside (you'll likely have to use a stick or extension to reach the hole repair on the inside) then POR15 the outside? just a thought.

Oh and the center console.....

needs some cleaning but wow for 16 bucks no one grabbed it?

Edited February 22, 201114 yr by grantf