Gas Tank Filler Necks: Anatomy/Physiology?

[Lynn]

I had a tank with a small hole punched in the bottom once, and soldered a penny on to the hole.
That's the short version.

The long version cost me some eyebrows. Seems the metal actually absorbs a bit of petrol over the years. I completely emptied the tank. Let it sit for a day. Ran a garden hose in it until it overflowed for about 5 min. Emptied the water. Let it set til the afternoon. Set the tank up on a work bench, cleaned the spot really well, went to solder the penny on, and as soon as I hit the hole with an open flame.... BOOM. Of course, I was standing right over the hole for the sending unit.

Fortunately, it only slightly balloned the tank.