Gas Tank Modifying and Sealing - These Fuelish Things

9 With the base of the filler neck, and some lead, removed...

10 ... I chose to enlarge the hole outside the damaged area and weld in a square patch with rounded corners.

11 With the repair patch trimmed and bent to the same curvature as the tank, it was tacked in place then seam-welded in short sections, as the tank was extremely thin and blew through in a couple of places.

12 The hole left from the stock drain plug was also welded closed. Compressed air was used to cool the weld between stitches and keep warpage to a minimum.

13 Kirk Brown at Crafty-B supplied this super-cool, vintage-style flip-up gas cap, which uses a mix of cast and polished aluminum as well as brass, for contrast and appearance. After measuring and marking the central point on what was now the top of the tank, I laid some masking tape down and pressed the cap and base, with its mounting bolts inserted, into the tape to mark their locations.

14 The mounting holes were drilled (note how the new cap overlaps the old drain plug location but doesn't completely cover it) and the filler hole drilled then opened with a rotary grinder to match the size of the hole on the cap base. It was here that I noticed the central baffle inside the tank, which explained the offset drain plug!

15 The Crafty-B caps are normally supplied with a flat base, but I asked Brown to radius mine, as I knew it'd be going on this tank. He got it pretty close with just a phone description to go on, as you can see, and I only had to do some minimal grinding on the base to totally match the curve.

16 I bent up a short section of 3/8-inch stainless steel tube and welded it on one end of the tank, drilling 3/8-inch holes in the tank first. I'll remove the middle part of what looks like a handle, and with a length of clear tubing in place, it'll serve as a gas sight gauge, eliminating the need for a fuel gauge sender and associated wiring on a tank that will be mounted totally on view. Fabricating it as one piece meant the ends would align later.

17 With the tank modifications complete, I wanted to pressure test it for leaks, so I made a cork gasket for the filler cap, using a punch to form the mounting bolt holes as shown. You'll also note I "massaged' the baffle over to one side to allow the tank to be filled.

18 To access the nuts on the mounting bolts I modified a short 3/8-inch wrench to suit. Well, that sounds better than saying "I clamped it in the vise and whacked it with a big hammer" right?

19 The stock sending unit incorporating the fuel outlet turned out to be fortuitous as I was able to put it back in and use a blower on my air line through the old outlet to pressurize the tank. Soapy water is best to show leaks (remember fixing flats on your bicycle as a kid?) and a spray bottle of auto glass cleaner is ideal.

20 It transpired there were two pinholes around this patch, as can be seen from the bubbles (arrows), though the end of the tank where the sight gauge was fitted contained several, mostly around the seam where the end plate was welded to the tank. Incidentally, it didn't take much pressure before the ends of the tank started to "balloon".