Tanked Up

With the ever increasing price of petrol and rapidly decreasing number of service stations it has really become essential to be able to buy-up-big when you see cheap fuel. Fitting a XR - XY tank to your Early Falcon can save you time and money. The original XK - XP tank holds 11 gallons and when one is running a 305 cubic inch V8 motor that's a fairly limited amount of fuel.

Once you have salvaged a good fuel tank from an XR - XY Falcon, cut the filler spout from tank and the breather pipes that are along side it. This is best done by cutting a section from the top of the tank as seen in Fig 2 A. with a metal cutting jigsaw. With the section removed salvage the spout itself and a short piece of one of the breather pipes from the tank top. Now cut a piece of sheet steel to match the hole left in the top of the tank and welded it in, with the fuel tank 90% full of water. Add as much water to reduce the air volume in the tank without acting as a heat-sink for the welding area. Also tilt the tank so the bit you're welding is higher than the rest of the tank. You will also have to relocate a breather pipe to the same place as it is in the XK - XP tank Fig 2 C. It is best to make the hole for the breather before you start the welding of the hole left by the removal of the section containing filler spout and breathers. This will allow for expansion during welding, not that there is much.

Fig 1. The later model, XR - XY, fuel tank with the spare-wheel in the recess.

Once the old filler hole is welded over and cooled, tilt the tank so the water level is clear of the the breather pipe area then braze or weld in to position. When those two areas of welding are done reduce the water level a bit and rub some soapy water around your welds and blow in the breather pipe while looking for bubbles forming in the suds on the welds, like looking for a puncture in a tyre. If all is OK mark out the place for the new filler spout hole. There is a place close to the side of the sparewheel recess between some of the tank embossing that is suitable. Fig 2 B. The original XK - XP filler cap section of the fillerpipe will be used again but rotated a quarter of a turn clockwise, so as the end points towards the passenger side of the boot rather the floor, as it did. Hint Check for good alignment and ability to get the wheel in & out.

When you cut the hole for the spout make it about 4mm, or a quarter of an inch, less in diameter than the pipe. Then with a pair of Multigrips bend up the edge of the hole to form a lip around the hole. This will give you somewhere to braze the spout to the tank at. Also make sure the spout entrance is not too high from the top of the tank, fuel has to run in from the fuel cap pipe. Check height with XP tank or leave this part of the operation until the hole in the boot floor was been cut. Top the water up again before brazing or welding. Check the joint with soapy water and blowing in the filler with the breather blocked. If all is OK drain water and leave tank in the sun to dry out any water still in there. You may have to get another length of the rubber tube that connects the filler cap pipe to the spout if the old one is not long enough. New hose clamps are a good idea too.

Enlarging the hole in the floor of the XK - XP boot after removing the tank is straight forward. The rear face of the opening remains more or less the same, with the rear edge of the tank fitting as close to the rear panel of the car as possible. The sides, however have to be cut back quite a lot, almost up to the chassis rails box section. While the front edge of the floor is bent down to form a shelf.

Fig 2. Plan of the modifications, cutting and location of the 22 gallon tank.
The green is the cut line in the floor and the blue the fold line.

Mark a centre line on the floor of the boot and around the tank to divide them into left and right. Then measure the under side of the tank, from the centre line to each of the inner sides of the tank. The inner side being the side closest to the tank of the bolting lip around the tank. See green line in Fig 2. Transfer these measurement to the floor of the boot, from the point where the floor of the boot starts to slope up to the rear axle Fig 2. Z. back to the rear body panel. Do the same on the right side.

The sloping area of floor from point Z in Fig 2 to point Y in Fig 2 and the same section on the right side of the tank will be measured outside of the bolt lip plus 10mm on each side. The final marking is the fold line. Blue in Fig 2. The position of the this line is 80mm forward of the back of the boot lid support bracket. Fig 2 X.

With a metal cutting jigsaw or angle grinder cut along the cutlines and remove the unrequired sections. Hints: Leave as much sheet metal as possible attached to the fold line as this will give good leverage and aid the downward folding of the back shelf section and before you cut, check from below that you are not going to cut through any brakelines, wiring etc. It is well worth while to drill a small number of 3mm pilot holes just to see where your cut will come though.

Fold down the first fold in the back shelf section then clamp a piece of 40mm flat bar to that piece of sheet you just bent down and make another fold up to form the shelf. Remove the flat bar and trim the excess sheet metal. The new tank should now fit. All that remains to do is make some small additional shelf and side pieces from some of the scrap to fit around the rear corners of the sloping part of the floor area.

After drilling bolt holes, seat the tank on a bed of Sikaflex or Mastic and bolt the whole job together. Join up the filler, breather and outlet pipes. The original section of the steel outlet fuel line to the motor will require shortening slightly with a hacksaw. The fuel level sender unit from the XR - XY tank will work fine with the XK - XP gauge.

© BigH 2000

DISCLAIMER While this method has been tried and works, NO responsibility will be excepted by the Author, the Club or any of its Members.