Aluminum Fuel Tank

NOTE: There is ONE tube shock conversion that has an upper bracket located inside the trunk next to the tank that interferes with placement of the tank. The green arrow points to the shock bracket and you can see how it's keeping the tank from moving to the dotted red line. Not all shock conversions have this bracket. I've had two different tube shock conversions on my car and the tank would have fit with no problem.

I don't do a whole lot of long distance driving but it doesn't take a real long drive to bring the stock tank down to 1/4 on the gas gauge........... and seeing as I've run out of gas twice at the 1/4 mark..... I figured there had to be something better. And then there's the annual trip to The British Invasion in Stowe Vermont where exits are 10 - 15 miles apart and there's not necessarily a gas station at the end of the exit ramp.

My plan was simple.........more capacity and in an aluminum tank that won't rust over time. The capacity of the stock tank seems to depend on what resource you're looking at. Two of my reference books say 13.5 gallons for '69-'72 and 12.9 gallons from '73 on. My driver's manual that came with the car says 11.4 gallons..... then factor in that no one in their right mind ever fills the stock tank all the way up......unless of course, you love the smell of gas permeating the cabin. Maybe the 11.4 capacity in my manual was Triumph's way of saying .... the tank may hold 13 gallons but don't even think about putting that much in it! Finally there was price......... a stock capacity aluminum tank from Moss was $620 and TRF was $700! And steel tanks weren't a whole lot cheaper.

NOTE: In 2018 Boyd Welding did a production run of about 10 tanks and one of the recipients did an accurate filling of the tank with water before he installed the tank..... to the bottom of the filler tube was exactly 15 gallons. My "math" estimates were 13.75 - 15.2 gallons. I'm glad to see it hit the 15 gallon mark.

I started with Dan Master's aluminum tank design for his V8 powered TR6........ a very nice tank but he modified the trunk to get an 18 gallon tank fitted. Then one of the 6-Pack Forum guys, Craig Kenyon came up with a very special design that incorporated a swirl pot and an external pump.

Craig's beautiful tank designed specially for his car and his needs.

He was kind enough to let me use his design as the basis for my design. I wanted a tank generic enough that it would easily fit any TR6 and possibly the TR4. The primary difference between the two tanks is that my design is shorter in height to make installation easier and I approached the mounting points a little differently. I also wanted to take advantage of the fact that the TR6 has floor openings for outlets on either side of the car. The "spirited" drivers out there have reported fuel starvation during sweeping corners when the tank was low on fuel. Putting an outlet bung on each side gives them the options of draining from both sides. They're a stock 1/4" NPT fitting so an unused one can just be plugged. I also wanted the tank equipped with a return line fitting and an evaporative canister fitting. If someone doesn't need them, they can just cap them. The last things were two baffles and, ideally, use of the stock TR6 sender unit.

But you don't just draw up a design and have Charlie the welder at the local garage bang one together for you. I started with the design and built a masonite mock up.

I used 1/4" masonite and wood strips to build the tank. The rectangular cut out is so the tank clears the diff hump

First cut out was too big so I brought it in 1" on all sides

So far it fits fine

It lies nicely behind the rear trunk panel supports and the interior trunk panel fits too.

View from inside the car.

Trunk View

It's 30" wide which leaves 1/4" gap on each side

Mocked up bracket - the arrow points to a construction mistake...... I laid the top on top of the sides which raised the overall height 1/4" which is a big deal. I re-cut it to recess inside the tank sides.

It fit right up to the edge of the trunk panel mounting points.

It's probably not absolutely necessary but I ended up cutting the two bottom tabs so the tank will slide between them instead of having to lift it over them.

There's an outlet hole on each side so you could have two bungs fitted and drain the tank from both sides..... and that's ugly old felt underlayment stuck to the hump. I loosely attached the bottom bracket to the tank mounting holes to get a feel for how it fit.

The mock up rested right on it so now I need to mark the holes and mount the bracket to the tank.

Now I know why Dan Masters' design didn't have any top mounting points......That double green arrow shows how little room there is to fit the tank and the tank is too big to tilt. The bracket needs to be about 2" tall to line up with the bracket hole. My solution is to have a threaded stud come up so you can drop the bracket over the stud once the tank is installed. After talking to Boyd Welding, they recommended a mounting pad with a threaded insert rather than a "weak" aluminum stud.

More to come after Christmas... the red sleigh is loaded and heading to MD on Sunday. The first week of January was pretty cold, so the 8th was my first day back in the garage. Now that I've got all the mounting brackets set, I bolted the "tank" in place to get the inlet and outlet hole locations......sometimes you have to get creative.....

Next was to trace around the tube....

Plumbing fittings were used to mock up the real fittings. This has the same 1" rise as the stock tank. I had to cut a hole in the rear of the "tank" to give me access to the various holes and bolts.

Everything seems to line up perfectly.

Two more plumbing fittings for the bottom of the tank. Most people will only need the one outlet on the left side of the car but some "aggressive" drivers might want two outlets so there's no fuel starvation in hard cornering.

Perfect!

And this is a stock hole on the passenger side that's filled with a rubber plug. No drilling required.

Now comes the scary part.........drawing all of this up with accurate measurements so that the tank can be made. And...............finding someone to build it for me.