custom made aluminium petrol tank.

[bill griffiths]

Before my Plus 2 was destroyed by fire about three years ago I had endured for 39 years the stain
of petrol around the filler cap.
I have read numerous posts but have reached the conclusion that the best solution for me is to design
and construct an aluminium tank. I would much appreciate any comment as to any aspect I have failed to take into account.
In simple terms the new tank will be at a maximum height about 4" lower than the existing one.
There then may be useable room above it for packing small items in the boot.
This will lose about 24 litres of fuel.
This will be a little more than compensated by extending the new tank rearwards, downwards and lengthways
so it extends, respectively, back to the rear vertical extremities of the square section on either side of the boot (about 9.5 inches) ; down to a height just above the battery which will also allow the spare to be slid underneath the protrusion, and out to the maximum width between the two square sections as above being about 41".
This will give vertical access for the filler, the top of the tank being about 4" beneath it.
The only issue I have seen so far is how to best to provide for the radio antenna!
The construction will be fairly simple and, once trimmed, only noticed by those who investigate the cause of the
unblemished paint on the nearside rear mudguard!
Regards,
Bill

[wotsisname]

I am trying to picture how the boot floor would be fitted and if the battery will come out. ( I have an early +2, so the boot may be
different). Also will you be able to fit the tank.? I think I would make a dummy one from thick cardboard or thin ply first.

[bill griffiths]

Good points, but all now attended to.
On the off side I shall stop the tank 4" before the side of the boot to allow for the electrical aerial.
The electric fuel pump will sit below the tank extension. I was in error with the extent to which the
tank extends rearwards; it is only about 4.5" but enough to compensate for the loss of volume caused by reducing the height of the tank by about 4".
It is that reduction which enables the tank to be filled with the filler almost directly above the top of the extension, with just a slight bend towards the off side of perhaps 2".
I calculate a loss of about 22 litres by reducing the height, but with a gain of about 26 litres in the rear, deeper slab.
And the weight of the fuel is lower, the height of the boot floor remains the same, the tank is easily installed and removed and there is, under the rear parcel shelf and above the tank, a handy 4.5" shelf!
I shall install the fuel gauge sensor in the off side end of the tank, adjacent to the aerial and with the float running athwartships. The total depth of the tank overall will be about the same.
I went through the same sort of exercise with my Talbot 110 some years ago...to avoid having to remove the petrol tank in order to remove the rear end in order to remove the pre selector gearbox in order to remove the engine.....
and it went as planned!
Regards,
Bill

[gus]

I had thought of a mod such as this if I was to design a Plus Two convertible, to make room for the top....

If it just the leaking cap, I cut a thicker piece of rubber for the gasket some 30 years ago, and it doesn't leak.

[mbell]

I'd recommend making a card board version first and test fitting it. I found it very tight fitting the standard tank via the boot, your reduced height may make it a much easier fit but it's still a large object going thou a relatively small hole. So worth checking first.

[bill griffiths]

The tank is almost complete.
It fits with the boot in place, and leaves room between its top and the underside of the rear parcel shelf for a suit pack! It does reduce the depth of the boot by a few inches. Capacity is the same as the original.
Regards
Bill

[alan.barker]

You have done a fantastic job and imho better than the original.
I imagine you have put some baffles in the Tank.
Would it have been easier to fit the float sensor from a hole in the top. Perhaps also the outlet at the back to have access from inside the boot and not a banjo fitting underneath.
Alan

[bill griffiths]

Thanks, Alan.
The tank is baffled.
Sender is positioned where it can most easily be accessed.
Outlet is into boot space via a stop cock to an SU pump positioned under the tank.
Yet to be installed are air bleeds from the top rear at each end of the tank, each running to the bottom of a small tank under the driver's side air intake (just behind the upper seat belt retractor) and with a line from there to under the car. (In case it ever fills from expansion after the ultimate top up in the Tasmania Winter followed by a quick drive to Queensland!)
Also, a horizontal strip along the tank's rear bottom edge to locate the bottom of the vertical panel at the back of the boot, (which also supports the rear parcel shelf,) and the boot floors.
Dimensions are available if any one would like them.
Regards,
Bill

[alan.barker]

Hi Bill,
you've answer my questions and it's a well thought out design.
When i had my last +2 i got fed up with the garage stinking of petrol so one day i put plugs in the 2 breathers near the back wheels. The next day i returned to the garage and there was lots of petrol coming out of the filler cap because of expansion in the tank.
The ORIGINAL Lotus design of the fuel tank for +2s is not very good. I don't know if they let an apprentice design it
On my Elan Sprint never a problem and designed correctly.
I also have 2 TVRs a 3000S and 3000M with electric pumps fitted near the petrol tanks. I have used Huco Pumps low pressure and very quiet .
Alan

[bill griffiths]

Attached (and by the way, this forum is a joy compared with doing battle with the AMOC
variety!!) is a picture of what I was sent (twice) when I asked for the rubber which goes
between the body and the filler cap.
It looks silly when fitted! And would most likely let the water in.
I had previously used an O ring but they are too hard to be likely to compress to make a seal.
A petrol proof sealant is an alternative.
However, best perhaps a soft square section O ring?
Any thoughts would be welcome!
Regards,
Bill

[wotsisname]

Bill, I'm not sure what you mean here. This looks like the standard item. Imho it fits fine ( once the shell was relieved due to crack repairs and paint). I'm not aware of owners complaining that water ( or fuel) enters the boot here ( I'm ducking right now, just in case). I am of course now thinking... Are you using a standard neck ?
Adrian

[alan.barker]

On my +2 and Elan Sprint i have used "sjsportscars" FUEL FILLER NECK GOMMET part X046L6001Z about ?11 + vat.
Very good fit with standard dia fuel filler neck. Put grommet in hole in body first then fitted tank.
Alan

[bill griffiths]

Buoyed by Forum responses I determined that the grommet would fit!
I carefully held apart the upper and lower sections and used a small grinding wheel on my dremmel
to reduce the internal diameter. Previously, it was quite impossible to insert the grommet into the hole for the
petrol filler.
This may have been because the body was, at some stage (after the car was pulled apart 20 years ago) tissue
coated, although there was no sign of that where I was attempting to fit the grommet.
Inching..or the metric equivalent perhaps.. deeper between the lips and testing every few minutes, progress was slowly made, and eventually the grommet fitted.
Regards,
Bill

[The Veg]

Looks like the grommet I got from Dave Bean. At first I could fit it to the filler OR the body, but not both...until I remembered that lubrication may help. A good slather of Vaseline made it got together easily, as it did getting the not-very-stretchy silicone cooling-hoses onto the spigots on my former Esprit. Once installed it looked right.

[wotsisname]

Good when it comes together.!..

maybe a bit late now... but for the future reader ?
When I had the same issue (see earlier answer) , I figured the hole was too small. The "deck" under the rear screen required a bit of work by the paint shop.. lots of cracks around the hinges, filler neck, etc.
I fitted the grommet to the neck and measured the diameter of the narrow point of the grommet. I then cut a circle from cardboard and used a dremell to ease the hole until the cardboard circle was a nice (but loose) fit. Before grinding I [separately] trialed the grommet and the neck (with cap fitted) in the hole to get a feel for which bits needed a bit more relief / how it would sit.