Le Mans Alloy Flip Fuel Filler Cap.

To my mind, an alloy Le Mans style of fuel filler cap really looks the part on a well presented Lotus elan.

If during restoration the thought of not having an original elan fuel filler cap stresses you out a bit, then the addition of an after market cap such as a polished alloy Le Mans flip type of cap shouldn’t be aesthetically incorrect, in fact I would go as far to say that they look a whole lot better than the standard item as supplied by the Lotus factory, but if you’re aim is to restore your elan as per original, then you have no option but to source the original, or at least a reproduction item.

This short article illustrates the reason why the Le Mans alloy fuel filler cap was chosen for the S2 elan rebuild.

By the way, in the image above, take note that the rear boot hinge is a cast alloy item, this conversion was done during the most recent restoration completed about four years ago. the cast alloy boot hinges was something we did during the restoration project, but we don’t produce them in numbers.

OK, back to the fuel filler, as mentioned above, if the original item cant be accounted for, it is not difficult to employ a high quality after market item.

So lets look at how this was achieved.

There many many types of polished alloy Le Mans quick flip fuel cap fillers, they all look the part, but some are quite large, while others look too small, the one pictured above and further on in this article is about 3.34″ Dia, or 85mm, and for the size of the elan it looks about right.

But to install one of these on the elan, there is work to do, it is not just a matter of out with the old and in with the new. The existing fuel cap filler access hole in the body does not need much in the way of modification, all that is required is the four 3/16″ holes drilled to mount the fuel filler base to the body, but first you need to make the mounting base plate and the matching sheet metal holding ring that is placed underneath (Inside the boot).

So first off, lets take a look at the details of this project.

What the assembly consists of:

• Purchase one alloy Le Mans type of fuel filler cap (There are several types) The cap above is 85mm Dia.
• The alloy flip type cap also comes with a threaded brass base and an inner ring.
• Machine x 1 metal flange mounting ring.
• Threaded brass ring is required to be soldered to pipe extender.
• Short piece of exhaust pipe cut and joined (welded) to create an approx 12 to 14Deg bend in order to connect correctly with the rubber hose extending upwards from the fuel tank filler neck.

The grey metal ring at the bottom of the photo above is mounted below the cap, inside of the boot, the rubber hose filler tube connected to the tank passes through the ring.

Note: That the ring has four 3/16″UNC nuts brazed to the outer edges. Captive nuts simplify the installation when access can be difficult, we employ them where ever we can, but please keep in mind that the holes in both plates must be marked and drilled together, otherwise nothing will line up during assembly, so when drilling, make sure to witness mark the two items in some way so that they can be aligned during assembly.

The flanged carrier mounting base is machined from a short piece of thick walled hollow bar. (Yes, you will need access to lathe for this project). The flange could also be machined in two parts and silver brazed together.

If the writer was doing this project again, the flange diameter would be made larger, the outer flange OD in the pictures is 95mm or 3  3/8″, the OD could be made to 99mm with out encroaching on the rear lip of a hard top or a soft top, the best thing is to check dimensions with your project.

There are four 3/16″ UNC socket head cap screws to fasten the assembly to the body. The cap screws have been machined and finished to a neat round head, then chromed, make sure also to use small stainless flat washers, which will prevent the paint lifting (Squeezed) on the flange. It is the little touches that give a professional finish to any project.

The sheet metal ring has four nuts brazed to the holes that match the upper flange, make sure to mark both items to make it easy to align the bolt holes during assembly. As always you should carry out a “dry run” assembly before anything is painted just to make sure that everything goes together as it should, because there could be small issues that require correction before the final finish painting is performed.

There are about four pieces that go to make up the fuel cap base shown in the photo above. The pipe extender which engages with the rubber fuel filler hose, is just a piece of exhaust pipe which is the correct diameter to match the ID of the hose.

The extender is brazed to the upper flange mount. But inside the top, two brass sleeves are visible, the inner sleeve is soldered to the steel pipe, and the outer sleeve is soldered to the inner sleeve.

Note the thread, the alloy cap and the small base are actually screwed to the threaded base. Notice also there is a small hole drilled into the brass sleeve, the recessed hole is designed for a special grub screw to be screwed in to lock the alloy cap in place which will prevent theft should some low life in the know attempt to unscrew and keep your lovely polished alloy cap.

The steel pipe requires a kink or bend of about 12 Deg angle, this is an approximate guidance, because the actual angle wont be known until that part of the project is reached on your car, so be aware that the pipe has to be cut with a hacksaw at the correct angle and then welded back together again.

Another side view of the fuel filler base, this view gives a better idea about way the angle of the extender down tube and the cap mount sits.
The rubber hose is simply clamped to the short extender tube at installation.

The small mounting holes are drilled using the pre drilled flange as the drilling jig, (Cap orientated correctly) that way you know they are correct. When the assembly is installed make sure to place a light bead of RTV  between the body and the the flange to seal against ingress of water into the boot.

The boot floor has the usual carpet covered split boards, which are held down with countersunk screws which screw into rivnuts inserted into various metal brackets, this secures the boards and prevents annoying rattles in the car while travelling.

So far, the base has been secured to the body, the cap screws have been inserted and tightened into the captive nuts on the round but hidden plate. Captive screws save a lot of frustration and cussing where access with fingers and tools are difficult.

A couple of things to note here, the alloy LeMans cap screws onto the base, which is now fastened to the car body as described. The sealing ring prevents metal to metal binding. Also note the grub screw inserted between the two cap hinge lugs, the grub screw is tightened after installation to prevent theft or the cap working loose and becoming lost. Do not forget to tighten the grub screw.

Fuel filler caps do not come more beautiful than an Alloy Le Mans Type fuel filler, they get a lot of admiration from casual onlookers.
One drawback with Le Mans style fuel filler caps is that you cant lock them, well not the type above anyway, some types available today perhaps may have locking device, but then again, most elan owners don’t use them as daily drivers, the writer certainly does not, and most places it is driven to it is never really out of the owners sight, so if someone starts messing where they shouldn’t be, you can take action to make sure no harm is done to your pride and joy.

Most of the people admiring your elan will be decent enthusiast types, I have had many lengthy conversations with people who often say to me; “Love your elan” followed by “I used to own one, fantastic car to drive, and still wished I had it”.

So there you are, I nice bling project for you to attempt one day.