I have gone with the classic Aston-style fuel filler cap, which I ordered from Brasscraft at the same time as the windscreen. This comes in two parts: the lower mounting flange, which incorporates the locking fuel cap and the Aston-style cap itself, which screws onto the flange. I also ordered the unleaded fuel insert, which is needed to prevent a diesel fuel pump from being inserted into the fuel filler. This is inserted into the bottom of the mounting flange and held in place by a wire lock-ring.
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| The fuel filler-cap components |
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| The unleaded insert in place, and the wire lock-ring |
I located the centre of the recess in the AK body, using a machinist block to draw several chords across the circular recess, and drew a line perpendicular from the centre point of each chord, which should pass through the centre point of the recess. It does pay to do this several times, as I clearly had one line not lining up where it should!
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| Spot the line not playing ball! |
I used a 76mm diameter holesaw to form the hole for the mounting flange. I fitted the cap to the flange and checked that the cap hinge did not clash with the deeper edge of the recess. It did, so I used a file to open up the hole slightly towards the rear of the body.
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| Hole drilled... |
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...and the flange inserted.
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| Initially, the hinge hits the body when the cap is opened. |
The mounting flange comes undrilled, so the next step was to take a deep breath and get the drill out. Thankfully, the positions for the holes are marked out on the underside of the flange. I drilled the holes with a 4mm diameter bit using WD40 as a cutting lubricant.
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| Dimples identify the location of mounting holes |
The easy part was drilling the holes. The holes need to be countersunk on the top side of the flange. I had a metal countersinking bit but its diameter put it far too close to the threaded part of the flange for my comfort. I've seen on other build blogs people use an 8mm drill bit to form the countersink; i tried that but it left a very jagged finish.
I ended up buying a cheap metal countersink set from that well known internet auction site, which had bits of varying diameter, plus a round ended carbide cutter. I used an 8mm diameter countersink bit first and then used the round end carbide cutter to smooth the rough edges.
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| My usual metal countersink bit would not align with the hole |
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| A smaller countersink bit and a rounded carbide bit did the job |
I did a test on the underside of the flange to make sure I was happy with the finished result before countersinking and rounding off all the holes on the top side of the flange.
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| All holes countersunk |
With the cap screwed onto the flange, I could then align the cap so that it was a) positioned correctly for the IVA requirements and b) not fouling on the bodywork when the cap was opened.
I could then mark the positions of the holes and drill them out for the 4mm countersunk mounting screws.
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| Mounting holes drilled... |
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| ...and flange secured with M4 countersunk screws |
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| Cap installed and in the correct orientation |
Another top tip - when marking out the locations for the mounting bolts, make sure the cap is secured tightly onto the flange. I thought I had it on tight enough, but when I first secured the flange and screwed the cap on, I could tighten it an extra 20 degrees or so from where I had it previously. As a result I had to drill all the mounting bolt holes again.
Next up was to connect the filler cap to the fuel tank. The fuel filler hose is 51mm diameter reinforced ultra flexible hose from Car Builder Solutions. I used a spare length of braided fuel line to connect to the vent on the tank, which was connected to an alloy T-piece pipe connector ordered from eBay.
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| Hole drilled for fuel filler pipe using a 50mm holesaw |
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| Fuel filler hose and vent installed in boot... |
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| ...and under the rear wheel arch |
I need to get some hose ends for the vent hose to complete the job, but until then, that's another thing crossed off the long to-do list!
