Building our AC Cobra 289 LeMan

The metal cladding heatshields for the engine bay is something we’ve been working on for some time. Fortunately we have brother in law Phil Wilson who has an engineering, design and CAD (computer aided design) company in Leeds called Slipstream Design. They specialise in CAD engineering projects and prototyping of all shapes and sizes and following a conversation with Phil one weekend, we thought it would be amazing to design up exact CAD specs of the heatshields and get them manufactured via laser cutting engineering making them a perfect fit for the Hawks Cobra 289 body.

Mark being a super perfectionist and having an eye for the details, this idea really appealed as it felt a bit like we have brought a small amount of amazing F1 style precision technology and engineering to our Cobra 289.

It all started in a more low tech way with me and Mark both working up rough paper templates directly from the Cobra engine bay. We then sent these off to Dale at Slipstream Design to translate onto the computer and produce and exact specs requirements. He then sent us back the drawings which Mark could print full size at work to recheck against the Cobra body. We had to go through this process a few times with minor tweaks and changes.

We originally planned the inner wing sections to only fit the inner plain of the engine bay, as you can see from the visuals below. However, after inspecting Andy Gordons FIA Cobra at the Silverstone show back in August, we decided to make alterations to these panels to fit them nicely round the corner of the wheel arches. More on this in the next post.

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Mark decided to add some extra fibre glass to the floor where I had made the cut out for the pedal box. He cut a piece of fibre glass matt to bridged from the inner wing to the pedal box floor. This is mainly to add some extra strength to the floor but also to level out the lip connecting the inner wing unit to the peddlebox. He added a bit more on the pedal box floor so the surface is now level with the outside. We will probably finish it off by painting it white to match the peddlebox.

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It’s perfectly OK to leave the engine bay as it is, although the original Cobras had white footwells inside the engine bays. We are taking an educated guess this may have had something to do with combating and reflecting the heat coming from the engine in the original racing cars. We of course are keen to keep as much authenticity as we can on our build, so with that in mind the footwell simply had to be white. Firstly we keyed the gel coat to get a rough enough surface for the paint. We then wiped the the surface down with water and sponge to remove as much dust as possible before we started to carefully apply and cover with white spray paint. It pays to be patient with the coats and not spraying to readerly to avoid any drips. Annoyingly we got 1 or 2 drips which we had to then let dry before sanding down and spraying over again. 2 cans of white primer gave us approximately 4 coats. The pictures show the engine bay with only primer coats. We will be cladding most of the engine bay with sheet aluminium anyway but before that we will give the footwells a final few coats with a gloss white to finish it off nicely before fitting the claddling (heat shields) to the rest of the engine bay. More to come on that in later posts.

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Due to the modification Mark had made to the peddlebox by wielding a new flange around the edge, we had to spent a couple of hours cutting and extending the hole. The modifications now allow the peddlebox to fit completely flush with the outside of the footwells and make the final job inside the engine bay really tidy. We made a cardboard template to get the shape and as before used a hacksaw to cut the hole then finished by filing the edges to get them straight and smooth.

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After seeing Andy Gordons FIA Cobra at the Silverstone show, Mark decided he’d like to modify the peddlebox and weld an extra flange around the edge for extra support as well as getting a really good seal and making it look really tidy inside the engine bay. He stepped the flange back the thickness of the fibre glass in the foot wells so when it is fitted, it will sit perfectly flush on the outside surface inside the engine bay. When we original cut out the hole we stepped it in 1cm to create a flange with the fibre glass. Now this isn’t required, we will extend the hole slightly to the exact size of the original peddle box.


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After cutting the side vetns, next was the peddle box hole. This was a little more fiddly due to its position at the end of the foot well. Again the position for the hole was marked into the glass fibre body, so using this as a guide, we got to work marking it up using masking tape.

TIP… Next, and importantly, use a second line of masking tape to mark the hole approximately 1cm inside the original line. This will allow a small lip behind the peddle box that can be sealed cleanly when you fit the peddle box and master cylinder.

Once all marked up we drilled the corners, then using a small saw, cut around the edges marked by the second line of masking tape.

Other extras we might consider.

Once again after inspecting some of the beautiful 289 Register members cars at the Silverstone show, we have decided what we might do is wield an extra metal flange around the peddle box unit for extra support. More on this later.

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First real job was to cut the holes in the glass fibre body for both the side vents and peddle box. We started with the side vents. The body arrived with the vent shape and position already embossed in, so first we ran a marker pen around the edge of the emboss to get the line to cut to, then making smaller drill holes to use as a guide for a bigger hole cutter tool. This left us with a the rough hole, which we then  filed back to the marker pen line. This took some time, but this is not something to be rushed. Having got the holes reasonably neat and tidy we decided we would stop there and leave the job of getting them A1 perfect to the professionals when we finally get the car into the paint shop. This decision was confirmed the right one by a number of 289 Register members we spoke to at the Silverstone classic show on 22nd July, who said they did much the same when doing their builds. We next need to fix and fit the side vents in place. We’ll do this later.

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As we have now got the rolling chassis to a reasonably finished state, we decided to put some time into starting the body and getting it ready to put back onto the chassis.. There are 4 main jobs we plan to get done before this can happen.

1. cutting the holes and fitting the side vents, - link to post
2. cutting the hole for the peddle box – link to post (actually fitting of the peddle box and master cylinder will be done once the body and chassis are together),
3. painting the engine bay and peddle box white – link to post (matching the appearance of the original 289 Cobra engine bays)
4. manufacture and fit the engine bay heat shields (much more details to come on the heat shields)

Working with glass fibre is quite a messy and dusty business and would highly recommend wearing a face mask for these jobs.

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