This blog is intended to document the build of my Gardner Douglas Mk4 Cobra; partly as IVA evidence, bit primarily to help others learn from my mistakes and/or successes.

I will endeavour to post as often as possible, with a view to entering a single post for a particular element of the build process, however inevitably some things may not be completed in one go. All posts will be tagged so it should be easy enough to find the information you seek.

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Saturday, 9 April 2016

Front wiring loom

The front loom has been a bit of a puzzle, especially within the cockpit area. I started by identifying and labelling the various parts of the loom using a combination of GDs wiring diagrams and the written instructions. Although this isn't difficult, it is time consuming but definitely time well spent and it certainly helped make sense of how it would be routed.

The standard GD method routes the front part of the loom out in to the engine bay through a 44mm grommet with the engine loom connectors, it then goes under the lip of the bonnet opening. I want to keep the engine bay as tidy as possible so I altered this slightly.

I pulled the front part of the loom (lights, radiator fan and horn) back through the big grommet leaving just the two engine loom plugs and the earth leads to go through the grommet. I then drilled a 20mm hole above and right of the heater ducts (looking forward) and routed the front part of the loom through the wheel arch compartment before going through the inner wing and appearing under the lip in the engine bay.

The loom then splits adjacent to the bonnet hinge; headlights/indicator/side repeater back through the nearside inner wing to the left and the rest to right under the nose cone and through the offside inner wing. The horn lead sits on the engine bay side of the nearside inner wing and the radiator fan cable hangs down in the middle under the nose cone.

Within the cockpit the relays have been mounted upside down in the nearside footwell and the heater fan & battery cable fed through the same hole as the front part of the loom in to the nearside wheel arch compartment.

Grommets have been used where the loom passes through bulkheads and it's all held in place with P-clips.

Relay block fitted with self tappers, just spotted that it's not level so adjustments necessary 

Nearside wheel arch. Head and side light cables to the left, side repeater cable going from left to right

Loom along inner nearside wing

Loom across nose cone, the cable dangling down is for the radiator fan

Friday, 8 April 2016


Before I could install the front wiring loom I needed to underseal the front wheel arches and nose cone. I bought Hammerite Underbody Seal from Halfords (I have a trade card :-D) and dug out an old paint brush.

Every edge was masked off to avoid having to clean it off afterwards, this took ages but preperation time is seldom wasted. When I opened the tin I thought I must have a duff batch as it was stiff, I expected it to be like a thick paint that would set hard. It turns out, it's supposed to be the consistency of a paste.

The instructions say to apply with a brush up to 2mm thick however I applied it thinner and will go back for a second coat, hopefully this will give me a better finish. It's quite hard work due to the thickness and working mostly upside down but the front wheel arches and nose cone have been done and the rear arches have been masked off ready. If I have enough left after that I may do the rear axle tunnel too.

I also bought a spray can of Hammerite Stone Chip Shield which I used for the lower sills.

Pretty thick stuff

I went through quite a bit of masking tape

Offside wheel arch after first coat

Nose cone after first coat

Sills sprayed with two coats 

Thursday, 7 April 2016

Accelerator pedal

The GM LS wiring loom I have comes with an electronic accelerator pedal but there isn't enough room to install it next to the pedal box so some creativity had to happen.

Andy from GD had mentioned something about mounting it on the other side and connecting it to the accelerator. I first cut the pedal off ensuring I left as much of the lever arm on as would fit within the wheel arch compartment to give the most amount of travel. I also had to modify the shape of it to allow the clevis to fit. It was then offered up, the holes marked and drilled in the bulkhead.

To remove the accelerator pedal I had to loosen all the pedal box mounting bolts which is easier said than done, but I manged it but putting one are through the footwell extension hole. Once removed a filed a couple of flats on the end pedal arm and drilled a 6.5mm hole for the clevis pin. The pedal was bolted back on but the 20mm hole I had drilled in the bulkhead for the turnbuckle wasn't quite right so this was extended down.

The turnbuckle I had was a little short so it was extended with some M6 threaded stainless rod an extension nut. It was then connected and adjusted so the accelerator pedal is the same height as the others.

I haven't ended up with quite as much travel as I'd hoped so I may have to move the turnbuckle fixing down the pedal arm later.

Modified GM accelerator pedal 

Modified GD accelerator pedal 

Turnbuckle connected in footwell 

Modified GM pedal in wheel arch compartment, thete is still plenty of room to get the plug in

Heater box take 2

If you've read my previous post you'll now know how not to fit the heater box! To repair this first effort I sellotaped over a small piece of plywood and taped that over the holes in the passenger footwell, then filled from other side with P40.

This time, I marked the centre of the heater on the lower rear edge the offered it into position before dismantling it, I then marked across the bottom edge and transferred the centre line on to the body.

The heater was again taken apart and the empty box held in position using the marks made in the previous step, I then sprayed through fan mounting hole with some primer I had lying around. This outlined a rectangle and screw holes where the outlets fit.

Two of the holes were pilot drilled which allowed me to fix the outlet ports to the footwell bulkhead with self tappers and mark the holes. These were then drilled out from the footwell side.

To mark the mounting bolt holes I placed a few layers of masking tape on the front of the bulkhead and; with the outlets installed and mounting bolts screwed in from the inside, pressed the box in to position. This was enough to mark the tape so these were drilled out to 10mm to give me a bit of wiggle room.

Now the heater can be reassembled and bolted in position to mark the heater hose outlets. I had already pilot drilled the holes for the battery cables so used the top one of these as a reference to measure from to the straight outlet. These measurements were transferred to the engine bay side and the first hole pilot drilled. I then measured 65mm rearwards from the other outlet and pilot drilled again, the holes will be opened out fully when the engine bay bulkhead has been gelled.

The heater has been removed again for now while install the wiring loom.

Mounting bolts inserted wrong way around to mark bulkhead

Installed as seen from footwell, you can see how far out I was the first time! 

Installed from wheel arch compartment, I used the upper of the two battery cable holes on the left to measure from for the outlets

Tuesday, 5 April 2016

Heater box take 1...

So this was my first major cock up on the build, thankfully it's only inside the battery/heater compartment and not on the outside!

The manual states that the heater needs to be mounted as high up and as far outboard as possible which makes perfect sense. I started by dismantling the heater so I was left with an empty box with no ends on, four M8 rivnuts (I would have used M6 but the nozzle for my tool is broken) were installed ensuring the bottom two wouldn't fould the heater matrix.

I then made a cardboard template which was offered up as high and outboard as possible, holes marked on the bulkhead which were then drilled out. I then put the two outlets back on the box and made sure they fit which they did, great I thought.

What I didn't consider was the fact that when the matrix is back in the outlet pipes protrude inboard and prevent the whole assembly going high enough, so my holes are too high.....doh!

These will need filling and I'll start again....

Heater box fully assembled 

Heater box fully disassembled 

Cardboard template put in wrong position, do copy this! 

Even worse, loads of holes in the wrong place, out with the P40

Pedal Box

The GD manual suggests lining the top of the pedal box up with the lip in the engine bay but I fitted mine about 15mm down, mainly incase my wife ever drives it!

I started by marking a horizontal line with a spirit level where GD recommend then measured down from there. The pedal box was then dissassembled so that I could more easily used the casting to mark the holes. The casting was offered up as far left as possible; making sure enough room was left for the left had nut, and one of lower bolt holes marked.

This first hole was drilled then the casting bolted in place, this allowed any fine tuning of level before the other holes were marked abd drilled. The casting was removed and the remainder of the holes drilled, I didn't have the right size holesaw for the master cylinders so these were cut small and opened out with die grinder.

The pedal box was reassembled and and the brake bias bar installed. I measured between the centres of the master cylinder holes which gave 62mm so the two clevis' were set 62mm apart and equidistant from the pivot. These will be set and locked later,  I'm just not quite sure by who!

Starting with the clutch cylinder the pedal box was bolted in place, the brake cylinders followed. The two brake cylinders are different sizes internally (0.70" and 0.75") so it's worth taking note of which one has been put where.  To get the right pedal height and clearance from the casting about 6mm was trimmed off the end of each brack cylinder thread. I then adjusted the clutch clevis to give a similar position to the brake pedal.

As I'm going to be using an LS engine I will be using the electronic throttle so a modified GM throttle pedal will be installed horizontally on the other side of the bulkhead. I am waiting for the postman to deliver a turnbuckle to finish this but it will mean taking the pedal box off again to drill the brake pedal arm as there's not enough room to get it off in situ.

The manual suggest placing the clutch and brake reservoirs in the engine bay and running hoses down to the master cylinders but to keep the engine bay uncluttered I'll install mine above the master cylinders. The clutch kit comes with two different reservoir sizes and various mounting options, I've placed the smaller one directly on top of the cylinder. I need to make a bracket to fix the brake reservoir to the bulkhead.

GD recommended height of pedal box, mine ended up 15mm lower

Checking level after first two holes drilled

All holes marked reading for drilling 

Pedal box installed

Master cylinders installed 
Safety first! 

Footwell extension

I had my Son down over Easter so it was the perfect time to tackle the pedal box as it needs a second pair of hands (unless you're a descendant of Stretch Armstrong or Gadget Man!).

The first thing to do was cut out the opening for the footwell extension as this will provide additional access. The extension piece was trimmed around the lip which was pre-marked then offered up to the car from inside the engine bay. I drew around it to mark the extremities on fhe body, then measured in the width of the lip (25mm) to mark the cut lines.

I used an air die grinder to cut just inside the line, final filing will be done once the extension is fixed in place. I then marked and drilled 6 holes in the extension and installed M5 rivnuts. These holes were transferred to the body and drilled, the extension will be fitted later with either silicone sealant or a foam/rubber gasket.

Extension taped in position ready for holes to be drilled for rivnuts

Extension from inside, the edges will be filed to match the profile of later


Now that the light plinths were polished I couldn't help but bolt some bits on the outside of the car.

This was a nice and simply job so took less than an hour to install the six small lights (2 x front indicators, 2 x rear indicators and 2 x rear stop/tail), the headlights haven't turned up yet so will be fitted later. I want to keep the car looking clean and simple on the outside so I bought smoked lens LED landrover defender lamps rather than the classic lucas style coloured ones.

The centres were predrilled from GD which I double checked were centred then marked the centre lines vertically and horizontally. The holes were then opened uo to 20mm to allow the plugs to fit through. I then positioned the lights so there was 10mm to the edge of the plinth around the edge then marked the mounting holes with a drill bit.

These were pilot drilled for the self tapper screws, these will be replaced with M4 stainless button heads and nyloc nuts when the post arrives. They will be wired uo when the loom goes in.

Centre holes predrilled from GD

Horizontal & vertical centre lines marked and holes opened up 

Close up of rear lights

Rear lights fitted 

Front side lights fitted, headlights in the post. 

Flash lines part 2

After removing the worst of the flash lines all around with a Stanley blade, the rear offside quarter panel was sanded with P400, P800, P1200 and P2000 which left a matt finish.  At that point I had no polisher so I didn't want to di any more until that arrived and I proved to myself that it would polish up ok.

The polisher along with some G3 and G10 arrived so I set to it. Most people have said how much mess it makes, but after watching the 'how to' video on the Farecla website I didn't seem to have too much trouble. It basically says to dampen the mop (rather than wet it), apply a small amount of compound to the edge of the mop then spread it over the area to be polished. The key here is to do a small area at a time.

After the G3, the rear quarter panel looked much better so I continued on rubbing down the rest of the flash lines. I used plenty of water and a combination of a cork block and rubber block for the larger flatter areas and a piece of closed cell foam for the small awkwards areas, primarily around the doors.

Once finished with the wet and dry I washed everything down with clean water then out came the polisher and G3 again. I  have only polished the areas that were sanded as yet with G3, I will do the whole car again later.

I can't say I particularly enjoyed the process as it is slow and laborious so I tackled it in manageable chunks, interspersed with other more interesting bits. It is very rewarding though to see those lines disappear and the shine return.

There are quite a few gel repairs to be done but that will have to wait for another day... 

Rear quarter panel after G3

Front wing after G3