Fitting the body

I was a bit worried about refitting the body and aligning it. I had made and fitted a non standard heater box and although I took loads of measurements first, I was worried I may have missed something. So the heater could have interfered with the fit. And I was also concerned about alignment because once the body was sitting on its sticky, grungy sealant, it would be difficult to slide it into position if I needed to.

Many hands make light work

So I decided to use the two bolt locations on the rear chassis rail that the body securing bolts go through as reference points and fit alignment pins into them. I drilled out the holes in the bottom of the chassis rail to take M8 rivnuts and then screwed long M8 bolts in from the bottom so they protruded out the top. I left one longer than the other to make fitting easier and made sure both bolts were perpendicular to the chassis rail.

Adding sealant to the chassis rails

So when it came to the time to fit the body, six of us lifted the body off the trestle it was resting on, manoeuvred it over the chassis and lowered the rear first onto the alignment pins. We then knew the body was in exactly the right position over the chassis so were able to lower the front down. It worked a treat and there was a good 15mm clearance between the heater box and the clutch bell housing so that was a bonus as well.....!! All the rest of the bolt holes lined up perfectly. The only issue I had was that the alternator interfered with the stainless steel cladding on the inner wheel arch. The witness Mark's on the cladding showed that this was an issue when the body was first fitted at AK. I have filed a small amount off the fins of the alternator which has given some clearance but whether this is sufficient when the engine is running remains to be seen.

Lifting the body on to the chassis

Once the  body was bolted up I removed the bolts that went through the scuttle hoop and the two in the rear chassis rail. In order to provide a good electrical connection between the body and the chassis I removed the powder coating from an enlarged area around the bolt head and nut and then reinserted the bolts using penny washers under both the bolt head and the nut. I tightened them all up again and put a coat of paint over the bolts, nuts and penny washers to ensure no water ingress so that earth remains good. A quick check with a multimeter showed a good connection between  body and chassis.

So it now looks like a Cobra again and I can start fitting her out. 

Back together again.

Many thanks to all the helpers who were successfully bribed with bacon butties for the occasion. The trestle has gone to a new home supporting another AK body which I am pleased about. Next job is the steering column.

Pedal Box, Brake and Clutch master cylinders

Fitting the pedal box itself was fairly straight forward. All the fixing holes lined up perfectly so with the help of an assistant it was bolted in place in no time at all. Strange thing is that I now seem to have someone claiming that they have built the car...........

One thing that needed to be thought about was how the brake lights would be operated. The two options are a hydraulic switch fitted somewhere along the brake pipes or a push switch operated by the brake pedal. As my brake lines were all fitted I chose the push switch on the brake pedal.However, the pedal box has no provision for this so a simple bracket was needed to mount it.

So, checking to see how far the brake pedal came back I fashioned a bracket to suit. Fortunately, the switch has a long mounting shaft with two nuts on it so the depth at which it sits in the bracket can be adjusted to suit. (An oversight here meant the whole pedal box had to come out again later....!!)

Brake light switch and bracket.

The bracket was bolted to the pedal box from the back of the box using countersunk screws and all appeared good.

Then the pedal box was fitted to the bulkhead and I could now fit the brake master cylinder and servo and the clutch master cylinder.

Brakes are pretty important...!! So I decided that I wanted to fit new items. So I found a brand new brake master cylinder and servo combo that fits a Rover 200/25/MG ZR. Well, it may do, but it doesn't fit an AK Cobra. The servo and master cylinder combo are too long to fit between the foot well and the offside front wheel arch. So that's for eBay and after some searching I have now got the correct combo comprising a used servo and new master cylinder fitted to the bulkhead and pedal box. (Lesson learnt: not all Rover 25 brake master cylinders are the same......)

Servo and Master Cylinders fitted

I have fitted flexi hoses to the master cylinders to connect up with the brake pipes running along the chassis rail. It took a little while to identify the thread in the brake master cylinder outlets but eventually identified them as  metric M12x1 (3/8 UNF in the Clutch M/C)

Fitting the brake M/C and servo gave rise to the oversight mentioned earlier. The extent to which the brake pedal returns is not determined (of course......doh...!!) by the pedal box but by the length of the brake M/C push rod. So my nicely made brake light switch bracket, even with the adjustment available in the brake light switch, resulted in a 5mm gap between the pedal and the switch meaning that the brake lights would always be on. No good. So to remove the bracket I had to remove the pedal box and to remove the pedal box I had to remove the brake and clutch M/C and servo. (I should have brought some of that 'right first time' culture back from work with me.........!!) Anyway, cylinders and servo removed, assistant recalled, pedal box out, and we're back to square one.

So, rather than make a new bracket, I decided to make a small modification to the brake pedal. At the point where the brake pedal makes contact with the brake light switch I drilled and tapped a hole to accept an M4 Pan head screw. This now makes contact with the brake light switch when the brake pedal is released and provides for further adjustment if ever needed in the future.

So, the very first bit of the Cobra is now working......!!  It's only a brake light switch but it's now fitted and adjusted so that contact is made (and the brake lights will switch on) with the smallest of pressure on the brake pedal.

Pedal Box in place.

There will be a few things to do around here yet. The steering column bush needs to go in and the throttle cable needs to be fitted to the right of the pedal box, plus the wiring to the brake light switch. It's a tight squeeze down there and I hope none of this will have to come out again anytime soon. (is that tempting fate..................??!!)

Propshaft.

Fitting the propshaft all seemed quite straightforward. The challenge was to make sure I get all the measurements right in the first place to send off the Bailey Morris to get propshaft made and balanced.

Bailey Morris supplied a form that I could put some key details in but I also did a drawing for them that I understood as well!!

Additional Drawing

Bailey Morris Form

I read various opinions about just how much of the slip yoke shaft should be protruding from the back of the gear box and therefore, how long the propshaft should be.The yoke is at the end of a splined shaft that slips over the splined output shaft of the gearbox. The length of the splines is something like 100mm to 120mm. The slip yoke cannot be inserted all the way  into the gearbox as there needs to be some float to allow for any potential movement between the gearbox and final drive. But it is not going to move any more than 5mm so that should be sufficient. But some comments were saying that there needed to be 25mm of yoke protruding from the end of the gearbox. That would mean that there is 20% or so less engagement of the output splines and given that there is 400hp+ transmitted through those splines I kinda thought that the greater engagement the better.

One of the reasons I can see for the 25mm allowance is to overcome a fitting issue. I had a long centring spigot in the middle of the final drive flange that stops the propshaft being manoeuvred into position once the slip yoke is inserted in the gearbox.

  












If you fit a shorter propshaft, you can slide the slip yoke right into the gearbox, then raise the propshaft flange at the final drive end over the centring spigot and slide the propshaft rearward over the spigot so that the propshaft flange and final drive flange meet. This would result in approx 25mm of slip yoke protruding out of the back of the gearbox (and a reduced engagement between the output splines).

I decided to keep the amount of shaft protruding to a minimum so in order to do that I took a disc cutter to the final drive spigot and shortened it so that there was just enough left to go through the propshaft flange to ensure it was centred. That was a lot easier than I thought and has left me with about 8mm of float in the propshaft that should be more than enough.

Propshaft float. The shiny bit between
the UJ and the gearbox

I had to use socket head screws to bolt the final drive and propshaft flanges together as there was insufficient clearance to get a normal bolt head passed the UJ. Even then I had to grind a flat on the screw head to get the clearance I needed.

So the propshaft is now fitted. 

It doesn't look right to have the level of mis-alignment between the gearbox and final drive but it appears it is standard for this build and not a problem. After all that's what Universal Joints are for but I must remember to keep them well lubricated.

Fuel pump and filter

The fuel pump and filter are next. They are fitted in the transmission tunnel, secured to the inner chassis rail. Access is much easier while the body is off so they are better fitted now.

I'm using an LS3 engine so need a high pressure pump that will deliver a constant 65 psi, controlled by a fuel pressure regulator. The Bosch 044 or equivalent is recommended. All the pumps instructions say that a pre-pump filter must  be used and that the pump should be no more than 600mm from the tank outlet. Achieving 600mm is a bit difficult with the AK if a pre filter is used but I didn't want to risk damaging the pump so I've had to compromise a bit.

I have pushed the filter as far back as I can on the  chassis rail, ensuring sufficient radius of the bend in the fuel pipe, and fitted the pump as close to it as I can, allowing for the connecting fuel hose to go around the angle in the chassis rail at that point. I've also replaced the fine cartridge filter inside the filter can with a 50 micron metal filter to minimise flow resistance. So I have about 750mm between the tank and the pump and have made a mental note that if I have fuelling issues in the future  that's the first thing to look at............!!

The filter is fitted with the spring clips provided, riveted into the chassis. The pump wasn't so easy because I didn't have a drill small enough to get in between the chassis rails to drill hole for the fixings. So I decided to drill the chassis rail right the way through from  the other side and fit rivnuts in that side. I then secured the pump by using long bolts through the chassis rail into the back of the rivnut. It works a treat and means its reasonably easy to remove the pump in future.

Rivnuts fitted in opposite side of chassis rail

I  need to decide now whether to put a fine filter down stream of the pump prior to the fuel rail. I think its probably worth doing. Injectors have some very fine jets in them.

Heater

AK recommend using either a heater from a Mk2 VW Polo or the Heat3 heater available from CBS Online. The original design allowed 'fresh' air from the engine bay to be blown through the heater matrix and into the passenger compartment for warmth and/or on to the windscreen for demisting.

However, recent IVA requirements have said that air cannot be drawn from a source of potential pollution, so 'fresh' air can no longer be drawn from the engine bay.  Taking it from the passenger compartment is the most straightforward alternative. This requires either end of the squirrel cage fan on the Polo heater motor that sits in the engine bay to be blanked off and a 40mm (ish) port to be fitted in the blanking plate to feed air in from the passenger compartment  via some suitable ducting.

I want to be able to use the Cobra through the winter in a 'reasonable' level of comfort so I have decided to use the alternative Heat3 heater. It has a larger heater matrix than the Polo heater and has two fan motors rather than just the one.

AK say that this heater can be installed in a similar way to the Polo heater. But there are now four fan motor ends to be blanked off and air ducting to be installed. So I looked to see if anyone else had used the Heat3 heater previously  and how it had been installed, but with no success. So I had to come up with a plan.

I thought that rather than blank off all the fan ends, a more elegant option would be to build a box around the heater to seal the entire heater assembly from the engine bay. I could then put ports for the ducting into the box and into each of the foot wells and duct air from the foot wells into the heater box.

However  with the body separated from the chassis  I didn't know how much clearance there was between the bulkhead where the heater is mounted and the chassis cross member and clutch bell housing. So using bolt holes that secure the body to the chassis as a reference point, I marked the position of the cross member and bell housing in the engine bay. This showed that clearance for the heater box would not be a problem.

I cut the basic shape of the heater box out of a piece of 600mm x 600mm x 0.8mm aluminium sheet. This would produce a box that would place the the front of the heater matrix approx 35mm into the passenger compartment and would still allow the AK plenum to be used. (Although its width is a bit tight for the Heat3.)

Openings were then cut for the heater hoses, air ducting and electrical connections, and the aluminium was folded to form the box. 

Corners were created with 20mm x 20mm Ali right angle section riveted to the sheet and grommets and air duct ports fitted.

Provision was made for the heater to be fitted into the box with 150mm M8 bolts. There will be  6mm spacers top and bottom made from 8mm i.d. fuel hose. The air ducting was added at this stage because it looked interesting...!!

With the heater contained in a box, I need to ensure that it is accessible if it requires any maintenance in the future. If I use the AK heater plenum in the passenger compartment that will be sealed around the edges so there will be no access from inside the car. So I will fix the heater box in place by bolting it into rivnuts in the bulkhead and sitting it on a rubber seal. This should keep the IVA man happy that no pollutants will be getting into the box and will allow me to remove the box in future if necessary. So the opening in the bulkhead for the matrix is now cut out and rivnuts fitted for the mounting bolts.

Finally, prior to fitting the heater box and matrix, ports for the air ducting have been fitted into the tops of the drivers and passengers foot wells.

So after giving the heater box a coat of paint, the heater was fitted to it with the two M8 x 150mm bolts and spacers and a strip of a medium density self adhesive foam strip was added to the flange that mates to the bulkhead. This provides the seal between engine bay and passenger compartment. The heater box was then bolted to the bulkhead with M5 bolts and air ducting fitted between the ports in the heater box and those in the passenger and driver foot wells.

Whilst I am not tackling the air ducting in the passenger compartment yet, I will have two options for the plenum when I come to it. First is the AK supplied air box that, with a bit of a tap, fits around the Heat3 matrix. I can now use this as the main seal is around the heater box so an air tight seal around the plenum is not as important. The second is the plenum with four moulded outlets that came with the heater. But that's for another day and I'll have a think about that and make my mind up when I'm doing the interior.

AK supplied plenum

Plenum supplied with Heat3 heater.

Collection

So, I've cheated a little bit.........

I've gone for a rolling chassis as a starting point. The stripping down and refurbishing on the two previous projects have reduced my appetite for doing all that stuff again

And I've compounded my cheating by having the engine and gearbox shipped to AK and bolted into the chassis so that the exhaust side pipes could be mated to the exhaust headers in the factory, avoiding me having to take it back there later. 

So the rolling chassis and body were collected from AK on 21st August 2018. Unfortunately, the planned five weeks of work in the house to fit a new kitchen and enlarge the garage lasted 15 weeks so there was no where to put the rolling chassis back in August. Fortunately a friend had room to store it so it was mid November before the Cobra turned up here in my garage in the back of a race trailer.

I knew that the first thing to be done was to separate the body from the chassis. When I visited Jon and Wendi in Peterborough, I measured up the body stands that AK had made and so prior to arrival I built something similar out of 2 x 2 with a set of 5" casters. I thought about hoisting the body above the chassis in the garage but decided that given I had a rolling chassis, the body and chassis would not be separated for too long so the body would happily sit on its stand on the driveway under a good quality car cover for a couple of months. (My plan is to refit the body in early April)

So the body now sits on the driveway and the chassis sits on stands in the garage and I'm sorting out what needs to be done before they are reunited. As far as I can see so far that includes:

• Fit heater
• Fit pedal box, brake servo, master cylinder and clutch master cylinder and connect clutch slave cylinder
• Fit fuel filter and pump
• Fit propshaft
• Check tighten all rolling chassis nuts, bolts and fixings.
• Fit exhaust headers
• Cut remaining openings in the bodyshell.
• Fill gearbox and diff with fluids (easier with body off)
• Paint inside of engine bay
• Refit and connect radiator
• Check for anything else...............!!

So its now time to start and the first job to tackle is the heater.

Introduction

1986 I think it was.

It all started then.................................

That's when I first came across a kit car in the form of the Dax Tojeiro Cobra. I wanted to build one. It looked beautiful. So much better than the Minis, Escorts, Vivas and even a Capri I had been driving in those days. Funds were too challenging back then. But I caught the bug and I wanted to build something.

I was living near Falmouth and not too far down the road in Plymouth was Marlin Sportscars. I was talking to my girlfriend (now wife) about building a Marlin and then, on my birthday I received a photograph album from her with a load of photos of the red Marlin Roadster demonstrator. She had sneaked off Plymouth, gone to Marlin, took a load of pics and put them in an album for me......!!

So in late 1987 I put my first Marlin on the road.

It was Morris Marina based with the old 'B' series engine and although I was never going to burn rubber in it, it was great fun. 

But what I really wanted was a Cobra. 

I sold the Marlin in the mid 90's and have never been able to track it down again since and I'm pretty sure the Marlin Owners Club have no record of it either.

Wind the clock forward to 2010 and I had done all sorts of sensible things in the intervening 23 years or so. Perhaps the less sensible thing I did though was mountain biking which meant that in June 2010 I was laid up with a broken collar bone and three broken ribs on my left hand side and an ulna collateral ligament torn off my thumb on my right hand side. So while idle I started, for no obvious reason, to wonder what Marlin were up to. Of course, unlike 1986 there was now the internet, and websites and stuff like that. So I had a peak at Marlin's website and Marlin were now doing a BMW based Sportster kit. The kit car bug bit again. Again I looked at Cobras but this time, I didn't have room to build one. So I built another Marlin and in June 2013, put it on the road.

This is a very different car to the first Marlin. Great handling. Great performance, and surprisingly comfortable on a long journey.

But I still wanted to build a Cobra.

So, in 2015, having had loads of fun with the Marlin, I decided that if I was going to build a Cobra it had to be done now. And finally, 3 1/2 years later, the bits are sitting in my recently enlarged garage and the build can begin.

This is an intro and I hope to keep the blog updated as the build progresses. The other Cobra build blogs on here have been a real godsend and encouragement and have already given me a lot of clues and answers as to how to approach things. I hope this blog will add my ten penneth to the picture and future builder will find something useful here.