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.