The car needed to go on a weight saving program to make it as light as possible, or 'adding lightness' as Colin Chapman said.
Removing the sound damping material on the firewall inside the bonnet, as well as the damping and steel plate inside the passenger foot well saved 3.5kg.
Nylon door straps that only weigh a total of 64g were made and replaced the original door checks which weigh a total of 1.9kg – that’s almost half a kilogram each.
The aircon jockey pulley had never been removed from the engine until then – that weighed 1.2kg. It all added up and the goal was to try and find 100kg in saved weight.
A fellow competitor, who is obsessed about adding lightness, managed to bring the weight of his series 105 Alfa Giulia down to 850kg. He said that there is eventually nothing more that can be removed to save weight and that eventually money would have to be spent to do so, like replacing standard cast iron brake callipers with aluminium units, or buying fancy hollow camshafts instead of standard solid units.
Additional weight saving would later come from changing the front and rear windscreens, as well as the side windows to Lexan.
Further weight saving was done by removing the bonnet hinges and springs, removing the bonnet strengthening bars, cutting away the edges of the bonnet and drilling holes in the brace at the back of the bonnet. A new bonnet stay was made to keep the bonnet open using a piece of aluminium tube. Total weight saved was 2.2kg.
The insides of all four doors were cut out and holes were drilled in the bottom of the doors – the total weight saved was 6.8kg
The brackets for the spare wheel mounting in the boot were removed as well as the boot lid hinges and springs. Each spring weighed almost half a kilogram. All the unnecessary parts on the hinges were cut out and then holes were drilled to save weight.
The boot lock and striker were removed – unbelievably this weighed almost half a kilogram
The inner strengthening frame of the boot lid was cut out, which lightened the boot lid by 4 kg, from 15.9kg to 11.9kg. Two panels were also cut out of the rear boot panel.
All the weight saving so far amounted to 30kg.
The car was getting hot during the track test and it was recommended that two fans were used. That would have been a last resort as there was constant tension between wanting to keep the car looking as original as possible, but also wanting it to be a decent race car. One of the things that was essential was to reduce the under-bonnet heat, bearing in mind that the temperature gauge sender unit sits at the back of the cylinder head in a place where there is probably the least air flow. The historic racing regulations ban any louvres or vents in the bonnet unless it was there in period, so an alternative plan had to be made.
A system was devised to allow the under-bonnet heat to flow into the car's air box, from where it would be extracted. Two holes were cut out the firewall so that air could flow into the air box.
A hole was made in the bottom of the air box with a mounting bracket for an air duct.
A small cooling fan used on KTM motorcycles was attached to a mounting bracket which fitted inside the wheel well, using the original hole for the interior fan.
A ducting pipe was then connected to extract the air and worked well. Covers were made to fit over the original vent holes to block outside air from entering the air box
Theoretically all the hot under-bonnet air should be sucked out from the engine compartment and expelled into the wheel well. A separate switch was fitted to the centre console for the extractor fan.
The radiator was also shrouded to prevent any air from going around the radiator instead of through it.
A battery cut-out switch is a regulatory requirement in case of emergency. The cut-out switch must be able to be activated externally by a marshal if need be, so the simple solution is to have a cable attached to the switch lever, which can be pulled to move the switch into the off position. A cable was made and then fitted in place.
The front windscreen and rear window were removed and sent away to a company that manufactures Lexan canopies for helicopters and aeroplanes. Normally a rear window would be made of 3mm Lexan and screwed into place in the window frame, but the original window seals and trims were going to be used, so the windscreen and rear window were made from 6mm material. It would still be lighter than the original glass.
Using photos found on the internet, the auxiliary fuel tank was made.
To get the proportions right, a mock-up of the tank was made from cardboard, using various photos as a reference. The mock-up and drawings made from the mock-up were sent to a company to have the tank made
The Land Rover fuel filler and cap were found to match the internet photos of the fuel cap. The filler was straight but needed to cut and re-welded at an angle to line it up with the tank.