1975 ALFA ROMEO GT JUNIOR 'CLR'

This 1975 Alfa Romeo GT Junior Bertone ‘CLR’ (Carrera Lightweight Racing) is a unique and extreme track-focused but road-legal development of the popular 105 Series model, which has been built by a qualified aeronautical engineer to offer maximum performance in the lightest package possible.

It is powered by a Honda F20C inline-four, taken from an S2000, chosen for its advanced design and high engine speed capability. For the F20C, Honda engineers employed technology derived from the marque’s racing engines, including Fibre-Reinforced Metal cylinder liners (FRM) and molybdenum disulfide-coated piston skirts for reduced friction. The engine block is constructed of aluminium with a fibre-reinforced metal sleeve along with forged aluminium pistons.

High engine speed capability was the main focus of design with a rev limit of 9,000 rpm. Its relatively long stroke of 84 mm results in a mean piston speed of 4,965 ft/m, or 24.6 m/s, which was higher than any other production car to date.

The F20C engine also held the record for producing the highest specific power output for any mass-production naturally aspirated piston engine, at 123.5 HP/L, until Ferrari began production of the 458 Italia in 2010, which produced 124.5 HP/L. The success of the F20C engine led to it winning International Engine of the Year five times in its lifetime (from 2000 to 2004). In short, it is not hard to see why this remarkable powertrain was selected for a performance-focused built.

This engine has also been fitted with individual throttle bodies and is connected to a Honda S2000 six-speed manual transmission. This drives the rear wheels via a Mazda MX-5 Torsen limited-slip differential.

First registered on 15 January 1975, over the last 14 years this left-hand drive GT Junior has been completely transformed by its previous owners and current aeronautical engineer owner, who set about redesigning and reengineering the car, while remaining in line with FIA specifications.

The car was meticulously upgraded to aviation standards using a number of parts from the industry, including repurposed Saab jet fighter fuel tank components, door surrounds crafted from aircraft-grade titanium and helicopter window vents. A number of more traditional performance parts were also fitted, including the Honda S2000 engine and transmission mentioned above, custom suspension components and uprated brakes taken from a Seat Leon Cupra R and a Mitsubishi Lancer Evo VIII.

Phase two of the build was undertaken between October 2019 and the present day, with the car being converted for Europe-wide TÜV approval, comprising a raft of work to the engine, fuel system, chassis, bodywork, brakes, and the wiring harness. In short, almost every component on the car has been upgraded, with the only partly original element being the chassis, which has also been heavily modified.

The result of this, combined with this GT Junior’s fully stripped interior and composite panels is a kerb weight of just 874kg, making this already spritely Italian coupe a true featherweight flyer with an incredible road and track driving experience. Now complete and TÜV approved, the car is offered for sale to another enthusiast owner.

Even the most cursory glance over this unique Alfa Romeo’s bodywork will make it clear that the car is far from standard. From its vented bonnet to the aggressive bolt-on flared wheel arches, every element is purpose-built for performance.

The bodywork remains in good order, and while there are some imperfections in the Rosso Corsa paint, it is nothing that cannot be excused in a track-focused road racer. A simplified white Alfa Romeo logo adorns the roof, while the bonnet script, Quadrifoglio Verde wing emblems, and the racing roundels give this GT Junior a nostalgic appearance.

Its motorsport sliding plexiglass windows were also fitted with helicopter air vents, while the door surrounds are formed from aircraft-grade titanium, and the rear windows feature plexiglass NACA ducts for enhanced cooling in the cabin.

The car rides on a set of gold 16-inch Team Dynamics Pro Race 1.2 alloy wheels, and will also be supplied with two spare sets of wheels fitted with both dry and wet-weather tyres.

Fully stripped-out, the functional cabin features a pair of black Sparco Sprint bucket seats, which are in very good order and feature standard seatbelts, as well as the red six-point harness which is fitted on the driver’s side.

A white FIA-homologated roll cage helps to safeguard the driver and passenger, and an Alcantara-wrapped three-spoke Sparco steering wheel is fitted, along with a set of Tilton floor-mounted pedals with adjustable brake bias.

Information is provided via an AIM Mychron XG data logger and digital display, and the door cards, dashboard and transmission tunnel have been custom-fabricated from sheet metal, which is in very good shape – although the seller notes that there are some minor scratches on the trim panels. All of the interior buttons, switches and controls work without fault, thanks largely to the car’s bespoke military-spec wiring harness.

As an ongoing build which began in 2006, this sensational custom performance car has been routinely serviced as other work is carried out, with its most recent maintenance being performed less than 50 miles ago.

As well as it’s Honda S2000-sourced engine and gearbox, the car also features a 4-into-1 manifold, aluminium lightweight flywheel, AEM 1052 ECU, a Torsen differential from a Mazda MX-5 with a custom final drive of 4.7:1, and a fully customised MX-5 rear subframe with tubular wishbones and coilovers. Its front brakes are four-piston Brembo items from a Seat Leon Cupra R with 310mmx28mm floating discs, while Mistubishi Evo VIII Brembo two-piston brakes with 290mmx22mm floating discs are fitted at the rear. The steering rack has been upgraded with a bespoke item, and the chassis has been fully rebuilt with individual suspension, and custom tubular wishbones.

The vendor notes that the car is in very good running order, and the ECU is currently running a base map to pass the TÜV inspection following a conversion from the F1 injector set-up, which was mapped on E85 fuel. Therefore, a remap would be in order to allow it to reach its true performance potential. The wheels are fitted with brand-new Nankang NS2R semi-slick road tyres in 225/45 R16 at the front and Yokohama AD08R track tyres in size 225/50 R16 at the rear.

This heavily-modified Alfa Romeo will be accompanied by a comprehensive array of spare parts and other equipment, including two additional sets of wheels and tyres, a spare gear set for longer final drive, a full underbody aero package including Radical race car diffuser, race hardware and software package, an extra safety harness, a spare HANS-compatible FIA race seat, hydraulic handbrake, brake pads, headlights, ECU and wheel bearings.

This Alfa Romeo GT Junior ‘CLR’ is an incredible one-off lightweight track car, which has been meticulously redesigned and rebuilt by a qualified aeronautical engineer. With both FIA and TÜV approval, it is ready to take on both the road and track, although it truly belongs on the racing circuit at the hands of a skilled driver, who can make the most of its screaming Honda S2000 engine, 874kg kerb weight, and remarkable chassis setup.

To add to the pedigree and history of this car, the original owner from the 1970s has recently been in contact with the current owner, and kindly sent original service and registration documentation along with historic photos which will be included – meaning this extreme development of the classic 105 Series still has a charming connection to its past.

The description of this auction lot is, to the best of the seller's knowledge, accurate and not misleading. Collecting Cars requests a range of detail about the lot from the seller, and performs a level of due diligence. However, bidders must satisfy themselves as to the accuracy of the description, and conduct any research they feel is necessary before committing to a bid. Please see our Terms and Conditions for full details.

As this vehicle is not UK-registered, it cannot be run through Collecting Cars’ standard online HPI check process.