Guide: Derivative Wedge - a Historical & Technical Appraisal of the Lancia Stratos Bertone Sibilo
Background
In the period between late 1972 and spring 1978, the Lancia Stratos established itself as the most successful rally car in history.
In Group 4 trim it racked up three World Rally Championship titles, took victory on the 1974 Targa Florio and won the Tour de France five times. Turbocharged Group 5 iterations won the Giro d’Italia in 1974 and 1976.
Despite the fact that Lancia had struggled to sell the 400 road cars required to secure Group 4 homologation, the Stratos had established itself as one of the firm’s most iconic models.
A large part of the Stratos’s appeal was its exciting Bertone bodywork. The memorable design was like no other rally car before or since; it ranked alongside other wedge era luminaries but took on particular significance as one of the few purebred wedge creations that made it to production.
At the Turin Motor Show in April 1978, Bertone unveiled a fully operational design concept conceived as a potential Stratos replacement. Unlike the original though, the new car, dubbed Sibilo, had no pretension as anything other than a machine for street use.
Based on a long wheelbase Stratos chassis, the Sibilo incorporated several innovations to reflect the ever-tightening safety regulations coming into effect. Its name was a reference to the sound made by an object while travelling at speed through the wind.
Bodywork
The Sibilo’s steel bodywork was styled by Bertone’s chief designer, Marcello Gandini.
Gandini had been the architect behind most of Bertone’s famous wedge era creations, most notably the Alfa Romeo Carabo (1968), Lancia Stratos Zero (1970) and Lamborghini Contach (1971). More recently, he had created the Lamborghini Bravo (1974) and Alfa Romeo Navajo (1976), both of which exemplified how changing safety legislation negatively compromised the original wedge ethos.
The need for automobiles to incorporate impact-absorbing panels was now a key consideration. By the mid-to-late 1970s, this trend led to the arrival of innovative bumper-less flexible aprons, a feature pioneered on the Sibilo.
The Sibilo’s seamless design incorporated flush-fitting polycarbonate windows as suitable glass could not be sourced in time. The side windows housed a circular sub-window that popped inwards and slid forwards on rails. An unusual single vertical windscreen wiper ran horizontally from left to right.
The stubby front end was home to retractable headlights and a shallow full width intake. The nose was raked at precisely the same angle as the windscreen.
Squared-off fenders were the only aspect of the design that disturbed the hewn-from-solid appearance. The rear wheels were semi-enclosed.
Air was fed to the engine bay by way of two rectangular intakes carved out from the roof. At the trailing edge of the roof was a discrete lip spoiler.
At the back of the car, the single rectangular light clusters per side were mounted above the tail fascia, either side of a red digital-style Sibilo script. The single-piece rear window lifted up for access to the luggage area.
Bertone opted for a light brown colour scheme with orange pinstripes to highlight the bumper seams.
Interior
Like the exterior, the Sibilo’s dark brown cockpit was also unconventionally styled.
A spoke-less multi-function steering wheel incorporated a speaker, circular buttons for the headlights and indicators and also a row of warning lights. The other controls were located either side of the bulky steering column.
The leading edge of the dash was upholstered in brown leather. The flat top section of the dash was unusually trimmed with brown carpet. Carved into the centre of the dash and angled towards the driver was an array of digital instrumentation.
Padded seat cushions were sunk within the wide side sills and bulky transmission tunnel where Gandini added a futuristic gear lever with a ribbed rubber gaiter. Additional cushions and headrests were attached to the rear bulkhead.
Overall, the cockpit was neither aesthetically pleasing, comfortable, ergonomically styled or easy to see out of.
Chassis
Under the skin was a semi monocoque tubular steel spaceframe as per the original Stratos. However, in order to create a little more space in the cockpit, Bertone added an additional 100mm to the wheelbase (which took it to 2280mm).
In addition to the long wheelbase chassis (numbered S 12201), Bertone added custom wheels shod with Pirelli’s latest generation ultra low profile P7 tyres.
The rest of the specification was pure Stratos.
Partially rose-jointed suspension was via double wishbones at the front and MacPherson struts with lower wishbones at the rear. Adjustable coil springs, telescopic dampers and anti-roll bars were fitted all round.
The 271mm diameter Girling ventilated discs were 22mm thick at the front and 20mm thick at the rear. Twin piston ATE calipers were fitted and there was no servo-assistance.
The twin fuel tanks were mounted either side of the engine up against the rear bulkhead.
Engine / Gearbox
In the engine bay was the usual Ferrari Tipo 236E dual overhead camshaft Dino engine: a 65° V6 with cast iron block and aluminium alloy head. This was mounted transversely in the chassis and displaced 2418cc thanks to a bore and stroke of 92.5mm and 60mm respectively.
The compression ratio was 9.0:1.
Three twin choke Weber 40 IDF 28/29 downdraught carburettors were fitted along with Marelli electronic ignition.
Peak output was 190bhp at 7000rpm and 166lb-ft at 4000rpm.
Transmission was via a Ferrari-supplied five-speed gearbox, single-plate clutch and ZF limited-slip differential.
Weight / Performance
With its long wheelbase chassis and heavy steel body (the original Stratos had a fibreglass body), the Sibilo was most likely a couple of hundred kilograms heavier than the donor (which tipped the scales at 980kg).
Top speed was probably in the region of 135mph. 0-62mph would have required circa seven seconds.
Subsequent History
Soon after it appeared at the Turin Motor Show in April 1978, Bertone repainted the Sibilo a darker shade of brown and changed the wheels from yellow to gold. Lancia badges were also added to the car.
Unfortunately, there was no appetite for a replacement Stratos. From a competition perspective, parent company Fiat went rallying with the 131 Abarth instead and there was simply insufficient demand for a high end Lancia production model such as the Sibilo.
As a result, the Sibilo remained a one off. It was kept by Bertone until the firm’s liquidation sale in 2011.
Text copyright: Supercar Nostalgia
Photo copyright: Bertone - https://www.bertone.it
