Prototypes

As the 250 GTO was heavily derived from the earlier 250 GT Berlinetta SWB, Ferrari engineers constructed two 250 GTO prototypes in 1961 by converting existing chassis of this type.[4][14]

The first prototype, designated in official photos as the 1961 Ferrari 250 GT Le Mans Berlinetta Sperimentale, was constructed from chassis 2643GT, originally a 1961 250 GT SWB. It was built to competition specification, which included a reinforced chassis, a competition gearbox and a Tipo 168/61 3.0 L engine tuned to 300 bhp, equipped with dry sump lubrication and six Weber 38 DCN carburetors. Pininfarina constructed a new lightweight aluminium alloy body for this prototype, which resembled that of the 400 Super America coupe. 2643GT was entered by Scuderia Ferrari in the 1961 24 hours of Le Mans, driven by Fernand Tavano and Giancarlo Baghetti. Although they were running as high as 8th overall, they were forced to retire at 4:45 am on Sunday morning due to engine failure.[16] During the course of the race, Ferrari engineers gathered information about the performance of the car which was used to modify and improve it, including the addition of a rear spoiler. During the Le Mans race, 2643GT suffered from high-speed instability, possibly due to the front end design.[4][14] Following Le Mans, 2643GT returned to the factory, where it was used for more testing. The prototype raced again at the 1962 Daytona Continental 3 hours, where it placed 4th overall and 1st in the GT class driven by Stirling Moss.[4][17] Subsequently, it was sold to N.A.R.T. and a succession of private owners.[4][18]

The second prototype was also constructed from a donor car, although sources disagree on the chassis number and type. Several older sources mention the donor as a 1960 250 GT SWB, chassis 2053GT.[4][14][19] Alternatively, other sources have claimed that a 250 GT Boano (0523GT) or a 1959 250 GT SWB (1791GT) was used as the donor car.[20][21][22][23] This prototype was created entirely by the Ferrari factory's racing department under the oversight of Giotto Bizzarrini, including the bodywork. The original chassis was extensively modified, including relocation of the engine mounts lower and further back in the frame. A competition-specification engine was fitted, including six Weber 38 DCN carburetors. The bodywork seen on the second prototype in period photos was rough, unfinished aluminium. The body's ungainly appearance lead the Ferrari team to nickname it "Il Mostro" (the Monster) and the press to call it "The Anteater". Hammer marks, weld beads and bolted or riveted panels could be seen throughout, evidence of the continual modifications performed during factory testing in 1961. Although the body was crudely formed, it displayed features that would be seen in the production 250 GTO, including the overall profile of a low hood and high rear, triple front air intakes, engine bay cooling slots in the front fenders and plexiglass-covered headlights. The interior was hastily constructed and even more minimal than in the production 250 GTO, with scattered instrumentation and a bare aluminium dashboard.[4][14]

The second prototype was tested at Monza in September 1961 by Stirling Moss. Results were promising, as the prototype was able to lap the circuit faster than a 250 GT SWB. However, the high speed stability issues seen during testing of the first prototype remained. Shortly after this test, construction of the first production 250 GTOs began in late 1961 with chassis 3223GT and 3387GT.[4][14]

As the prototype was no longer needed for testing, the experimental body was scrapped. Regardless of the identity of the chassis, sources are in agreement that the second GTO prototype was either partially or entirely scrapped and is no longer extant in its 1961 form. If 2053GT was indeed the chassis, it was then given a 250 GT SWB style body and sold to Jacques Swaters. 2053GT crashed during the 1962 Nürburgring 1000 km and was then rebodied by Carrozzeria Sports Cars. Subsequently, 2053GT was totally destroyed in an accident at the 1964 Spa 500km.[4][19][14][23]

Variants and related models

Handbuild production, updates, and repairs throughout each car's competition history result in differences both visible and invisible between individual 250 GTOs. Variance in air intake/vent configuration is common among cars. Modifications to the original bodywork were performed by the factory, Scaglietti, or other body shops, usually after crashes or according to a racing team's wishes.[14] In 1964, Ferrari tasked Mauro Forghieri and Mike Parkes with redesigning the 250 GTO's bodywork, resulting in what became known as the GTO '64 (or Series II). Three new cars were produced to the 1964 specification, and four earlier 250 GTOs were retrofitted to it by the factory.[14] This redesign was intended to maintain the GTO's competitiveness for one more year, as the FIA decided to not approve the 250 LM for GT-class racing during the 1964 season. The Ferrari engineers incorporated many of the 250LM's aerodynamic features into the 1964 GTO. This resulted in a visual similarity between the two models, even though the GTO does not share the 250LM's mid engine rear wheel drive layout. The factory also made minor modifications to the engine, gearbox, chassis, suspension and interior. Despite these changes, the overall performance improvement was slight. The GTO '64 still saw some racing success with factory and privateer teams, including an overall win at Daytona in 1964 by Phil Hill and Pedro Rodriguez driving for NART.[24][25][26]

Three 330 GTO specials were made using the 250 GTO chassis and body fitted with 400 Superamerica 4.0-liter motors. Distinguished by a larger bonnet bulge, these cars were used briefly for racing and testing by Scuderia Ferrari before being sold to private customers.[27] Some sources include these cars in the total number of 250 GTOs produced, increasing that number from 36 to 39.

The 330 LMB is sometimes considered a GTO variant.[28] These cars used a 4.0-liter 330 motor and a modified 250 GT Lusso chassis/body. Four were produced in 1963.

Three 275 GTB/C Speciales were built in 1964/65. Despite their origins as competition versions of the 275 GTB, they are sometimes considered developments of the 250 GTO due to similarity of configuration and bodywork.[29][30]

The Ferrari 250 GT SWB Breadvan was a one-off racing car designed for Scuderia Serenissima by Bizzarrini after his departure from Ferrari. It was developed specifically to compete against the then-new 250 GTO. Although based on the earlier 250 GT Berlinetta SWB, the Breadvan provided an opportunity for Bizzarrini to develop the ideas he had first explored with the GTO, such as lower and more aerodynamic bodywork, incorporation of a dry sump, and radical lightening of the entire car.

Homologation

FIA regulations in 1962 required at least one hundred examples of a car to be built in order for it to be homologated for Group 3 Grand Touring Car racing.[33] Ferrari built only 36 250 GTOs (33 of the 1962-design Series I cars and three 1964-design Series II cars, with revised bodywork). The additional three "330 GTO" cars with the four-litre 330 engine —recognizable by the large hump on the bonnet— are sometimes included in the overall production number, bringing the total to 39. It became a popular myth that when FIA inspectors showed up to confirm that 100 examples had been built, Enzo Ferrari shuffled the same cars between different locations, thus giving the impression that the full complement of 100 cars was present.[34] In reality, no deception was required, as the production of the 250 GTO was covered by the homologation of the earlier 250 GT Berlinetta SWB model. These homologation papers were issued in 1960, but extensions were applied for and accepted multiple times between 1961 and 1964, allowing Ferrari to add modifications not covered under the original specification, including changes to the engine, transmission, and suspension.[4] Additionally, since more than 100 bodies had been built according to the earlier 250 GT SWB specification, FIA regulations allowed a new body to be designed, leading to the development of the new 250 GTO body style.[14] This method of homologation was not unique to Ferrari, as similar methods were used to homologate the Aston Martin DB4 GT Zagato and the Jaguar E-Type Lightweight.[4]

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