The SZ's origins lie in a series of one-off specials. In late 1956, Zagato rebodied a crashed Giulietta Sprint Veloce, creating what became known as the SVZ. The result was immediately successful in competition. Zagato went on to build 18 such rebodied Veloces; these SVZ cars were roughly 120 kg lighter than the standard coupé and used the highest-tuned version of the Giulietta engine, producing around 118 PS (87 kW). Their success gave rise to a proper series-production competition model.
The production SZ was premiered at the 1960 Geneva Salon. The body was designed by Ercole Spada at Zagato and constructed entirely in aluminium, with plexiglass side and rear windows to reduce weight. It shared its 1,290 cc twin-cam straight-four with the Sprint Speciale but received twin-choke carburation and a high compression ratio, yielding power in the region of 100 PS (74 kW) in standard competition form. The chassis used Alfa Romeo's proven unibody construction with front wishbone suspension, coil springs, and a located rear solid axle.
Two distinct body styles were produced during the SZ's production run, giving collectors two recognized variants. The original design featured a rounded tail, earning it the Italian nickname Coda Tonda (round tail). The final approximately 30 examples (some sources cite 46) received a longer Kamm-style truncated rear, known as the Coda Tronca, which also incorporated front disc brakes. The Coda Tronca is sometimes referred to informally as the SZ2. In total, 217 examples were built, with the first cars completed in December 1959 and production continuing into 1962. Zagato also rebodied a small number of existing cars with the SZ bodywork, which accounts for minor discrepancies in quoted production figures.
The combination of aluminium bodywork, plexiglass glazing, and a spartan interior made the SZ lighter than virtually any comparable 1.3-litre competitor of the era. This weight advantage, combined with Zagato's aerodynamically refined bodywork, gave the car excellent performance relative to its modest displacement.
The SZ was very successful in racing, both within Italy and at international level. Its primary competitive arena was the GT class for engines up to 1,300 cc, where its power-to-weight ratio proved decisive. On the national Italian scene the SZ accumulated numerous class victories through the early 1960s.
Internationally, the SZ's most significant achievement came in the International Championship for GT Manufacturers, where it helped Alfa Romeo secure the 1.3-litre GT class title in both 1962 and 1963. This was a substantial result for a production-based competition car built in limited numbers by a coachbuilder rather than a dedicated racing department.
An earlier predecessor demonstrated the SZ lineage's potential in rallying when Michel Nicol won the Tour de Corse in 1957 in a related Giulietta-based Zagato. The production SZ continued this tradition of performing well across different competitive formats, from circuit racing to hillclimbs and rallies throughout Europe.
The Giulietta SZ represented the mature expression of a philosophy Alfa Romeo and Zagato had cultivated since the 1950s: lightweight aluminium coachwork over a production-based chassis to create an accessible but genuinely competitive GT car. The car demonstrated that Zagato's skills in aluminium construction and aerodynamic shaping could produce a vehicle that outperformed cars with significantly larger engines in class competition.
The SZ is today regarded as one of the most desirable Giulietta derivatives and a landmark in the history of Italian GT car design. The two body styles — Coda Tonda and Coda Tronca — are both highly sought after, with the Kamm-tailed Coda Tronca particularly valued for its rarity and purposeful appearance. The car's competition record, including back-to-back international championship class victories, confirmed that the SZ was a genuine racing tool rather than merely a styled road car with mild competition use.
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