Buick GSX

The Gran Sport name has been used on several high-performance muscle cars built by Buick. As Buick was the luxury brand one level below Cadillac, which did not have performance models, Buick GS branded models were the most opulently equipped models from GM during this era.

The 1965 Skylark Gran Sport was the intermediate Buick Skylark with the Gran Sport option added. Although a 300 in³ (4,916 cc) V8 was already offered in the Skylark, the Gran Sport had the largest engine permitted by GM - a 400 cu in (6,555 cc) Buick V8. This engine was actually 401 cu in (6,570 cc), but called a "400" by Buick because that was the maximum engine size limit set by General Motors for the intermediate body cars. This engine produced 325 hp (242 kW) and 445 lb·ft (603 Nm) and was known as the "nailhead" engine. Buick sold more than 15,000 Skylarks with the Gran Sport option that first year, and almost as many the next. It was renamed the GS 400 in 1967, and the Gran Sport became its own model in (about) that same year along with a new "400" engine quite different from the famously reliable but becoming-obsolete nailhead engine design that was first introduced in 1953. Sales fell somewhat in the face of increasingly higher-performance and more popular muscle cars from other marques when compared to those from the more stodgy and expensive Buick. Buick, however, stepped it up a notch when introducing the Stage 1 option in 1969. This limited production (less than 1,500 cars in 1969) version delivered 340 hp (253 kW) and 440 lb·ft (597 Nm).

The name Gran Sport replaced the GS moniker with the 1973 Gran Sport, and was again revived in the late eighties on the FWD Skylark model with various performance options added.

In 1967 Buick added a wewe340 cu in (5,572 cc) version, there was the GS 340 and the GS California sub-model, little more than the Skylark hardtop with new badging and trim, The 340 produced 260 hp (194 kW) and 365 lb·ft (495 Nm), and less than 4,000 cars were sold. It was replaced the next year with the GS 350 and similar GS California; these used Buick's 350 cu in (5,735 cc) small-block engine. A California 2-door coupe appeared in 1969; total GS sales for the year, not counting the new California coupe, were 12,465 (4,933 GS 350s, 7,532 GS 400s). Sales of the GS 350 for 1970 climbed to 9,948; in addition, 10,148 455 cu in (7.5 l) 2-doors were built. The Gran Sport 350 outlived its big brothers, lasting until V8 Gran Sport production stopped in 1975, replaced by the Gran Sport 231.

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