The Gran Sport name has been used on several high-performance cars built by General Motors for its Buick brand since 1965. In the GM brands hierarchy, Buick was surpassed in luxury and comfort appointments only by Cadillac, which did not produce performance models. As a result, the Buick GS series were the most opulently equipped GM sport models of their era.
The Gran Sport performance enhancements on all Buick products during this era sought to affirm Buick's tradition of producing powerful and comfortable products going back to the 1930s when all Buicks of the time were upgraded to the Buick Fireball Straight Eight, then installed the Roadmaster engine in the shortest model Special and introduced the Century, known as "the banker's hot rod" with a three speed synchromesh manual transmission. The Gran Sport sought to identify cars that were fun to drive with a luxury approach.
Skylark based Gran Sports
The 1965 Skylark Gran Sport was the intermediate Buick Skylark with the Gran Sport option added. Although a V8 was already offered in the Skylark, the Gran Sport had the largest engine permitted by GM - a Buick V8 (called a 400 by Buick because that was the maximum engine size allowed in 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, including corporate stablemates Pontiac GTO, Chevrolet Chevelle SS and Oldsmobile 442, when compared to those from the more conservative and luxurious 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.
GS California
Buick touted the California as "The Distinctive Personal Car for Americana on the GO", using the Skylark platform. The merchandising creation of the West Coast's Mickey Garrett, the California GS became one of Buick's entries into what is now often known as a junior musclecar. The intent of these autos were to provide the visual impact of the era's supercars with the low maintenance and price of a more economical car, while maintaining reasonable performance levels. When reviewed with these thoughts in mind the California GS delivered quite nicely. They were fitted with the small block GS drivetrain and the exterior received the full treatment including vinyl top, chrome moulding package, GS emblems, and special California scripts. This marketing approach was also used in Colorado, using the "Colorado" name instead of "California".1969 Buick GS Colorado, www.flickr.comA Brief History of the GS Colorado, Ken's Buick GS Home Page Retrieved 18 June 2017
1967 was the maiden year for the California GS. It was available in California only and was not advertised nationally by Buick. Built on the thin-pillar coupe chassis it came equipped with the 340 ci/260 hp engine and Super Turbine 300 transmission. Bench seats were standard and accessories were kept to a minimum to help keep the price down. Car Life tested one in their June issue and ran the 1/4 in 16.7 seconds at 81 mph, they also recorded a top speed of 105 mph. The article contains a lengthy description of the car and how it performed during testing, it is a must read for anyone interested in learning more about the '67 California GS.
Mid year 1968 saw the official introduction of the California GS, and it is frequently known as a '69 model.Guide to Muscle Cars Magazine, 2/87, p.64. Buick asked "Why settle for less when the California GS, built especially for YOU, costs no more?" Exclusively designed for Golden State motorists, Buick advertised the car nationally as a high performance family sports car at an economy car price. Though the car was not included in Buick's yearly catalog it was shown in a two-page black and white fold out brochure. Custom California GS emblems again graced the rear fenders while GS ornamentation could be found in the grille and sail panels. The drivetrain included Buick's new for '68 350-4 V8 with 10.25:1 compression and Rochester (GM) 4GC Quadrajet four-barrel (four-choke) carburetor,Guide to Muscle Cars Magazine, 2/87, p.62. producing 280 hp and 375 lb·ft of torque. The two-speed Super Turbine 300 transmission (driving a 3.23:1 rear axle gear, designed for highway cruising) and bench seat interior were again the only choices. Buick also added chrome plated wheels and air cleaner lid to the two-door thin pillar coupe. Tires were on rims.
1969 was the last year of production for the California GS. The car was for the first time featured in Buick's big brochure. A two-page color picture of the thin pillar coupe and pictures of the again standard bench seat interior were included along with equipment descriptions. Tom McCahill tested the car and recorded a 0–60 mph time of 9.5 seconds and a top speed of 110 mph. Again the car came with Buick's 280 hp 350-4 engine but now it was mated to the new Turbo 350 transmission. Custom California emblems again graced the rear fenders, and the rear marker lights were plain red without Buick's normal 350 or 400 script. Vinyl tops, as with previous years, were standard fare with the California's distinctive GS logo on the sail panel.
Gran Sport 340/350 In 1967 Buick added a version, there was the GS 340 and the GS California sub-model, little more than the Skylark hardtop with new badging and trim,Flory, J. "Kelly", Jr. American Cars 1960-1972 (Jefferson, NC: McFarland & Coy, 2004), p.484. The 340 produced 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" small-block V8 engine. A California 2-door coupe appeared in 1969;Flory, p.641. 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;Flory, p.718. in addition, 10,148 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.
Gran Sport 400
In 1968 and 1969 Buick offered the GS 400 in a convertible and hardtop model. Standard issue of the GS 400 was a 400 cubic inch (6.6 L) engine (with likely lower stated horsepower rating to keep insurance premiums lower) of 340 horsepower (350 hp stage 1 ) and 440 ft. lbs. torque, a four barrel Rochester Quadrajet carburetor, dual exhaust, 2.93 standard gear ratio optional ( limited slip differential, (3.64 stage 1 option, 3.42 with A/C ), and the available three speed turbo Super Turbine 400 automatic transmission (revered as the finest automatic transmission ever built, and commonly called Turbo 400), U-shape Hurst (automatic transmission) shifter and linkage, located on a center console. A 1968 or 1969 GS400 equipped with the TH400 auto transmission was faster off the line than many of its contemporaries thanks to an unusually "low" 1st gear. Shift pattern for the TH400 from most forward position is Park, Reverse, Neutral, Drive, Second, First. A standard three-speed or optional four-speed manual gearbox was also available. Compression ratio on this engine was a moderately high 10.25:1, which allowed for the use of any grade gasoline to be used in normal driving without pinging. The factory air cleaner was covered with a large round chromed cover, secured with a wing nut. The small air scoop behind the hood hinge-line on the 1968 model was generally fake, although it could be functional if ordered with the very rare ram air package. 1969 brought ram air as standard to the GS.
Like all of the GM versions of this body style in this period, the convertible chassis was considerably more robust than the hardtop version. In fact, the convertible chassis was a full box frame chassis that had numerous lightening holes. The hardtop chassis was a 3/4 box frame with no lightening holes. The only GM hardtop ever built with the "Swiss cheese" convertible chassis was the GTO Judge. Same chassis. All of the GS400 convertibles were built at GM's Fremont, California assembly line.
Gran Sport 455
The 400 was replaced for 1970 with the Buick V8 engine, used in the GS 455. The base model was rated at and at 2800 rpm of torque. In the optional Stage 1 trim equipped with a single 4-barrel Rochester Quadrajet carburetor was rated at SAE gross at 4600 rpm and of torque at 2800 rpm. As with all American engines produced prior to the 1972 model year, these were SAE gross ratings, which are generally significantly higher than SAE net ratings and are not indicative of what actual production engines produce in their "as installed" condition (with all engine accessories and full exhaust system in place). The fastest magazine test results from this period were obtained by MOTOR TREND Magazine, which managed to extract a 13.38 ET at 105.5 mph from their 3,810 pound GS Stage 1 coupe test car. Using Hale's Trap Speed formula, this result indicated actual "as installed" peak HP of approximately 360 SAE Net (ironically the same as its advertised Gross Figure, meaning this engine was very conservatively rated for that time period).
Dennis Manner, Buick Engine development engineer still recalls the production-line pulled engine dyno test results from 1970 where the lowest HP output of the 15 tested 455 Stage 1 engines was roughly 425 hp.
The December 2004 issue of Musclecar Enthusiast magazine conducted an engine dynamometer test of a freshly rebuilt and well documented 1970 455 Stage 1 (bored .040" over to 464 cubic inches and minus the power-robbing factory engine fan, air cleaner assembly and mufflers). In that condition and with factory timing and carburetor tuning, the engine produced a maximum of 360.9 Gross Horsepower. Optimal carburetor and ignition tuning yielded a peak Gross HP reading of 381.7 HP - again with no engine fan, air cleaner or mufflers in place. While urban legend would have us believe that these engines made "420 HP from the factory," actual empirical results prove otherwise. Although another dynamometer test on a 1970 Skylark GS Stage I showed 471 SAE gross hp, which is more consistent with the engine producing about 360 SAE net hp.
The Stage 1 engine option used cylinder heads that, while using raw castings of the same pattern as all of the other Buick 455s sharing the same model year, were machined differently in order to accept larger valves (2.13" intake and 1.755" exhaust), and to produce smaller compression chambers for increased static compression ratio. The option also included a more aggressive camshaft, a specially tuned 4-barrel Quadrajet carburetor, more aggressive ignition timing,5/8 inch oil pickup tube and a higher numerical final drive, and was available with either Turbo Hydra-matic 400 3-speed automatic transmission, or a Muncie M-21 (not m22) 4-speed manual transmission (although it was later discovered, and confirmed, that one 1970 GS Stage 1 convertible was produced with a 3-speed manual and a standard 3.64:1 Positraction axle ratio). Stage 1 cars equipped with air conditioning received a 3.42 axle ratio.