1978 Buick Regal Sport Coupe (turbo): the production turbo V-6 arrives

For 1978 the Regal was downsized and split off as its own model line, no longer a Century-based trim, and its Sport Coupe introduced Buick's new production turbocharged 3.8-liter V-6, the first year the turbo engine reached regular production Buick showrooms in this form. The turbo engine came with a two-barrel carburetor rated 150 hp or a four-barrel carburetor rated 165 hp, giving buyers two distinct output levels of the same basic turbocharged six from the outset. An Electronic Spark Control knock sensor retarded ignition timing under detonation, a strategy this record's own overview describes as replacing the water injection used on some earlier turbo engines, a comparison this record's own overview makes directly rather than one drawn from separately reading about those earlier engines.^1,2

Turbo Sport Coupe production is given as approximately 30,500, though the exact figure is disputed between two closely related sources: gnttype.org and beforeblack.net's own production page both give 30,507, while beforeblack.net's separate narrative page instead gives 30,508, a one-unit gap this record's own conflict entry carries without resolving in either direction. That total is presented as splitting into 27,811 four-barrel cars and 2,697 two-barrel cars, a pairing the source itself flags as off by one against the 30,507 figure, a discrepancy that happens to be consistent with the 30,508 figure from the same publisher's other page rather than a separate, unrelated error. All 1978 Regal production, across every trim and every engine offered that year, is given as 236,652, meaning the turbo Sport Coupe accounted for roughly one in eight Regals built. A related but separate note states the LeSabre Sport Coupe also used the same turbo V-6 in 1978, at 8,139 units citing Collectible Automobile, and that Buick's own Free Spirit Power Manual gives 40,121 turbo V-6 engines built in total that year across the company's lineup, a company-wide total this record does not attempt to reconcile against the individual model counts given for Regal and LeSabre alone.^3,1

The turbo four-barrel engine is rated 165 hp at 4,000 rpm; its torque figure is disputed between 285 lb-ft at 2,800 rpm from one source and 265 lb-ft at the same 2,800 rpm from another, a 20 lb-ft gap this record's own conflict entry leaves unresolved by carrying the torque field blank in the rating and showing both figures side by side instead of choosing one. The turbo two-barrel engine is rated 150 hp at 3,800 rpm and 245 lb-ft at 2,400 rpm, without a similar dispute attached to either figure. Both turbo engines are documented as available only with a three-speed automatic transmission; this record's own transmission entry states plainly that the turbo V-6 was never offered with a manual gearbox, a claim made about the engine itself rather than scoped specifically to the 1978 model year alone.^1,3

Buick's own 1978 full-line prestige brochure, a marketing document read here from page images, describes the Regal Sport Coupe (model K47) as offering a new turbocharged 3.8 litre (231 CID) V-6 as its standard powerplant. Its Buyer's Guide powerteam chart lists the turbo 2-barrel V-6 (code LC5) as the standard entry and the turbo 4-barrel V-6 (LC8) as available, both with automatic transmission, and it says the 4-barrel would reach California only after January 1, 1978, with every engine's availability contingent on emission certification. The brochure calls the Sport Coupe one of only two turbocharged production cars built in America and prints no horsepower or torque figure for either carburetor, so the ratings in this record still rest on the two enthusiast sources.

The same Buyer's Guide lists what came standard on the Sport Coupe: fast-ratio power steering, power brakes, steel-belted radial P205/70R-14 tires, the Rallye ride-and-handling suspension with front and rear stabilizer bars and firmer springs and shocks, a distinctive domed hood, and a boost light and temperature gage. The brochure's turbocharged V-6 text adds that a specially calibrated automatic transmission and a special rear axle ratio are included. This record carries those as specifications with the brochure's own scope. It also carries the Sport Coupe dimensions as printed in millimetres and inches, including a 108.1 inch wheelbase, a 199.6 inch length, a 72.2 inch width, a 53.4 inch height and a 16.5 cubic foot trunk.

Buick's 1978 exterior color chart gives the Regal fourteen body colors: ten offered on all models (White 11, Silver 15, Black 19, Medium Blue 22, Light Green 44, Tan 61, Dark Gold 63, Saffron 67, Brown 69 and Red 77) and four more (Light Blue 21, Dark Blue 29, Medium Green 45 and Dark Red 79) listed under a special Century, Regal, LeSabre, Estate Wagon, Electra and Riviera group. It also shows Gray and Gold Designers' Accent colors, used with Silver and Tan respectively, and seven extra-cost vinyl top colors. The brochure's Regal interior trim table shows that the Sport Coupe took a cloth or vinyl notchback seat or vinyl buckets as standard, with a 55/45 seat available, but it prints no trim colors or codes. The brochure prints no prices and no option codes, so every option in this record carries a null price and no code except the engine code LC8.

The brochure's Regal Available Equipment list is carried as more than sixty options, from the 4-barrel LC8 engine and heavy-duty cooling, a block heater and the high-altitude package, through the firm ride-and-handling package for trailer towing, automatic level control and a positive-traction differential, to six-way power seating, Cruise-Master, tilt steering, power windows and locks, a range of radios and tape players, air conditioning, wheel and roof options and body-side stripes. Items the brochure lists only for the Regal and Regal Limited, such as power steering, power brakes, automatic transmission and P195 tires, are left out because the Sport Coupe carried them as standard. No published price for the Sport Coupe was read for 1978, and a page that a search summary said quoted one could not be opened, so the prices array stays empty.