Buick GS 455 Stage 1

Stage 1 at a glance

Why Buick built a bigger Gran Sport engine

For 1970 General Motors dropped the 400 cu in limit on its mid-size cars, and Buick moved its new 455 into the Gran Sport. The GS 455 outsold the smaller GS 350 in its first year, with 10,148 two-doors against 9,948. The standard 455 already gave 261 kW (350 hp) and 691 Nm (510 lb-ft), and the Stage 1 package was the step above it for owners who drag raced.

For 1970 the package was built around the larger engine and offered on any GS 455, as a coupé or a convertible, with the three-speed, four-speed or automatic gearbox. It was also the engine of 400 of the 678 GSX cars built that year.

Inside the Stage 1 package

The Stage 1 used the same raw cylinder-head castings as other 1970 Buick 455s, machined for bigger valves and smaller combustion chambers, which raised the compression. The valves grew from 50.8 mm (2.00 in) intake and 41.1 mm (1.62 in) exhaust to 54.1 mm (2.13 in) and 44.6 mm (1.755 in). The rest of the package added parts in every system that mattered for sustained high speed:

Automatic cars got a strengthened Turbo Hydra-Matic 400 with a 2.48:1 first gear, and four-speed cars a larger clutch. One period account gives 348 degrees of exhaust duration instead of 346, so sources differ on this detail.

The 455 also had known limits. Wikipedia lists two-bolt main bearing caps, an oiling system marginal for sustained high revs and thin lifter-valley walls that can crack.

The 510 lb-ft figure and the ten horsepower

The Stage 1 and the standard 455 shared one torque figure, 691 Nm (510 lb-ft) at 2,800 rpm, and their power ratings were only 7 kW (10 hp) apart. Few people believed the gap. Buick engineer Dennis Manner later said that the weakest of 15 Stage 1 engines checked on the production-line dynamometer gave about 425 hp, and the NHRA classed the Stage 1 Skylark at 400 hp for Stock racing before the 1970 Winternationals. Street Muscle notes that no American production engine topped the 510 lb-ft rating until the V10 of the 2003 Dodge Viper.

For 1971 Buick lowered compression across the 455 range for low-lead fuel; the standard engine went from 10:1 to 8.5:1. In 1972 the industry switched to net ratings, which explains most of the drop on paper.

Road tests and drag-strip numbers

Motor Trend's 1970 run of 13.38 seconds at 105.5 mph in a 1,728 kg (3,810 lb) Stage 1 coupé was never matched by another magazine, according to Curbside Classic, and critics called the test car a ringer. Other period tests were slower but consistent:

Car Craft summed up the stock cars in 1985 as low-14 and high-13-second performers straight from the showroom. The 1985 Car Review shootout at Gainesville pitted Richard Lasseter's Stage 1 against Roy Badie's Hemi GTX; the Buick won both runs, helped by a Holley carburettor and an Edelbrock intake that the Hemi did not have.

Stage 2, the GSX and the end

Beyond Stage 1, Buick developed a dealer-installed Stage 2 for the 455, with round-port heads, headers, a racing camshaft, forged high-compression pistons, an Edelbrock B4B intake and a Holley 850 cfm carburettor. The parts were not offered openly until 1972, and only about 75 sets of Stage 2 heads were made before porosity problems and emission rules ended them.

The Stage 1 itself lasted beyond the cars covered here: Wikipedia rates the 1973 Stage 1 at 270 hp net in the Century-based GS, and Buick dropped the Stage 1 and 455 options for 1975. The GSX, with 678, 124 and 44 cars in 1970, 1971 and 1972, was the rare dress-up version of the same drivetrain.

Stage 1 today: what to check

The cylinder heads are the quickest engine check. A Car Craft reference reprinted by TeamBuick lists Stage 1 head casting numbers 1240150 for 1970, 1240146 for 1971 and 1238530 for 1972, and the valves should measure 2.13 and 1.75 in. Original invoices, build sheets, the Protect-O-Plate and an entry in the Stage 1 Registry carry most of a car's value. Convertibles are scarce: Street Muscle cites 232 Stage 1 convertibles for 1970.

Two dated sales show the range: a 1970 Stage 1 four-speed coupé sold for US$110,000 at Barrett-Jackson on 24 October 2020, and a 1970 Stage 1 coupé with a four-speed made US$50,400 at RM Sotheby's Arizona sale in 2020. Rivals with the same idea were the Chevrolet Chevelle SS 454 and the Oldsmobile 4-4-2 W-30. All Gran Sport versions are listed in the Buick catalogue.