BUICK BIG BLOCK
Buick introduced a "big block" V8 in 1967 to replace the largest displacement nailheads. It retained a 4.75 in (120.7 mm) cylinder bore spacing, and was produced in three displacements, 400, 430, and 455, through 1976.
400
The 400-cubic-inch (6.6 L) was produced from 1967-1969. This engine has a bore and a stroke of 4.04 in × 3.9 in (102.6 mm × 99.1 mm). It was the only large V8 engine available for the intermediate-sized A-body Buicks due to the GM cubic inch limit restriction in effect through 1970.[29] Most parts except the pistons interchange with the 430 and 455. This 400 engine had the distributor towards the front of the engine, as opposed to the 401/400 nailhead, which had its near the firewall.[30]
430
1968 Wildcat 430 CID engine
The 430-cubic-inch (7.0 L) was only produced from 1967 until 1969. This engine had a bore and a stroke of 4.1875 in × 3.9 in (106.36 mm × 99.06 mm). The 430 four-barrel engine was rated at 360 hp (268 kW) and 475 lb⋅ft (644 N⋅m) of torque. This engine was used in large B-, C- and E-body Buicks. Most parts except the pistons interchange with the 400 and 455.
Buick 455 V8
455 Stage I engine
The 400-based 455 cu in (7.5 L) was produced from 1970–1976, with a bore x stroke of 4.31 in × 3.9 in (109.5 mm × 99.1 mm). Most parts (except pistons and heads) interchange between the 400 and the 430. The base model was rated at 350 hp (261 kW), while the 455 Stage 1 equipped with a single 4-barrel Rochester Quadrajet carburetor was rated at 360 hp (268 kW) at 4600 rpm.[34][35] The regular 455 produced a rated 510 lb⋅ft (691 N⋅m) of torque at 2,800 rpm, more than any other muscle car engine. The horsepower was somewhat reduced in 1971 mainly due to the reduction in cylinder compression ratio, a change which was mandated by GM in order to cope with the introduction of new federal laws which would require new cars to use low octane gasoline in an effort to reduce exhaust emissions. Then, starting in 1972, the horsepower rating on paper would be reduced again due to a shift from SAE gross to SAE net, down to approximately 250 hp (186 kW). Unleaded gasoline and catalytic converters came into play in 1975 for all US manufactured cars. Tightening emissions controls would cause the engine to drop in power still further, a little at a time, through 1976.
The 455 was one of the first "thin-wall casting" engine blocks at GM, and because of this[36] advance in production technology, it weighs significantly less than other engines of comparable size (for example, 150 lb (68 kg) less than a Chevrolet 454[36] and only 25 lb (11 kg) more than a Chevrolet 350)