Buick Nailhead V8s can be distinguished by the top surfaces of their valve covers being horizontal (parallel to the ground).

)[2] During this era, Buick ranked smoothness above most other marketing objectives, and the Dynaflow transmission's non-shifting design was demonstrably smoother than the other rough shifting automatics then available.

With the Dynaflow, a high torque engine was needed to provide adequate acceleration, so that's what the Nailhead was designed to deliver.

The small-diameter intake runners allowed these engines to develop high torque, with many exceeding 1 ft-lb/cu in (exceptional for the time).

[3] The 264 cu in (4.3 L) produced in 1954 and 1955 was a direct replacement for the 263 straight-eight and the only engine available in Buick's economy "Special" series vehicles.

It was the smallest displacement Nailhead, sharing stroke and deck height with the 322, but having its own smaller bore 3.625 in (92.1 mm).

The larger 322 cu in (5.3 L) was the original Nailhead, used by Buick from 1953 through 1956 in the Roadmaster, Super, and Century models, and the Special in 1956.

The "Fireball" name was dropped after 1957, but the 364 was very briefly called the "B-12000", referring to the 12,000 foot pounds generated by each piston.

The Wildcat 375 was a no-cost option for the 1962-63 LeSabre that used a lower compression ratio to run on lower-octane fuel.

In an effort to overcome the restrictive exhaust-port design of the Nailhead, Buick drag racing enthusiasts in the 1960s adapted superchargers with a custom camshaft to feed intake air in through the exhaust ports; the larger intake ports became the exhaust outlets.

[5] Four-barrel carburetion was standard on the basic 425, called the Wildcat 465 for the torque (as measured in lb-ft) it developed.

The Super Wildcat (Regular Production Option {RPO}-coded Y48) was available on the 1964 Riviera as a factory option (2,122 produced), 1964 Electras (any model, production numbers unknown), 1965 Riviera Gran Sport and 1966 Wildcat GS, which included two four-barrel carburetors and matching intake manifold.

Toward the end of the 1966 model year, around May 1966, Buick offered the Super Wildcat 465 with factory-installed dual four-barrel Carter AFB carburetors as an "MZ" option.

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.

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.

[citation needed] Applications: Buick introduced a "small block" V8 in 1961 with a 4.24 in (107.7 mm) cylinder bore spacing; it was produced in four displacements, 215, 300, 340, and 350.

Originally intended for 180-cubic-inch (2.9 L) displacement, Buick decided on a larger, 215-cubic-inch (3.5 L) size, deemed ideal for the new Y-body cars introduced for 1961, like the Skylark.

Although sharing basic architecture with the Buick, Oldsmobile developed its own all-aluminum 215, the "Rockette V8", to install in its F-85 Cutlass Y-body.

Intended to alleviate a head-warping problem on high-compression versions, Oldsmobile added a sixth head bolt on the intake manifold side.

This meant that the five-bolt Buick heads would fit on Oldsmobile blocks, but not vice versa.

Casting-sealing technology was not advanced enough at that time, and hidden porosity problems caused serious oil leaks, producing an abnormally high scrap ratio.

[26] Rookie driver Dan Gurney qualified eighth and raced well for 92 laps before retiring with transmission problems.

[29] American 215s have also been engine swapped into countless other platforms, especially Chevrolet Vegas[30] and later British cars including the MG RV8 in the 1990s,[31] Triumph TR8, and various sports sedans and sports cars by the MG Rover Group and specialist manufacturers such as TVR.

The engine remains well-supported by enthusiast clubs, specialist parts suppliers, and by shops that specialize in conversions and tuning.

It retained the aluminum cylinder heads, intake manifold, and accessories of the 215 for a dry weight of 405 lb (184 kg).

For 1965, the 300 switched to cast-iron heads, raising dry weight to 467 lb (212 kg), still quite light for a V8 engine of its era.

In 1966, the 300's stroke was increased to 3.85 in (97.8 mm) in a raised block to create the 340, displacing 340.2 cu in (5.6 L; 5,574 cc), as a replacement for the four-barrel-carbureted 300.

The taller deck (raised by 0.5625 in (14.3 mm) compared to the 215/300's) meant the intake manifold was of a new design to bolt to the otherwise interchangeable cylinder heads.

The major differences of the 350 in comparison to other GM V8s are Buick's "deep-skirt" engine block construction, the use of cast iron with increased nickel content, under-square cylinder bore sizing, 3 in (76.2 mm) crankshaft main journals, and 6.385 in (162.2 mm) connecting rods.