Buick Engines from Nailhead to Now

When Buick’s overhead-valve inline-eight was replaced by the Nailhead in 1953, the Nailhead became the company’s first pushrod V-8. The engine was named after the little valve covers that sat atop the heads. Vertically placed valves created a nearly hemispherical combustion chamber beneath the valve covers. The Nailhead enjoyed revving due to its substantially over square shape. The combination of a compact design and high torque appealed to early hot rodders in the 1950s.

Although the head design ultimately caused exhaust flow issues, the early Nailhead tinkerers experimented with various fuel and air delivery methods. The Nailhead witnessed it all, from Stromberg’s to four-barrels to triple-twos. Tommy Ivo and his multi-engine dragsters are undoubtedly the most popular Nailhead tuners in the world. Ivo, not happy with a pair of Buick V-8s in his first exhibition runner, rigged his Showboat dragster with four Nailheads.

Buick phased out the Nailhead in 1967 after boosting displacement to 401 and eventually 425 cubic inches. Buick’s foray into the muscle-car era began with the 400 and 430, the Nailhead’s replacements. The two “large block” Buicks featured more conventional dome-shaped heads, but retained the Nailhead’s torque proclivity.

Buick’s Grand Sport (GS) was an outlier as a powerful product from one of General Motors’ mid-tier brands. It has the panache of contemporaneous muscle vehicles such as the Chevelle or Charger, but lacked the outrageousness. Nonetheless, the A-Body Buick sold in significant numbers, and you can occasionally see them at drag strips and car events.

In 1970, Buick completely replaced the 400 and 430 with a 455 cubic-inch V8 that came standard with more than 510 pound-feet of torque. Only the Cadillac 500 was a more powerful torque monster at the time. Grand Sports powered with 455 engines from the early 1970s are exceptionally fast cars, capable of quarter-mile times in the low 13s straight from the dealership.

I’ve always found it fascinating that General Motors had three 455 cubic-inch V8 engines at the time, produced by Buick, Oldsmobile, and Pontiac.

While fans of each marquee would dispute endlessly about which is the finest, all three were discontinued in the late 1970s when General Motors reduced their vehicles and engines to meet changing demands and laws.

1970 was an exciting year for enthusiasts of big block V8 engines. Shortly after relaxing its short-sighted prohibition on stuffing large displacement engines into small to mid-size cars—the very formula that gave birth to the muscle car era in the early 1960s with the Pontiac GTO—it suddenly appeared as though every one of its decisions was churning out massive lumps producing massive heaps of horsepower.

Buick was one of the beneficiaries of GM’s new generosity. As with its corporate twin Oldsmobile, Buick introduced a large block V8 engine in 1967, refining it over the next few years from 400 to 430 cubic inches. Suddenly liberated from the stipulation that this engine be limited to full-size sedans and coupes, the carmaker would burst its most powerful engine to date—the 455—across three times the number of vehicles in 1970.

The introduction of the Buick 455 cubic inch V8 was the finest moment of the brand’s muscle car period, and it spawned more than a few legends that would endure well beyond the brand’s mid-decade twilight.

Buick had been toying with GM’s 400 cubic inch limit for ‘intermediate’ automobiles for several years, producing models such as the Gran Sport 400 mid-sizer with V8 engines that pushed up against the internal limit. Following the introduction of the 430 engine in the full-size Buick Riviera coupe (as well as the huge Electra and Wildcat nameplates), it was only natural to continue improving the engine technology that had supplanted the earlier nailhead in the early 1960s.

By 1970, the big block had been expanded to a monstrous 455 cubic inches, putting smaller cars like the Skylark and the newly independent Gran Sport under severe strain at a time when the entire muscle car movement was on the verge of collapsing.

While Pontiac and Oldsmobile also introduced 455 V8s at the same period, each design was unique, having been developed in-house and sharing no components with other General Motors drive trains. Buick’s entrance into the big block race was noted for its lightweight, thin-walled casting, since the company bored out the cylinders rather than expanding the stroke of the 430 engine.

As a result, practically every component except the pistons could be interchanged between the 430, 400, and 455. Additionally, Buick produced a variety of motor cylinder heads, not all of which were compatible with the smaller displacement large blocks. The base motor produced 350 horsepower and 510 pound-feet of torque, while the ‘Stage 1’ package added larger valves, a higher compression ratio, and a choppier cam to boost output to a stated 360 horsepower .

This huge torque output helped make Stage 1-equipped cars formidable drag strip fighters, and it also delivered a significant boost above the 400 cubic inch motor’s output. The Buick GS Stage 1 was succeeded by the more flamboyantly styled but mechanically identical GSX as the company’s premier straight-line weapon.

With a little more money, buyers could choose for the ‘Stage 2‘ package for the 455, which included forged pistons, a lighter rotating assembly, a different set of heads, a better-flowing header and exhaust system, and an even more aggressive camshaft. Additionally, compression was increased to 11.0:1. Stage 2 was essentially a dealer-installed upgrade, and with an estimated power approaching 500hp, it was primarily aimed at professional drag racers. 

After a single year of splendor, the Buick 455 began to regress. Concerned about the impending rule for lead-free gasoline, GM began reducing engine compression throughout practically its entire lineup, with Buick feeling the pain first.

By 1972, the motor had been downgraded to 250hp, and the GSX had been phased out by 1973.

Buick extended the life of the 455 big block engines by putting it into models such as the Centurion and Regal. None of these larger cars possessed the performance capabilities of the departed Gran Sport, relying instead on the motor’s still formidable torque to compensate for the negative effects of pollution controls and low-quality gasoline, which had become a reality for all American vehicles by the mid-1970s. After 1976, the 455 was permanently dropped from Buick’s lineup.