Today, the Corvette is most often categorized as one of America’s most prized performance cars. However, this was not always the case. Prior to the days of GM’s domination of the small-block market, or even the big-block beasts of the 1960s, the Corvette was offered with only one available engine, the Stovebolt inline-six-cylinder.
Often referred to as the “The Blue-Flame”, the Stovebolt-Six’s performance characteristics were anything but “fiery”. Quite the contrary, the Corvette, in its earliest form, was often ridiculed for being underpowered, in comparison to many comparable European sports cars of the era. Nonetheless, the Blue-Flame Stovebolt-Six served as the Genesis of Corvette power, if only for a brief period of time.
Stovebolt Inline 6 Cylinder History
While the 1953-1955 Stovebolt Inline 6-cylinder has been the butt of its fair share of jokes, the engine’s history is more accurately depicted when viewed from the standpoint of top GM brass during the era in which it was unveiled.
During the time, talk had already begun to surface surrounding the potential development of a V8 powerplant that would be viable for production. However, by 1953, this pet-project had amounted to little more than speculation, and little true progress had been made.
Meanwhile, the Corvette-prototype was coming fresh off of a warm reception at the 1953 Motorama. Always the opportunist, Harley Earl, along with others on the forefront of GM design, set out to capitalize on the wave of popularity that surrounded the EX-122 prototype.
The Corvette was greenlighted for fast-tracked production, leaving many design decisions to be made in haste. GM’s upcoming 265 cubic-inch small-block was far from reaching production viability, leaving little option but to adapt Chevrolet’s already popular Stovebolt-Six for use underneath the Corvette’s hood.
At the time, the Stovebolt-Six had already proven quite reliable and had served as the powerplant of choice for many Chevrolet models, dating back to 1929. In reality, the Stovebolt-Six first served as the motivator behind early Chevrolet pickups, during which time the engine was often cited as a workhorse of sorts.
Later sedan-based variants of this engine came to be known as the Powerglide-Six and featured a hydraulic camshaft, wedge-shaped combustion chambers, and a single-barrel downdraft carburetor. In its Powerglide form, the Stovebolt-Six produced 115 horsepower and operated on a 7.5:1 compression ratio.
This more robust version of this engine was further modified, in preparation for fitment beneath the Corvette’s hood. This revised Stovebolt-Six would carry GM’s “Blue-Flame” designation, and serve as the single available engine option for the Chevrolet Corvette between 1953 and 1954.
Stovebolt Inline 6 Cylinder Specifications and Technical Configurations
The Blue-Flame Stovebolt-Six featured a cast-iron engine block, which housed a dropped-forged steel crankshaft. The Blue-Flame’s crankshaft utilized four main-bearings and was of a four-bolt main construction.
Attached to the Stovebolt-Six’s connecting rods was a set of aluminum pistons, which reciprocated within 3.5625” cylinder bores while displaying a stroke of 3.9375”. The Blue-Flame powerplant utilized by the Corvette also carried a higher compression ratio of 8.0:1, than that of prior iterations of the Stovebolt-Six.
When preparing the Stovebolt-Six for use in the Corvette, solid lifters were sourced from the manufacturer’s earlier 261CI truck engine. These lifters were actuated by a redesigned, higher-lift camshaft. This camshaft featured lift values of 0.405” (intake) and 0.414 (exhaust).
The Blue Flame’s block was topped with a single cast-iron cylinder head, which featured dual valve springs, in a bid to prevent valve-float under periods of high-RPM operation. The 235.5 cubic-inch inline-six engine’s head featured valves that measured 1.52” (intake) and 1.29” (exhaust), respectively.
Affixed to the Stovebolt-Six’s head, was a specialty aluminum intake manifold, which served as the point of mount for three Carter single-barrel carburetors, arranged in a horizontal configuration.
All things considered, the Stovebolt-Six produced 150 horsepower and propelled the C1 Corvette to a top speed of 108 MPH. While these figures might seem mundane by today’s standards, the Stovebolt Six’s output was relatively impressive during the horsepower-deprived 1950s.
Stovebolt Inline 6 Cylinder Specs Index
Horsepower: 150 hp @ 4,200 rpm
Compression Ratio: 8.0:1
Displacement: 235CI (3.9L)
Cylinder Bore: 3.562” (90.5 mm)
Stroke: 3.93” (100 mm)
Stovebolt Inline 6 Cylinder Additional Uses
As previously mentioned, the Corvette’s Blue-Flame was an adaptation of GM’s already popular Stovebolt-Six engine platform. The Stovebolt-Six, in various forms, served as the motivator of numerous GM models, beginning in 1929.
Although the Blue-Flame was relegated to base model status within the Corvette lineup by 1955, the Stovebolt-Six persevered well into the future. The famed engine remained a mainstay of Chevrolet production until the 1970s, before U.S-based production ceased. However, the Stovebolt-Six saw continued use in foreign markets, until 2001.
The Little Engine That Could
For many performance buffs, the Blue-Flame Stovebolt-Six seems unworthy of a parting glance. However, to the avid automotive historian, the original Corvette powerplant’s story is one worth being told.
Though outgunned by every Corvette engine that was produced thereafter, the Stovebolt-Six served as the best available engine option for the fledgling sports car, which we all now cherish. Without the Stovebolt-Six, the Corvette might not have ever reached production. For its part, this fact alone places significant value on the story of the little Stovebolt engine that could.