Chevy’s immortal Small-Block V-8
It was simple and brilliant all at once — a new V-8 engine with walls so thin it was lighter than the straight-six it replaced, despite two additional cylinders. The new engine had an oversquare bore-to-stroke ratio, meaning its 3.67-inch bore was larger than its 3.00-inch stroke. Its stamped steel rocker arms were mounted on spherical pivots, and its hydraulic lifters metered plenty of oil to the cylinder heads via hollow pushrods. Its pistons were ultra-light and its cylinder heads were interchangeable with wedge-type chambers. It could rev high and was incredibly reliable.
This all added up to an engine that became a metaphor for a car company and, perhaps, a nation. We’re talking, of course, about the small-block Chevy V-8 introduced in 1955.
It powered much of America for well over three decades in cars, trucks, SUVs and boats. And its descendants are still with us today, driving the seventh-generation Corvette as well as GM’s high-volume pickups and full-size SUVs. On its 60th birthday, with production numbers approaching 100 million, it’s appropriate to look back at what made the small-block Chevy a part of American car culture.
The engine was the brainchild of then-Chevrolet chief engineer Ed Cole, working with a core group that included Al Kolbe, Kai Hansen and Harry Barr. “My dad was the prime mover,” says Dave Cole, chairman emeritus of the Center for Automotive Research in Ann Arbor, Michigan. “They did that engine in less than two years, without electronics or modeling tools. There was such a singular focus on that team.” Cole sold the idea to Chevy management with a slogan: “High performance doesn’t have to mean high price.”
“I remember dad driving a 1953 Chevy prototype with a small-block,” Cole recalls in 100 Years of Chevrolet. “We were up north in Michigan going over 100 mph, and we stopped to get some breakfast. A trooper pulled up in the parking lot and asked, ‘What in the world do you have in that car? I’ve been trying to keep up with you for miles.’ Pretty soon, the whole restaurant was outside looking at that car. My dad loved their reaction and you could see the energy in his eyes.”
Cole’s V-8 became known as the small-block only after Chevrolet introduced a larger 348-cid engine in 1958, which became the big-block and would evolve into the famed 409. The larger engine was nicknamed the “rat” to contrast with the small-block’s nickname, the “mouse,” after the cartoon character “Mighty Mouse.”
Five generations later, all GM small-block V-8s share their basic geometry with the original 265-cid Chevy engine from 1955. And they still offer many advantages over sophisticated multi-cam engines thanks to less weight.
Beyond the Flathead
Overhead-valve V-8s had not been around that long when Chevy brought out this engine. Up until the late 1940s, most higher-production V-8s were flatheads (also known as “side-valves” or “L-heads”), thanks largely to Henry Ford, who introduced the Ford flathead V-8 in 1932.
Ford’s engine was compact, reliable and ran on the low-octane gas available. Chevrolet, meanwhile, stuck with its tried and true “Blue Flame” ohv straight-sixes (“A Six for the Price of a Four”) dating from 1929 — and it outsold Ford regularly. Chevy even gussied it up with Carter side-draft carburetors for the original Corvette.
After World War II, with higher-octane fuels available, American auto manufacturers gravitated toward overhead-valve V-8s for more horsepower and efficiency. Zora Arkus-Duntov, who would later become synonymous with the Corvette, created the Ardun overhead-valve conversion kit for the Ford flathead in 1946. It featured hemispherical combustion chambers. It was not a commercial success, however, as Oldsmobile and Cadillac introduced more reliable ohv V-8s in 1949. Chrysler followed up in 1950 with its own hemispherical combustion chamber ohv engine, known as the “Hemi.” Ford entered the fray in 1954, followed by Chevy in 1955.
The small-block represented Chevy’s first V-8 engine since its one-year experiment in 1918. It not only gave Chevrolet a whole new image, but it also helped ensure the survival of the Corvette.
And the small-block was flexible enough to expand, primarily by increasing bore and stroke from its original 265 cid to 283, 327, 350, 400 and all the way up to 427.
What made the Chevy small-block so good? “I think that the small-block V-8 had the right basic foundation,” says Bill Nichols of GM Powertrain. “It had to be small, it had to be lightweight, it had to breathe well, and it had to be easy to use and service.”
Nichols also cites a multi-use strategy: “A whole spectrum of applications was planned, from automotive to marine, and even as a crate engine for hot rodders.”
Besides its lightness and flexibility, one of its secrets was its strength. Former GM engineer and Chevrolet race car collector Bill Tower relates that the original block, despite its thin walls, was particularly strong where the cylinder head bolted up to the block. The engine also oiled well, with the oil system doing its job even at higher rpm — an Achilles heel for many competitive engines, including the Ford V-8.
One of the primary technical breakthroughs in the early days of the small-block was the Duntov camshaft. The basic configuration came from the Ardun engine that Duntov had developed for the flathead Ford V-8. But it translated surprisingly well to the small-block, propelling Duntov to a 150-mph speed record in a Corvette on Daytona Beach in January 1956.
“Duntov had the ability to test with Chevy dyno cells to try different options with timing or camshafts and the like,” says Nichols. “He said, ‘Okay, I can open the valve with valve springs that are this strong such that they won’t fail at a high rpm, and I can get more charge into the cylinder to get more power after the firing of the plug. And I can exhaust it such that I don’t have too much back pressure in the chamber when it fires.’”
Duntov also worked with outside engine builders like the legendary Smokey Yunick and West Coast cam magician Ed Iskenderian. Yunick had an intuitive understanding of engines from racing in NASCAR and preparing the Corvette motors for Sebring in 1956. Iskenderian also had a huge reputation from working on high-performance engines for Ford and Chevy.
“Smokey Yunick was the professor of the small-block,” says Tower. “He saved GM millions. He found out by racing what was weak and what wasn’t.”
Under the influence of people like Yunick, Iskenderian, Duntov and racing director Vince Piggins, the Chevy small-block would become the most successful production-based racing V-8 ever, winning thousands of races in SCCA, NASCAR, Trans Am and even IndyCar over the decades.
Yunick also worked with Zora Arkus-Duntov and John Dolza from Rochester Products on mechanical fuel injection, which debuted with the 283-cid V-8 in 1957. It was the second American engine to claim one horsepower per cubic inch; a limited-production 1956 Chrysler Hemi had beaten GM to the punch.
Tower recalls working with Yunick on exotic combinations, too, like porcelain cylinder walls and nickel alloy blocks. "I worked on the rings and the bores. We started to figure it out, but it was just too expensive to add porcelain at the foundry. But we did use nickel in our racing blocks."
Over time, the small-block evolved into a more sophisticated engine. The second generation debuted with the LT1 in 1992, with higher compression and computerized ignition. The third generation debuted with the LS1 in the fifth-generation Corvette in 1997 and featured an all-aluminum block and oil pan. The fourth-generation in 2005 brought us the 7.0-liter LS7 in the Corvette Z06, which offered the magic number of 427 cubic inches and featured an eight-quart dry-sump oil system as well as titanium valves and connecting rods. The LS9 in the 2009 Corvette ZR1 was supercharged to put out 638 horsepower, while active fuel management also debuted in the fourth-generation small-block for truck and SUV use. The current fifth-generation V-8 added active fuel management to the Corvette as well as direct injection and variable valve timing.
“We’ve improved materials over the years and executed them wisely to be able to take mass out of the engine,” says Nichols. “More recently, we’ve added sodium-filled valve stems for higher revving capability. Valve springs are made of a high-tensile-strength steel alloy for improved fatigue strength and reduced load loss. Even though we expanded out to 7.0 liters with the LS7, we can still maintain a compact design.”
As a testament to its staying power, in 2000, the Chevrolet small-block V-8 was honored by Wards Auto as one of the 10 Best Engines of the 20th Century. And given the beauty of its fundamental design, it appears to have a bright and viable future. It will forever be a legacy of the ingenuity of its father, Ed Cole.