Back in 1955, when Bill Haley And His Comets were hitting their stride and “jet set” referred to people who actually flew places, General Motors introduced the Chevrolet small block V8 engine. A marvel of compact design, technical innovation and (relative) fuel efficiency, it didn’t take long for the potent powerplant to end up in everything from milk trucks to race cars.

The little engine that could was heralded with the usual corporate fanfare, but few expected it to be the unmitigated success it became. It transformed Chevrolet, helped drive America’s love affair with performance and became one of the 10 best engines of the 20th century. Fifty-six years later, GM says it is about the crank out its 100 millionth small block Chevrolet engine.

Sort of. Actually, not really.

General Motors will crank out a V8 Chevrolet engine that is a descendant of the engine born in 1955. But it isn’t the same engine at all. Contemporary Chevrolet V8s have little in common with the original small block Chevrolet beyond eight cylinders, a single shared dimension and a pushrod valvetrain. So it’s a faux milestone, heralded during GM’s 100th anniversary. But that in no way detracts from the original’s place in history, because the small block Chevrolet engine remains GM’s Mt. Everest.

The V8 engine was something of an anomaly before World War II, when most automakers offered inline fours, sixes and eights. That changed after the war as consumers demanded more performance and power.

Chevrolet was among the last to the V8 party, offering only a straight-six from 1929 until 1954. It was a fine engine but lacked the oomph consumers, particularly the growing post-war hot rod culture, wanted. GM chief engineer Ed Cole set out to design a powerful, light and affordable V8.

Cole’s answer to that equation was elegantly simple: A compact, efficient 90-degree V8 engine with overhead valves, pushrod valvetrain and 4.4-inch on-center bore spacing. The first engine had a displacement of 265 cubic inches and delivered 195 horsepower. It appeared in the (now) iconic 1955 Chevrolet (pictured).

The engine was revolutionary for its light weight, compact size, general simplicity and remarkable durability, said John Wolkonowicz, an automotive historian and former industry analyst. Although there were some hiccups during the first year or so, GM worked them out and the engine quickly became a hit.

Consumers loved the performance and fuel economy, which was on par with the six-cylinder engine it replaced. Racers and rodders loved its performance and light weight, quickly dubbing it “Mighty Mouse.”

“Until the the small block Chevrolet, the flathead Ford engine was the rodder’s delight,” Wolkonowicz said. “That shifted right away when the small block Chevrolet came out. It was small, it was light and it lasted forever. Hot rodders loved it.”

They still do. Even now, you’ll see the small block Chevrolet and its descendants, the LS and LT engines, almost everywhere, powering almost everything. There are no end to the tricks tuners can use to generate enough torque to move houses and enough horsepower to seriously warp your perspective of time and space.

“The performance of the small block transformed Chevrolet,” Jim Campbell, vice president of GM Performance Vehicles and Motorsports, said in a statement. “The small block made Chevrolet the weapon of choice for grassroots racers on the drag-racing and sports-car tracks across America.”

You’d expect him to say that, of course, but it isn’t hyperbole because it’s true. The ubiquitous engine has appeared in everything from stock car racing (more NASCAR wins than any other engine) to drag racing to endurance racing, not to mention an ungodly number of hot rods built in the past 50 years.

The original small block Chevrolet grew in displacement and output over the years. In 1957, the 283 cubic-inch engine fitted with Rochester fuel injection became the first engine to produce one horsepower per cubic inch. The 350 cubic-inch variant appeared in 1967 and eventually appeared in everything from station wagons to sports cars. It almost certainly is the most popular small block V8 engine of all time.

The first-gen small block engine reached its zenith with the 400 cubic-inch monster in 1970. By that point, the venerable mill was all but bulletproof.

“By the time the engine was truly perfected in 1970, 300,000 miles was the norm for a 350 cubic-inch small block Chevrolet,” Wolkonowicz said. “It was a beautiful, remarkable engine.”

Those with jaundiced eyes might say, “Yeah, yeah. That was then. What does an engine designed half a century ago have to do with getting down the road in the 21st century?”

A lot, actually. The DNA of the small-block Chevrolet can be found in modern GM engines.

General Motors revamped the small block when it introduced the 347 cubic-inch LT engine in 1992 to comply with tightening fuel economy and emissions regulations. The LT featured, among other changes, reverse cooling (in which the coolant flows down through the cylinder heads into the engine block) and an optical distributor mounted at the front of the engine. But it was, at its heart, the same engine Cole designed.

GM went back to the drawing board for the LS engine, which first appeared in the Chevrolet Corvette in 1997. Yes, it’s a V8, but it’s not a small block V8.

“Everything is different,” Wolkonowicz said. “The only thing that’s the same is it’s a 90-degree layout with pushrods and a 4.4-inch on-center bore. Every other part of the engine has been redesigned.”

That doesn’t detract from the significance of the original, or the potential of its descendants. GM has stuck with the general design all these years because it still offers the same benefits: small size, light weight and excellent power.

“As fabulous as the original small block was, the new small block is better in every way,” Wolkonowicz said. “It’s more durable. It’s got more performance. It’s quieter. It’s smoother. It is is capable of better fuel economy and lower emissions. It is simply a much better engine. It is to the 21st century as the original was to the 20th century.”

Photos: General Motors