The Gen I small block came along way from its humble beginnings in 1955.

As we’ve seen in our list so far, it all started with the 265 and then developed into the TPI and LT engines of the 1980s and 90s. But Chevrolet/General Motors really took things to a whole new level with the introduction of its Gen III/IV small block engines in 1996. With a dizzying array of engine sizes and performance levels available, the LS family gave us a number of engines that could’ve qualified for our Top 5 list. The LS1 was a trailblazer and remains an engine swap star. The LS7 was the largest displacement small block ever at 427 cubic inches. And the LS9—well that took small block performance where no one ever thought possible.

For that reason, the LS9 lands in the #1 spot on our list.

Considered a Gen IV small block, the LS9 uses the same 4.4-inch bore spacing of the original small block but takes advantage of the most advanced technologies. Featuring 376 cubic inches of displacement, it’s topped with an Eaton Roots-type supercharger that pushes the power output to 638 horsepower and 604 ft.-lbs. of torque.

It stood as the most powerful factory-installed small block ever until the recent release of the LT4.

It’s no surprise that a work of art like the LS9 is built by hand by a single builder. It starts with an 6.2L aluminum block that is fitted with cast iron cylinder liners. It’s reciprocating assembly is made up of a forged micro-alloy steel crankshaft, titanium steel connecting rods, and forged aluminum pistons with spray oil cooling. It uses high-flow rotocast cylinder heads and a low-overlap camshaft that delivers smooth performance. A dual-pressure/center-feed fuel system adjusts fuel pressure via the engine’s electronic throttle management system, allowing for good idle qualities and sustained high-speed operation at wide-open throttle. The LS9’s advanced electronic throttle control (ETC) provides outstanding throttle response.

The real key to the engine, though, is the Eaton positive displacement 2.3L supercharger with four-lobe rotors. The powerful supercharger is cooled with a specially developed “dual-brick” air-to-liquid intercooler that lowers the incoming air temperature by up to 140 degrees F for even more power production.

In short, this supercharged beast was built to perform—and perform it does.

While the new LT4 begins to build its legacy, the LS9 has been delivering fun and excitement since its debut in the 2009 Chevrolet Corvette ZR1. In testing by Motor Trend magazine, the LS9-powered ZR1 went 0-60 miles-per-hour in 3.3 seconds and finished the quarter-mile in 11.2 seconds. The engine not only delivers massive peak power (we’ll say it again, 638 horsepower), it also offers an incredibly broad torque curve. According to initial testing, the engine made 90 percent of peak torque from 2,600 to 6,000 rpm.

The small block has come a long way since the original 265. With the technological advancements made over 60 years, it’s no surprise that the modern LS9 is our #1 small block of all time.

Top Upgrades

The LS9 makes plenty of power in stock form. But if you’re looking for upgrades, here are some of the most popular items:


The Final List


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Author: David Fuller

David Fuller is OnAllCylinders' managing editor. During his 20-year career in the auto industry, he has covered a variety of races, shows, and industry events and has authored articles for multiple magazines. He has also partnered with mainstream and trade publications on a wide range of editorial projects. In 2012, he helped establish OnAllCylinders, where he enjoys covering all facets of hot rodding and racing.