Chevy (Mouse) Small Block

Small Block
Small Block Chevy

Thus, evolution is clearly beneficial, and the small block Chevy engines that have been blasted out of General Motors engine facilities worldwide are no exception.

With the introduction of the small block engine for the 1955 model year, no engineer could have envisaged where we would be today with 638hp, 376 cubic inch engines capable of 26mpg on the interstate and 11-second quarter-mile times off the showroom floor! However, like with anything, there were failures, growing pains, and a period known as the Smog Era, which was essentially the dark ages of automotive technology. As is customary, GM withstood the storm and saw us through, resulting in the contemporary LS family that exists today.

Today, the small block Chevrolet is one of the industry’s most recognizable icons. From boats and light planes to lakesters and European knock-offs, the SBC is a legend owing to its longevity more than its numbers.


The original 265 can trace its origins back to the Corvette division’s never-satisfied engineers and speed enthusiasts. Ed Cole and Zora Arkus-Duntov gave birth to the plant in a frenzied 15 weeks while searching for a suitable substitute for the “stove bolt” inline-six.

The 265 small block was introduced in the all-new 1955 Chevrolet models, with a choice of 162 or 180 horsepower carburetion and camshaft packages. This engine was a significant step in establishing Chevrolet as a “everyman performer” in the public eye, and it was carried over for 1956. It was an available option on all Chevrolet passenger vehicles and pickup trucks and played a significant part in elevating the Corvette’s prestige.


With its introduction in the final year of the “Tri-Five” era – the 1957 Chevrolet – and as the first Chevrolet engine to use factory fuel injection at the renowned 1 horsepower per cubic inch output, the 283 was an outstanding engine for its day and is regarded a milestone in Chevrolet history. Initially, the 283 was just an over bored 265, but engineers discovered that the walls of the previously-cast block were too thin. A thicker-cast block was required.

In 1957 alone, five variants of the 283 were available, ranging in horsepower from 185hp to 283hp thanks to the availability of a single, twin, or “Fuelie” induction system. Mechanical fuel injection, manufactured by Rochester, emerged as the crème de la crème of the 283 kits. The gasoline injected version of the 283 was also offered as an option on both the passenger car and Corvette lines, making anything powered by this uncommon and unique engine a collector’s item today.


Introduced in 1962 and available on all models from the tiny Chevy II to the flashy Corvette, the high-revving 327 was available in a variety of specifications during the course of its brief existence, ranging from 210 to 375 horsepower.

The highlights include the 365hp L-76 and the 375hp L-84, the latter of which included mechanical fuel injection and remained the manufacturer’s highest horsepower-per-cubic-inch engine (1.146hp/cube) until the arrival of the Gen III LS6 in 2001. The 327 had virtually the same cast iron heads as the 283 but with bigger valves.

302 (DZ)

Only available for three model years and offered only as the standard engine in the 1967–1969 Z/28 Camaro, this “little engine that could” incorporated components from the 283 and 327 engines, having been created especially for the Camaro’s Trans-Am racing participation.

The rationale for the tiny displacement was to comply with the T/A series and SCCA standards, which stated that no car could have a displacement greater than 305 cubic inches. The eventual result of this combination of components would be a factory-professed but undervalued 290hp; however, some argue the true output was closer to 350hp. These engines became synonymous with the first-generation Z/28, and while it was not a 1/4-mile star with times in the low-15s, the high-revving 302 screamed around any road course.

We spoke with Ron Sperry, GM’s Power train Component Design Engineer since 1969, about the legendary 302. “These were developed prior to my time, and the majority of the folks that engineered them had their job cut out for them, as the concept was novel at the time. Depending on the application, the only major distinction between any of these castings was the valve train components and the casting numbers, but they were good units for their period given the technology available.”

350 (L-46, L-48, L-82, LT-1)

The 350 was Chevrolet’s longest-lived small-block engine, powering virtually anything imaginable. It debuted as the 300hp L-48 in the 1967 Camaro and later found its way into all of Chevy’s other models. The 360hp LT-1 model was the crown jewel of this monster. While performance (or what remained of it) dragged along during the mid-’70s to early ’80s, the Corvette made do with an underpowered, but relatively decent for the era, L-82 engine delivering in the area of 200hp depending on the year.

Although the engine was phased out of most uses around the turn of the century, it was nonetheless manufactured in Mexico until 2004, resulting in the production of nearly 90,000,000 Gen 1 small block Chevys. The latest and most powerful (in terms of net numbers) version, named the L98, which we’ve decided to devote an entire section to because it was the only MPFI Gen-1 350 produced.

“I was hired at General Motors in 1969,” Ron explained. By that time, the L-48 had been successfully installed under the hoods of numerous Chevrolet muscle vehicles. What many people are unaware of is that these heads remained relatively unchanged until the mid-1970s, when fuel economy and pollution took precedence over performance.

350 (L98)

Chevrolet’s effort to add much-needed performance into its cars during the 1980s was demonstrated by the aluminum head variant of the L98. While these heads are frequently overlooked by builders today, they have been reborn as the GMPP ZZ4 head and are still available over the counter at any GMPP merchant.

“These were the first factory-produced, purpose-built high-performance heads in a long time,” Ron explained. “The aluminum L98 castings were the culmination of our racing efforts, and it showed when they delivered the much-needed performance to the Corvette and F-cars.”


To maintain horsepower levels while reducing compression ratios, the 400-cubic-inch small blocks came just in time to see the height of classic high-performance in ’70 with 265 gross horsepower, before being phased out following the ’76 model year with 175 net horsepower. It was found in a wide variety of vehicles, ranging from intermediate-sized coupes to full-sized pickup trucks.

Although it was never genuinely a performance engine (since smog-era 350’s of the same generation produced greater power), it became a popular among circle-track and drag racers for a time, most likely due to their abundance and low price.

Despite this, these heads – also known as 882 castings – featured a double heat-riser tube and were prone to breaking due to their high operating temperatures. With the aftermarket now making superior products, we would personally recommend leaving these on the shelf for your next engine build.