Extraordinary Engines: Chevrolet Small Block V8

How GM made up for giving rival Ford a 30-year head start on V8 engine development by creating the Chevrolet small block V8, versions of which went on to power more than 115 million vehicles worldwide.

When your brand dominates the biggest motor vehicle market in the world, it would be unthinkable to allow your main competitor to achieve a marketing edge and then let that advantage persist for more than 30 years.

That, however, was the response from General Motors’ Chevrolet Division when faced with the challenge in 1932 of Ford’s ‘flat head’ V8 engine.

Chevrolet simply sat back and did nothing to counter its rival’s two-piston advantage until the mid-1950s, by which time the market was stridently demanding more powerful cars. 

Also significant in General Motors’ thinking must surely have been the desperate need of its new Corvette sports car for an engine that could save the underpowered roadster from oblivion.

Chevrolet’s 265 cubic-inch (4.3-litre) pushrod V8 was announced in late 1954. As expected, it was immediately fitted to 1955 model Corvettes, but also became available on other models in Chevrolet’s passenger car range. 

The 'small block' was first offered in the original C1 Corvette back in 1955 (Image: Chevrolet)

Chevrolet’s V8 initially produced an identical 162bhp (121kW) to Ford’s then-new overhead valve, Y-Block V8. From 1956 the Chevrolet 265 could be fitted with single or dual four-barrel carburettors for extra performance, and from 1957 fuel injection became a $484 option on cars with a base price of $2290.

The engines, once Chevrolet added a 348 cubic-inch ‘big block’ to its range, became known as ‘small block’ or ‘SB’ V8s and endeared themselves to tuners and modifiers. This was due to extensive component compatibility between engines of different eras, with cylinder heads, crankshafts, manifolds and ancillaries from later motors working on the early ones and, in some cases, the reverse as well.

Early 4.3-litre engines combined a 3.75-inch bore and 3.0-inch stroke (95.2 x 76.2mm) but could easily have their bores extended and, with modified crankshafts, deliver a longer stroke. Versions of the 265 cubic-inch engine with dual carburettors and a high-lift camshaft could be tuned to produce a hearty 178kW.   

Small block engines for 1958 reached 4.6-litres or 283 cubic-inches, with fuel-injected cars producing 290bhp (216kW). This gave Corvettes a 200km/h top speed and helped provide acceptable performance to the larger and heavier mainstream Chevrolets. 

Capacity during the 1960s continued to increase, with basic engines displacing 307 cubic-inches or 5.044-litres and performance versions reaching 327 cubic-inches (5.3-litres).

As shown in this graphic from 2015, the evolution of the 'small block' has been constant, while its applications have been varied (Image: Chevrolet)

The engines grew progressively larger until by 1970 a typical Corvette or Camaro was displacing 5.7-litres or 350 cubic-inches. Output during 1971 would reach 245kW but that was the peak before performance declined in the face of reduced compression ratios, lower octane fuels and other emission control measures.

By the late 1970s, 350 cubic-inch small blocks as fitted to Corvettes and Z28 Camaros were pale shadows of their 1960s predecessors. 

Basic 5.7-litre four-barrel V8s fitted to the Z28 had an 8.5:1 compression ratio (down from 10.5:1) and produced 165bhp (123kW) at 4800rpm. Similar power was available in 1986 from a Nissan-engined VL Commodore 3.0-litre.

That situation improved from 1985 when Tuned Port fuel-injection was made available in fourth-generation C4 Corvettes. Power by 1988 reached 171kW and that year saw a six-speed manual gearbox become available, but even the automatics were fast. 

As tested by Car & Driver magazine at the time, a Z51-spec Corvette with the four-speed transmission ran 0-97km/h in 5.6-seconds and covered the standing 400 metres in 14.2-seconds. 

It's easy to see why Chevrolet wanted to heavily market the availability of the small block in anything it was fitted to (Image: Chevrolet)

In 1990 the small block V8 fully unleashed its potential when tuning house Callaway offered its own version of the C4 Corvette with a 5.7-litre fuel-injected engine, twin-turbochargers and 382bhp (285kW) plus 760Nm of torque. 

Callaway Corvettes would hit 97km/h from rest in under 5.0-seconds and run the standing 400 metres in 12.9-seconds on street tyres, according to the well-regarded US enthusiast magazine Car & Driver.

A decade later, Chevrolet and its latest small block V8s were firmly back in the performance game, with LS6 versions of the 5.7-litre engine delivering 287kW without any help from forced induction.

Small blocks would subsequently grow from 5.7- to 6.0-litres and then 6.2-litres, but it was the LS7 version that turned heads and shattered preconceptions.

Using an alloy block and 4.4-inch bore spacing, the LS7 had the same 104.8mm bore as a 400 cubic-inch small block from the 1970s, but extended the engine’s stroke to an almost oversquare 101.6mm.

The forged steel crankshaft used six-bolt bearing caps and the engine when fitted to a Corvette Z06 with an 11:1 compression ratio produced a mighty 377kW at 6300rpm. Torque peaked at 650Nm, but more of that later.  

When Holden abandoned production of its own 5.0-litre V8 in 1997, Chevrolet emerged as the supplier of V8 engines for the locally-developed Commodore (Image: Holden)

Australians have been buying cars with small block V8s since 1960, when 283 cubic-inch engines became the standard in locally assembled Chevrolets and Pontiacs. 

From 1968, when Holden adopted V8 power for its mainstream models, the only V8 engine available was the 307 cubic-inch (5.0-litre) unit. Once the two-door Monaro arrived, capacity became 5.3-litres, with 5.7-litre, 350 cubic-inch versions available in Statesman and Monaro models until imports ceased in 1974. But that was not the end of Australia’s involvement with the small block.

Once Holden abandoned production of its own 5.0-litre V8 in 1997, Chevrolet re-emerged as the supplier of engines to suit local Commodore, Statesman and reborn Monaro models.

Chevrolet’s LS1 V8 was a new engine, slightly smaller than the original 350 but still designated 5.7 litres. It used an aluminium block with six main bearings, fuel-injection and coil packs, but with valves still operated via traditional pushrods.

Most powerful and desirable of the LS1 derivatives was Callaway’s C4B, which produced a mighty 298kW and 549Nm of torque. It was available in VTII and VX versions of the Holden Special Vehicles GTS, also in a limited number of Senators and the Monaro-based HSV GTS300 Coupe.

During the early 21st Century, HSV would also use versions of Chevrolet’s LS1 and LS2 V8s, then later the LSA and LS9 supercharged engines which were fitted in limited numbers to HSV’s final Commodore-based models. Supercharged and rated at 474kW, these were the most powerful production V8s ever fitted to an Australian car.

The 'small block' still sees use even in the mid-engined C8 Corvette sold today (Image: Chevrolet)

None could match the displacement of the LS7, however. It was the largest small block Chevrolet V8 ever made, with 427 cubic-inches (7.0 litres) and producing more power than Big Block engines of the same capacity during the unregulated 1960s. 

This engine would appear locally in the Monaros that won a 24-Hour enduro race at Mount Panorama in 2003 and later in HSV’s short-lived W427 sedan.

High performance small blocks today remain available to buyers of various Chevrolet products, from pickups and police cars to 315km/h Corvettes. 

Even when the Corvette platform switched in 2023 from front to mid-engined, its mechanical heart remained a 6.2-litre, dry-sump, 369kW version of the engine that had seen use for almost 70 years and powered around 115 million cars with Chevrolet, Vauxhall and Holden logos.