Chevrolet Small-Block engine

The Chevrolet small-block engine is a series of automobile V8 engines built by the Chevrolet Division of General Motors using the same basic small (for a V8) engine block. Retroactively referred to as the "Generation I" small-block, it is distinct from subsequent "Generation II" LT and "Generation III" LS engines.

Production of the original small-block began in 1955 with a displacement of 265 cu in (4.3 L), growing incrementally over time until reaching 400 cu in (6.6 L) in 1970. Several intermediate displacements appeared over the years, such as the 283 cu in (4.6 L) that was available with fuel injection, the 327 cu in (5.4 L) (5.3L), as well as the numerous 350 cu in (5.7 L) versions. Introduced as a performance engine in 1967, the 350 went on to be employed in both high- and low-output variants across the entire Chevrolet product line.

Although all four of Chevrolet's siblings of the period (Buick, Cadillac, Oldsmobile, and Pontiac) designed their own V8s, it was the Chevrolet 350 cu in (5.7 L) small-block that became the GM corporate standard. Over the years, every American General Motors division except Saturn used it and its descendants in their vehicles

Finally superseded by GM's Generation II LT and Generation III LS V8s in the early 2000s and discontinued in 2004, the engine is still made by a GM subsidiary in Mexico as an aftermarket replacement. In all, over 90,000,000 small-blocks have been built in carbureted and fuel injected forms since 1955. The small-block family line was honored as one of the 10 Best Engines of the 20th Century by automotive magazine Ward's AutoWorld.

Confusion with LT and LS engines
The original Chevrolet-designed small-block is a specific family of engines manufactured originally in 1955 and installed as production powerplants by GM for 48 years.

Subsequent GM small block V-8 engine designs built on different blocks are often confused with the original small-block.


 * For more information on the Generation II small-block V8s, which differ mainly in their reverse-flow cooling system, see the GM LT engine.


 * For more information on the current family of Generation III/IV General Motors small-block V8s see the GM LS engine.

Overview
The first generation of Chevrolet small-blocks began with the 1955 Chevrolet 265 cu in (4.3 L) V8 offered in the Corvette and Bel Air. Soon after being introduced, it quickly gained popularity among stock car racers, becoming known as the "Mighty Mouse" motor, after the popular cartoon character of the time.

By 1957 it had grown to 283 cu in (4.6 L). Fitted with the optional Rochester mechanical fuel injection, it became one of the first production engines ever to make one horsepower per cubic inch. The 283 would later be extended to other Chevrolet models, replacing the old style 265 V8s.

high-performance 327 cu in (5.4 L) variant followed, turning out as much as 375 hp and increasing horsepower per cubic inch to 1.15.

It was, however, the 350 cu in (5.7 L) series that came to be the best known Chevrolet small block. The engine's oversquare 4.00-inch bore and 3.48-inch stroke (102 mm by 88 mm) are nearly identical to the 436 hp (325 kW) LS3 engine of today, but much has changed. Installed in everything from station wagons to sports cars, in commercial vehicles, and even in boats and (in highly modified form) airplanes, it is by far the most widely used small-block of all-time.

Though not offered in GM vehicles since 2004, it is still in production today at General Motors' Toluca, Mexico plant under the company's "Mr Goodwrench" brand, and is also manufactured as an industrial and marine engine by GM Powertrain under the Vortec name.

From 1955-74, the small-block engine was known as the "Turbo-Fire V8".

Small Block Chevrolet V8 ( 1955-1998)
The small-block made its debut in 1955 and remained popular for over five decades for its relatively compact size, light weight, and extensive aftermarket support. The engines have been placed into families with the name of each family being the bore size of that family’s progenitor.

3.75 in bore family (1955-1973)
The engine family from which all Chevy V8s from the big blocks to today's LS7 and LS9 evolved is the 265/283 small block family. Of the three engines in this family, two of them, the 265 and the 283, have gone down in automotive history. The first of this family was the 265 in 1955. The 283, famous for being one of the first engines to make 1 hp per cubic inch is also famous for being the evolutionary stepping stone that would give rise to later small blocks and to the “W” blocks which would later give rise to the Chevy big blocks. The last of this family was the 307 which was a stroked 283 with a medium journal.

265
The 265 cu in (4.3 L) V8 was the first Chevrolet small block. Designed by Ed Cole's group at Chevrolet to provide a more powerful engine for the 1955 Corvette than the model's original "stove bolt" in-line six, the 165 hp (123 kW) 2-barrel debut version went from drawings to production in just 15 weeks.

A pushrod cast-iron engine with hydraulic lifters, the small block was available with an optional 4-barrel Rochester carburetor, increasing engine output to 195 hp (145 kW). The oversquare (3.75 in (95 mm) bore, 3 in (76 mm) stroke) engine's 4.4 in (111.8 mm) bore spacing would continue in use for decades.

Also available in the Bel Air sedan, the basic passenger car version produced 162 hp (121 kW) with a 2-barrel carburetor. Upgraded to a four-barrel Rochester, dual exhaust "Power Pack" version, the engine was conservatively rated at 180 hp (134 kW).

A shortcoming of the 1955 265 was that the engine had no provision for oil filtration built into the block, instead relying on an add-on filter mounted on the thermostat housing. In spite of its novel green-sand foundry construction, the '55 block's lack of adequate oil filtration leaves it typically only desirable to period collectors.

The 1956 Corvette introduced three versions of this engine - 210 hp (157 kW) with a single 4-barrel carb, 225 hp (168 kW) with twin 4-barrels, and 240 hp (179 kW) with twin fours and a high-lift cam.

283
The 265 ci V-8 was bored out to 3.875 in (98 mm) in 1957, giving it a 283 cu in (4.6 L) displacement. Five different versions between 185 hp (138 kW) and 283 hp (211 kW) were available, depending on whether a single carb, twin carbs, or fuel injection was used. Power was up a bit each year for 1958, 1959, and 1960. The 1957 Ramjet mechanical fuel injection version produced an even 1 hp (0.746 kW) per cubic inch, an impressive feat at the time. Many tout this as the first US-built production V8 to produce one horsepower per cubic inch.

Besides being available in the Chevrolet line, it was optional in Checker Taxis beginning in 1965.

307
A 307 cu in (5 L) version was produced from 1968 through 1973. Engine bore was 3.875 inches (98.4 mm) with a 3.25-inch (82.6 mm) stroke.

The 307 replaced the 283 (but are the same engine block with a longer stroke) in Chevrolet cars in 1968 and produced 200 hp (149 kW) SAE gross at 4600 rpm and 300 lb·ft (407 N·m) of torque at 2400 rpm in the 1960s. The later emissions-modified versions produced just 115 hp (86 kW) SAE net, giving the engine one of the lowest power-per-displacement ratings of all time. Chevrolet never produced a high-performance version of this engine, though they did produce, for Outboard Marine Corporation, a high-performance marinized 307, rated at 235 hp (175 kW) and 245 hp (183 kW) SAE gross, depending on year, that shipped with the Corvette/Z-28's cast aluminum valve covers and Rochester QuadraJet carb. Chevy also built other versions of the OMC 307 rated at 210 hp (157 kW), 215 hp (160 kW) and 225 hp (168 kW) SAE gross.

4.00 in bore family (1962-1998)
Originally intended as the performance block, this engine family through the 350 CID became an all purpose engine that saw use in many applications from Corvettes to trucks. All engines in this family share the same block dimensions and sometimes even the same casting number; the latter meaning engines were of the same block, but with different strokes (e.g. the casting number 3970010 was used by all three engines: 302, 327, and 350). This engine family was updated in 1968 for the use of 2.45” medium-sized journals. The first engine in this family was the small journal 327 in 1962 and the last being 1992's medium journal 350. The medium journal 350 would later be further developed into the "Generation II" LT 350 in the early 1990’s.

327
The 327 cu in (5.4 L) V8, introduced in 1962, had a bore and stroke of 4 in (102 mm) by 3.25 in. Power ranged from 250 hp (186 kW) L30 to 375 hp (280 kW) depending on the choice of carburetor or fuel injection, camshaft, cylinder heads, pistons and intake manifold. In 1962, the Duntov solid lifter cam versions produced 340 hp (254 kW), 344 lb·ft (466 N·m) with single Carter 4-barrel, and 360 hp (268 kW), 352 lb·ft (477 N·m) with Rochester mechanical fuel injection. In 1964, horsepower increased to 365 hp (272 kW) for the now dubbed L-79 version, and 375 hp (280 kW) for the fuel injected L-84 respectively, making the L-84 the most powerful naturally aspirated, single-cam, production small block V8 until the appearance of the 385 hp (287 kW), 385 lb·ft (522 N·m) Generation III LS6 in 2001. This block is one of three displacements that underwent a major change in 1968/1969 when the main journal size was increased from 2.30 inches (58.4 mm) to 2.45 inches (62.2 mm).

In 1966, Checker began offering the 327 as an option.

350
The 350 first appeared as a high-performance 295 hp L-48 option for the 1967 Chevrolet Camaro. Two years later it was made available in the Nova, and finally in 1969 the balance of the Chevrolet line received the 350. Many variants followed:

Years: 1967-1980
 * L-48

The L-48 is the original 350 cu in (5.7 L), available only in the Camaro or Chevy II/Nova in '67 & '68. In '69 it was used in almost everything; Camaros, Corvettes, Impalas, El Caminos, Chevelles & Novas. From '75-'80 it was available only in the Corvette. L-48's use a Hyd Cam, 4bbl Qjet, Cast pistons, 2 bolt main caps, "Pink" Rods, #0014 Blocks & #993 heads. Power output ranges from 300HP(gross) down to 175HP(net).

The L-48 was the standard engine in the 1971 Chevrolet Corvette. It produced 270 hp and with an 8.5:1 compression ratio.

The 1976-1979 L-48 was the standard Corvette engine and produced 270 hp (201 kW) and 360 lb·ft (488 N·m) with an 8.5:1 compression ratio.

In 1972 the only way to get a L-48 (4bbl V8) in a Chevy Nova was to get the Super Sport Package. This is indicated by the 5th digit in the VIN being a "K". 1972 was the only year you could verify the Super Sport package by the VIN.

In 1973 the "L-48" had cold air induction (throttle activated) and developed 190 hp (142 kW) (net). Beginning in 1974 the hp was reduced for several years until it reached a low of 165 hp (123 kW) (net) in 1975, before rising again.

Years: 1969, 1970, 1972-1975
 * ZQ3

The ZQ3 was the standard engine in the 1969-1970 Chevrolet Corvette. It was a 300 hp (224 kW) version of the 350 cu in (5.7 L) small-block, with 10.25:1 compression and hydraulic lifters. It used a Rochester "4MV" Quadra-Jet 4-barrel carburetor. This was the first block produced that featured the larger 2.45 inch main bearing versus the older 2.30 inch main bearing in 1968/1969.


 * note* post 1971 blocks had a lower nickel content but thicker cylinder deck, and post 1971 heads of the small block chevy used less iron in them and are lighter wight, but less powerfull because of the lower compression ratios used.

The 1972 ZQ3 produced 200 hp (149 kW) and 300 lb·ft (407 N·m) with 8.5:1 compression, dropping another 10 hp (7 kW) in 1973. 1975 saw the ZQ3 at 165 hp (123 kW) and 255 lb·ft (346 N·m).

Years: 1969, 1970
 * L46

The L46 was an optional engine on the 1969-1970 Chevrolet Corvette. It was a 349 hp (260 kW), 380 lb·ft (515 N·m) version of the ZQ3 with higher 11:1 compression.

Years: 1970-1972
 * LT-1

The LT-1 was the ultimate 350 cu in (5.7 L) V8, becoming available in 1970. It used solid lifters, 11:1 compression, a high-performance camshaft, and a Holley four-barrel carburetor on a special aluminum intake to produce 370 hp (276 kW) and 380 lb·ft (515 N·m). It was available on the Corvette and Camaro Z28. Power was down in 1971 to 330 hp (246 kW) and 360 lb·ft (488 N·m) with 9:1 compression, and again in 1972 (the last year of the LT-1, now rated using net, rather than gross, measurement) to 255 hp (190 kW) and 280 lb·ft (380 N·m).

The "LT1" designation was later reused on a Generation II GM engine, the LT1.

Years: 1973-1980
 * L82

The 1973-1974 L82 was a "performance" version of the 350 producing 250 hp (186 kW) and 285 lb·ft (386 N·m) from 9:1 compression. It was down to 205 hp (153 kW) and 255 lb·ft (346 N·m) for 1975. It was the optional engine again in 1976-1977, producing 5 hp (4 kW) more. The 1978 L82 recovered somewhat, producing 220 hp (164 kW) and 260 lb·ft (353 N·m), and then 5 hp (4 kW) and 10 lb·ft (14 N·m) more for 1979. 1980 saw yet another 10 hp (7 kW) and 15 lb·ft (20 N·m).

Years: 1981
 * L81

The L81 was the only 5.7 L (350 cu in) Corvette engine for 1981. It produced 190 hp (142 kW) and 280 lb·ft (380 N·m) from 8.2:1 compression, exactly the same as the 1980 L48, but added computer control spark advance, replacing the vacuum advance.

Years: 1982, 1984
 * L83

The 1982 L83 was again the only Corvette engine (and only available with an automatic transmission) producing 200 hp (149 kW) and 285 lb·ft (386 N·m) from 9:1 compression. This was again the only engine on the new 1984 Vette, at 205 hp (153 kW) and 290 lb·ft (393 N·m). The L83 added Cross-Fire fuel injection (twin throttle-body fuel injection). Since GM did not assign a 1983 model year to production Corvettes, there was also no L83 for 1983.


 * L98
 * For the new Generation IV V8, see GM L98.

Years: 1985-1992

The new 1985 L98 added tuned-port fuel injection "TPI", which produced 230 hp (172 kW) and 330 lb·ft (447 N·m). It was standard on all 1985-1991 Corvettes (rated at 230 hp (172 kW)-250 hp (186 kW) and 330 lb·ft (447 N·m)-350 lb·ft (475 N·m)). Aluminum cylinder heads (Corvette only) were released part way through the 1986 model run and continued through the end of L98 Corvette production in 1992. Optional on 87-92 Chevrolet Camaro & Pontiac Firebird models (rated at 225 hp (168 kW)-245 hp (183 kW) and 330 lb·ft (447 N·m)-345 lb·ft (468 N·m)) 1987 versions had 10 hp (7 kW) and 15 lb·ft (20 N·m) more thanks to 9.5:1 compression and a change to hydraulic roller camshaft. Compression was up again in 1991 to 10:1 but output stayed the same.

The LM1 is the base 5.7 L (350 cu in) with a 4-barrel carburetor (usually with a Rochester Quadrajet) in passenger cars until 1988. Throughout its lifespan, it received either a points, electronic, and/or computer-controlled spark system, to conventional and feedback carburetors.
 * LM1

LM1s were superseded with the LO5 powerplant after 1988.

The LO5 was introduced in 1987 for use in Chevrolet/GMC trucks in both the GMT400 (introduced in April 1987 as 1988 models) and the R/V series trucks such as the K5 Blazer, Suburban, and rounded-era pickups formerly classed as the C/K until 1996 which includes chassis cabs and 4-door crew cabs. Although usage was for trucks, vans, and 9C1-optioned Caprices, the LO5 was also used with the following vehicles:
 * LO5


 * 1992/1993 Buick Roadmaster sedan and station wagon
 * 1990 - 1992 Cadillac Brougham (optional engine)
 * 1993 Cadillac Fleetwood
 * 1992/1993 Chevrolet Caprice Wagon (optional engine)
 * 1993 Chevrolet Caprice LTZ
 * 1992 Oldsmobile Custom Cruiser Wagon (optional engine)

LO5 usage was replaced by the GM LT1 after 1993 in GM B-Bodies until production ceased in 1996.

In mid 1996 the L05 was equipped with Vortec heads used in the 1996 G30.

The L31 replaced the LO5 in 1996 - known as the Vortec 5700. Known as the GEN 1+, this was the final incarnation of the 1955-vintage small block, ending production in 2005 with the last vehicle being a Kodiak/Topkick HD truck. Volvo Penta and Mercury Marine still produces the L31. The "MARINE" intake is a potential upgrade for L31 trucks. Using this "MARINE" intake will allow the use of common types of injectors with various flow rates while still maintaining emission compliance.
 * L31

The GM Goodwrench 350 crate engine comes in several variations. The lowest priced uses the pre-1986 four-bolt casting molds with two dipstick locations; pre-1980 on the driver's side and post-1980 on the passenger's side. This engine was produced in Mexico since 1981 as the Targetmaster 350, and now the GM Goodwrench 350.
 * Goodwrench

302
Chevrolet produced a special 302 cu in (4.9 L) engine for Trans Am racing from 1967-1969. It was the product of placing the 3-inch stroke crankshaft into a 4-inch bore block. The 302 used the same crank as the 265 and the 283. When the journal size increased to the standard medium journal size, the crankshaft for the 302 was specially built of forged steel. This engine was used only in the first-generation Camaro Z28. Conservatively rated at 290 hp (216 kW), actual output was around 375 hp (280 kW). This block is one of 3 displacements that underwent a transformation for the 1968/1969 period when the main bearing size was increased from 2.30 in to 2.45 in.

A letter from G.D. Thompson, Chevrolet Engineering Laboratory, dated June 5, 1967 to D.A. Martens, Engineering Department, subject Z-28 Service Pack Power Breakdown states "engine capable of 448 HP will deliver 432HP in full vehicle dress" .... "as installed data corrected to 100 degree brake and 29.52hg dry barometer yields a maximum of 403.8 HP. This correction more closely represents what is available when installed in a vehicle"    *bhp@7400rpm

400
The only block of this family, 400 cu in (6.6 L) small-block, was introduced in 1970 and produced for 10 years. It was loosely based on the medium journal 350 and had a 4.125-inch (104.8 mm) bore and a 3.75-inch (95.3 mm) stroke. The 400 differed from other small blocks in that the cylinders were siamesed, used a 2.65” large journal, and often times had one more freeze plug on both the left and right sides of the block. Initial output was 265 hp (198 kW) and was only available equipped with a 2-barrel carburetor. In 1974 a 4-barrel version of the 400 was introduced, while the 2-barrel version stopped production in 1975. 1976 was the last year that the 400 was used in a Chevrolet Passenger car, available in both the A-Body and B-Body line. While popular with circle-track racers, the engine was prone to cooling troubles if cylinder heads without steam holes were used. They mostly put out 250 hp stock. Due to the way the block was designed, the 2 bolt main engines were stronger than the 4 bolt versions if properly prepped. The 509 2 bolt main block is the most desirable 400 block.

3.670 in bore family (1975-1998)
Designed and built during the era of the gas embargo and tighter emissions, this engine family was meant as “economy” V8’s. This family through the 305 became an all purpose engine that was intended to have better gas economy than the larger 350 but more power and torque than its then contemporary line of inline 6 cylinders. During the 80’s when GM was streamlining their engine lineups, the 305 rose to prominence as Chevrolet’s “Corporate” engine which meant that this Chevrolet engine would be used in multiple GM brands. Through much of the 80’s the 305 became an alternative to the 350 as the main performance engine in the F body cars and even made an appearance in the Corvette for one year in 1980. The first engine in this family was the medium journal 262 in 1975, and the last being medium journal 305. The medium journal 305 would later on, like its contemporary 350, in the early 1990’s be further developed although with a reduced stroke into the "Generation II" LT L99 263.

262
The 1975-1976 262 was a 262 cu in (4.3 L) 90° pushrod V8 with an iron block and heads. Bore and stroke were 3.67 in (93 mm) by 3.10 in (78.7 mm). Power output for 1975 was 110 hp (82 kW) and 195 lb·ft (264 N·m) at 3600 rpm. The 262 was underpowered and was replaced by the 305 the following year.

This was Chevrolet's second 4.3 L-displacement powerplant; two other Chevrolet engines displaced 4.3 L: the Vortec 4300 (a V6 based on the Chevrolet 350, with two cylinders removed), and a derivative of the GenerationII LT engines known as the L99 (using the 305's 3.736-inch bore, 5.94-inch connecting rods, and a 3-inch crankshaft stroke).

This engine was used in the following cars:
 * 1975-1976 Chevrolet Monza
 * 1975 Chevrolet Nova
 * Early 1977 Pontiac Ventura

305
The 305 5.0L variant of the small-block Chevrolet introduced in 1975 had a displacement of 305 cu in (5 L) with a 3.736-inch (94.90 mm) bore, and 3.4803-inch (88.4 mm) stroke. Many performance enthusiasts have a marked resistance to performance upgrades on the 305 because of the high availability of 350 cu in (5.7 L) engines which have considerably more power potential due to the larger displacement and greater selection of high-flow aftermarket cylinder heads. Most cylinder heads with large valves have bore interference or shrouding issues with the narrow bore of the 305 engine, which reduces intake port flow and thus reduces the ability to make power.

Induction systems for the 305 included carburetors (both 2 and 4-barrel), throttle-body injection (TBI), tuned-port fuel injection (TPI), and sequential fuel injection (GM Vortec).

The 305 was used in the following cars: 1963 GMC trucks
 * 1976-1992 Chevrolet Camaro
 * 1980 Chevrolet Corvette (California only)
 * 1977-1993 Chevrolet Caprice (includes Impala)
 * 1977-1986 Pontiac Parisienne
 * 1976-1979 Chevrolet Monza
 * 1976-1979 Chevrolet Nova (also GM X-body clones after 1976)
 * 1976-1988 Chevrolet Malibu, Chevrolet El Camino, and Chevrolet Monte Carlo
 * 1978-1992 Pontiac Firebird
 * 1978-1980 Oldsmobile Cutlass (US Market only, Canadian market 1978-1987)
 * 1991-1992 Oldsmobile Custom Cruiser
 * 1981-1987 Pontiac Grand Prix
 * 1975-1979 Buick Skylark
 * 1977-2003 Chevrolet/GMC Trucks, SUVs, Vans
 * 1991-1992 Cadillac Brougham
 * 1978-1987 Buick Regal

After 1996, its usage was limited to light trucks and SUVs as the Vortec 5000.

† California Emissions

Years:1976-1980
 * LG3

Dualjet 2 bbl carb version with 8.5:1 compression.

Years: 1980-1987
 * LG4

The LG4 produced 150 hp (112 kW)-170 hp (127 kW) and 240 lb·ft (325 N·m)-250 lb·ft (339 N·m). The addition of a knock sensor for the engine management system in 1985 allowed an increase in compression and a more aggressive spark timing map in the ECM. As a result power increased for the 1985 models to 165 hp (123 kW) from the 150 hp (112 kW) rating in 1984.

Years: 1983-1986
 * L69

The L69 featured a compression ratio of 9.5:1, heads from the LU5 engine and the camshaft from the L83. Additionally the engine came equipped with a dual snorkel air cleaner assembly, aluminum intake manifold, aluminum flywheel and a knock sensor which allowed more aggressive spark timing. This engine produced 190 hp (142 kW) @ 4800 and 240 lb·ft (325 N·m) of torque @ 3200 rpm.

Years: 1981-1986
 * LE9

The LE9 5 L (305 cu in) was a truck/van version that also had a 9.5:1 compression ratio, the LG4 cam and 14022601 casting heads featuring 1.84/1.50" valves and 58 cc chambers. The engine made 165 hp (123 kW) @ 4,000 and 250 lb·ft (339 N·m) @ 2,000 rpm.

Years: 1985-1992
 * LB9

The LB9 was introduced with 215 hp (160 kW) and 275 lb·ft (373 N·m) and varied between 190 hp (142 kW)-230 hp (172 kW) (with 275 lb·ft (373 N·m)-300 lb·ft (407 N·m) of torque) over the years offered.

Years: 1987-95
 * LO3

The LO3 produced 170 hp and 255 lb·ft (346 N·m) of torque; 190 hp at 4,400 rpm and 275 lb·ft (373 N·m) at 2,400 in 1993-1995 GM trucks. This engine used throttle-body fuel injection.

267
The 267 was introduced in 1979 for GM F-Body (Camaro), G-bodies (Chevrolet Monte Carlo, El Camino, and Malibu Classic) and also used on GM B-body cars (Impala and Caprice models). The 267 cu in (4.4 L) had the 350's crankshaft stroke of 3.48" and the smallest bore of any small-block, 3.500 in. The 3.500" bore was also used on the 200 cu in (3.3 L) V6, which was introduced a year earlier. (The 200 was a Chevrolet V6 engine based on the small block with the #3 and #6 cylinders removed).

It was available with a Rochester Dualjet 210 - effectively a Rochester Quadrajet with no rear barrels. After 1980, electronic feedback carburetion was used on the 267.

While similar in displacement to the other 4.3-4.4 L V8 engines produced by General Motors (including the Oldsmobile 260 and Pontiac 265, the small bore 267 shared no parts with the other engines and was phased out after the 1982 model year due to inability to conform to emission standards. Chevrolet vehicles eventually used the 305 cu in (5 L) as its base V8 engine.

Major changes
The original design of the small block remained remarkably unchanged for its production run, which began in 1955 and ended, in passenger vehicles, in 2003. The engine is still being built today for many aftermarket applications, both to replace worn-out older engines and also by many builders as high-performance applications. The principal changes to it over the years include:


 * 1956 - Full flow oil filtration was introduced, using a paper element filter in a canister that was mounted to a feature that was added to the cylinder block casting and machined for this purpose.
 * 1957 - The displacement of the base V8 continued at 265 cubic inches but optional V8s were introduced with 283 cubic inch displacement.
 * 1958 - Bosses for side motor mounts were added to the block casting and utilized for production mounts for this and all future model years. However the features for front motor mounts as used in 1955 - 1957 remained part of the block casting in this and future years.  The 265 cubic inch version of the engine was discontinued.
 * 1962 - The block's cylinder wall casting was revised to allow four inch bores and the 327 cubic inch version of the engine using this bore diameter and increased crankshaft stroke was introduced.
 * 1968 - The main journal diameter was increased to 2.45 in (medium) from 2.30 in (small) and the connecting rod journal diameter was increased to 2.10 in from 2.00 in. This allowed the use of cast iron crankshafts as the previous parts were made of forged steel. The rod bolts were changed from 11/32 in. diameter to 3/8 inch. Additionally, the canister/sock style oil filter was now converted to use spin on filters. The oil fill location was moved from a tube on the front of the intake manifold to a cap on either side valve cover.
 * 1986 - The rear main seal was changed from a 2-piece rubber design to a 1-piece rubber design that used a mounting appliance to hold it in place. This necessitated a change in the flywheel/flexplate bolt pattern as well.
 * 1987 - The valve cover surfaces were changed such that cylinder head mounting lip was raised and the bolt location was moved from 4 bolts on the perimeter, to 4 bolts down the centerline of the valve cover (this design debuted on the Corvette in 1986, and Chevrolet 4.3 L the year before). Also changed were the mounting angles of the center 2 bolts on each side of the intake manifold (from 90 degrees to 73 degrees) and the lifter bosses were increased in height to accept roller lifters. The alloy heads for use in the Corvette still retain the non-angled bolts (center 2 bolts attaching to the intake). Also all carburetors were done away with and replaced by TBI (throttle-body injection) fuel injection that acts some what like a carburetor.
 * 1996 - This was the last change for the Generation I engine, and continued through the end of the production run in 2003; all 1997-2003 Generation I engines were Vortec truck engines. The cylinder heads were redesigned using improved ports and combustion chambers similar to those in the Generation II LT1, resulting in significant power increases. The intake manifold bolt pattern was also changed to four bolts per cylinder head instead of the traditional six.