Chevrolet small-block engine

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Chevrolet small-block engine
Manufacturer General Motors
Also called Chevrolet TurboFire
Production 1955–2003
Combustion chamber

262 CID (1975-1976) V8


265 CID (1955-1957) V8


267 CID (1979-1982) V8


283 CID (1957-1967) V8


302 CID (1967-1969) V8


305 CID (1976-2002) V8


307 CID (1968-1973) V8


327 CID (1962-1969) V8


350 CID (1967-2003) V8


400 CID (1970-1981) V8

Cylinder bore 3.670 in (93.2 mm)
3.736 in (94.9 mm)
3.750 in (95.3 mm)
3.875 in (98.4 mm)
4.00 in (101.6 mm)
4.125 in (104.8 mm)
Piston stroke 3.00 in (76.2 mm)
3.10 in (78.7 mm)
3.25 in (82.6 mm)
3.48 in (88.4 mm)
3.75 in (95.3 mm)
Valvetrain OHV
Successor Generation II GM small-block Gen III-V GM 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 US V8 of the time) engine block. Retroactively referred to as the "Generation I" small-block, it is distinct from subsequent "Generation II" LT and "Generation III/IV" LS, and "Generation V" (LT/EcoTec3) engines. Engineer Ed Cole, who would later become GM President, is credited with leading the design for this engine.

Production of the original small-block began in the fall of 1954 for the 1955 model year with a displacement of 265 cu in (4.3 L), growing incrementally over time to 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 mechanical fuel injection, the 327 cu in (5.4 L), 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 of Chevrolet's siblings of the period (Buick, Cadillac, Oldsmobile, Pontiac and Holden) 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Finally superseded by GM's Generation II LT and Generation III LS V8s in the 1990s and discontinued in 2003, the engine is still made by a GM subsidiary in Mexico as a crate engine for replacement and hot rodding purposes. In all, over 100,000,000 small-blocks (as of November 29, 2011) have been built in carbureted and fuel injected forms since 1955. In many respects, the later Generation II and Generation III engines still in production today for various vehicles still trace some of their design lineage to the "small block" design concept first laid down by Ed Cole and his team.

The small-block family line was honored as one of the 10 Best Engines of the 20th Century by automotive magazine Ward's AutoWorld.[1]


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, with the simpler "Mouse" becoming much more common as time went on.

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

A 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. 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 2003, the 350 cu in (5.7 L) series 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 to 1974, the small-block engine was known as the "Turbo-Fire V8".

3.875 in. bore family (1955–1973)[edit]

All Chevrolet's V8s, from the big blocks to today's LS7 and LS9, evolved from 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, introduced in 1955. The 265 had a 3.75 bore. The stroke of the 265 was 3.00, like the 283. 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 later give rise to small blocks and to the "W" blocks, ultimately culminating in the Chevrolet big blocks. The last of this family was the 307, which was a stroked 283 with a medium journal.


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 "stovebolt" in-line six, the 165 hp (123 kW)[2] 2-barrel debut version went from drawings to production in just 15 weeks.[citation needed]

Cole's design borrowed the valve train design being used in the Pontiac V-8 for 1955. The stud mounted independent ball rocker arm designed was patented by Pontiac engineer Clayton Leach for Pontiac's new V-8 in 1948.[clarification needed] by forcing Pontiac division to share its valve train design in the new 1955 Chevrolet V-8.[citation needed]

A pushrod engine with hydraulic lifters, the small block was available with an optional four-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 (110 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 two-barrel carburetor. Upgraded to a four-barrel Rochester, dual exhaust "Power Pack" version, the engine was conservatively rated at 180 hp (134 kW).[citation needed]

A shortcoming of the 1955 265 was its lack of any provision for oil filtration built into the block, instead relying on an add-on filter mounted on the thermostat housing, and that was an "option only". 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 carburetor, 225 hp (168 kW) with twin 4-barrels, and 240 hp (179 kW) with two four-barrel carburetors and a high-lift camshaft.


The 265 ci V-8 was bored out to 3.875 in (98.4 mm) in 1957, giving it a 283 cu in (4,638 cc) displacement. The first 283 motors used the stock 265 blocks. However, the overbore to these blocks resulted in thin cylinder walls. Future 283 blocks were recast to accept the 3.875 bore. 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. Fuel injection yielded the most power topping out at 315 HP in 1961. Horse power was up a bit each year for 1958, 1959, and 1960. The 1957 Ramjet mechanical fuel injection version produced an even 1 hp per cubic inch (61 hp/L), an impressive feat at the time. This was the third U.S.-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.[3] A version of it that was built by GM Canada was also available in Studebakers produced in Canada for 1965 & 1966.


A 307 cu in (5,025 cc) 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. All 307s had large 2.45" journals - the crankshaft is sourced from the 327. Pistons used with the 307 share the same pin height as the 327 but retaining the 283's bore size (prior to 1968 it was possible to stroke a 283 into a 307 where aftermarket pistons had to be used). This engine was also used by Holden in Australia and by General Motors' South African arm.[4] This engine shares many of its dimensions with the 230 inline-six and with the 153 four-cylinder.

4.00 in bore family (1962–1998)[edit]

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 vans. 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 2000's medium journal 350 in pickup trucks and commercial vehicles. The medium journal 350 was further developed into the "Generation II" LT1/4 350 in the early 1990s.


In 1966, General Motors designed a special 302 cu in engine for the production Z/28 Camaro in order for it to meet the Sports Car Club of America (SCCA) Trans-Am Series road racing rules limiting engine displacement to 305 cu in from 1967 to 1969. It was the product of placing the 283 cu in 3.00 in. stroke crankshaft into a 4.00 bore 327 cylinder-block. The 1967 302 used the same nodular cast-iron crankshaft as the 283, with a forged-steel crank that was also produced. This block is one of three displacements, 302/327/350, that underwent a crankshaft bearing diameter transformation for 1968 when the rod-journal size was increased from the 2.00 in. diameter small-journal to a 2.10 large-journal and the main-journal size was increased from 2.30 in. to 2.45. The large-journal connecting rods were thicker (heavier) and used 3/8 in. diameter cap-bolts to replace the small-journal's 11/32. 1968 blocks were made in 2-bolt and 4-bolt versions with the 4-bolt center-three main caps each fastened by two additional bolts which were supported by the addition of heavier crankcase main-web bulkheads. When the journal size increased to the standard large-journal size, the crankshaft for the 302 was specially built of tufftride-hardened forged 1053-steel and fitted with a high-rpm 8.00 in. diameter harmonic balancer. It had a 3/4-length semi-circular windage tray, heat-treated, magnafluxed, shot-peened forged 1038-steel 'pink' connecting rods, floating-pin in `69, forged-aluminum pistons with higher scuff-resistance and better sealing single-moly rings. Its solid-lifter cam, known as the '30-30 Duntov' cam named after its .030/.030 in. hot intake/exhaust valve-lash and Zora Arkus-Duntov (the first Duntov cam was the .012/.018 1957 grind known as the '097, which referred to the last three digits of the casting number) the "Father of the Corvette", was also used in the 1964-65 carbureted 327/365 and F.I. 327/375 engines. It used the '202' 2.02/1.60 valve diameter high-performance 327 double-hump `461 heads, pushrod guide plates, hardened 'blue-stripe' pushrods, edge-orifice lifters to keep more valvetrain oil in the crankcase for high-rpm lubrication, and stiffer valvesprings. In 1967, a new design high-rise cast-aluminum dual-plane intake manifold with larger smoother turn runners was introduced for the Z/28 that the LT-1 350 1969 Corvette and 1970 Z/28 engines were equipped with until the Q-jet carburetor returned in 1973. Unlike the Corvette, the exhaust manifolds were the more restrictive rear outlet 'log' design to clear the Camaro chassis's front cross-member. It had a chrome oil filler tube in the front of the intake manifold next to the thermostat housing from 1967 to 1968, and the first year unique chrome valve covers that had Chevrolet stamped into them without an engine displacement decal pad. In 1968 the engine had the chrome covers, but without the Chevrolet name, that had air cleaner breather and PCV valve grommets. In 1968, a chrome 14.00 x 3.00 in. drop-base open-element air cleaner assembly on a 780cfm vacuum secondary Holley 4-Bbl carburetor. A 'divorced' exhaust crossover port heated well-choke thermostat coil was used to provide cleaner and faster engine warm-up. Its single-point distributor had an ignition point cam designed to reduce point bounce at high rpm along with a vacuum diaphragm to advance ignition timing at idle and part-throttle for economy and emissions. Pulleys for the balancer, alternator, water-pump, as well as optional power-steering, were deep-groove to retain the drive belt(s) at high rpm. In 1969, the 302 shared the finned cast-aluminum valve covers with the LT-1 350 Corvette engine. Conservatively rated at 290 hp (216 kW) (SAE gross) at 5800 rpm and 290 lb-ft at 4800, actual output with its production 11:1 compression ratio was around 376 hp (280 kW) with 1.625 in. primary x 3.00 secondary tubular headers that came in the trunk when ordered with a 1967 Z/28, and associated carburetor main jet and ignition timing tuning[citation needed]. In 1968, the last year for factory headers, they had 1.750 in. primaries x 3.00 secondaries. A stock 1968 Z/28 with the close-ratio transmission, optional transistorized-ignition and 4.88 gear, fitted with little more than the factory plenum cowl cold-air hood induction and headers, was capable of running 12.9 second/108 mph 1/4-mile times on street tires.

After the 1967 Trans-Am campaign with the 4-Bbl induction system producing more horsepower than the competing auto makers' 8-Bbl systems, for 1968 Chevrolet developed a factory 'cross-ram' aluminum intake-manifold package using two Holley 600cfm mechanical secondary carburetors for Trans-Am racing. It was available only as off-road service parts purchased over the Chevrolet dealership parts counter. With the Chevrolet '140 1st-design off-road cam, the package increased a stock 302's hp from 360 hp to approximately 400. Chevrolet went so far as to carry the positive crankcase ventilation (PCV) system over to the cross-ram induction system to retain emissions compliance mandated for U.S.-produced cars beginning in 1967, that also provided full-throttle crankcase pressure venting to the intake air to burn its vapors. Engines prepared for competition use were capable of producing 465 hp with little more than the 8-Bbl induction, ported heads with higher pressure valvesprings, roller rocker arms, and the '754 2nd-design road-race cam. 1967/1968 models' cowl-induction system had an enclosed air-cleaner assembly ducted from its passenger side into the firewall cowl above the heater core. In 1969, factory ZL-2 cowl-induction hoods were available for both the single and dual four-barrel induction systems that were sealed to the air cleaner base ensuring dense cooler, high-pressure, air from the center of the base of the windshield was supplied to the engine for combustion smoothness and maximum power production. Another popular service-parts-only component used on the 302 was the magnetic-pulse Delco transistor-ignition ball-bearing distributor. Introduced in 1967 and also used in the L88 427 Corvette, it eliminated the production breaker-point ignition allowing greater spark energy and more stable ignition timing at all engine speeds including idle. This was one of the least talked about yet most transformative and comprehensive upgrades of its time. Many of the 302's off-road service parts were the development work of racers like Roger Penske. Every part in a SCCA Trans-Am engine had to be available through local Chevrolet parts departments to encourage their use by anyone who wanted them.

While the 302 became a strong Limited Sportsman oval track racing engine in the hands of Bud Lunsford in his 1966 Chevy II, its bore/stroke and rod/stroke geometries made it a natural high-rpm road-racing engine and were responsible for its being among the more reliable production street engines homologated for full competition across all the American makes, winning back-to-back Trans-Am Championships at the hands of Mark Donohue in 1968 and 1969. However, with engines built by Al Bartz, Falconer & Dunn and Traco Engineering, the pinnacle of the 302's use in professional racing was its being the primary engine that powered the outstanding but overshadowed 1968-1976 Formula 5000 Championship Series, a SCCA Formula A open-wheel class designed for lower cost. The engine was also popular in Formula 5000 racing around the world, especially in Australia and New Zealand where it proved slightly more powerful than the Repco-Holden V8. Weighing 1350 lbs., with a 525-550 hp iron block and head engine positioned near the car's polar moment for responsive turn pivoting, a Hewland 5-spd. magnesium transaxle, and 10 in. wide 13 in. front/20 in. wide 15 in. rear magnesium wheels, it produced incredibly exciting racing. They ran 0-60 mph in 2.8 seconds and over 180 mph. Reminiscing about the series, mid-70's Australian F5000 driver Bruce Allison said, “We never used first gear at the start. We started in second, and even then there was so much torque, you’d get wheelspin through third and fourth gears.” Prepared with a Lucas-McKay mechanically timed individual-stack magnesium fuel-injection induction system that was paired with ported production car double-hump iron heads, a rev-kit fitted roller lifter camshaft, roller bearing rocker arms, and a virtually stock production crankshaft, it had a lasting impact on the series' ability to conduct high car-count finishes and close competition events by the degree of mechanical success it provided to a series filled with star international Grand Prix drivers like David Hobbs, Brian Redman, Jody Scheckter and Mario Andretti.


The 327 cu in (5,354 cc) V8, introduced in 1962, had a bore of 4 in (101.6 mm) and a stroke of 3.25 in (82.55 mm). Power ranged from 210 hp (157 kW) 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-76 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). It's also interesting to note that in 1965 Chevrolet released the now legendary L-79, which was nothing more than an L-76 (11.0:1 forged pop-up pistons, forged steel rods and crank, 2.02 Corvette heads), but with the 30-30 Duntov cam replaced by the #151 hydraulic cam. The 327-350 hp engine could give many big blocks a run for their money.

In 1966, Checker began offering the 327 as an option.[5] The Avanti II and its successors were powered by the 327 and later versions of the small-block V8.

In 1968, the 327 was exported to Australia for use in the Holden HK Monaro GTS327. The engine was used in the Monaro after development of the locally made Holden V8 engine fell behind schedule. The 327 was replaced in the 1969 Monaro by the 350.


The 350, with a 3.48-inch (88.4 mm) stroke, first appeared as a high-performance L-48 option for the 1967 Chevrolet Camaro. One year later it was made available in the Chevrolet Nova, and finally in 1969 the rest of the Chevrolet line could be ordered with a 350. The engine was also exported to Australia where it appeared in the Holden Monaro from 1969 through 1972.

Many variants followed:

  • L46

Years: 1969-1970 The L46 became an optional engine for the 1969 Chevrolet Corvette. It was a higher performance version of the base 350 cu in V8 with casting number 492 2.02"/1.60" valve heads and had an 11:1 compression ratio (high octane gas must be used) and produced 350 bhp.[6] It was also available in 1970. 4bbl Quadrajet carburetor and L46 hydraulic cam, dome piston (+2.6 cc), 186 heads, and a four-bolt block.

  • L48

Years: 1967–1980

The L48 is the original 350 cu in (5.7 L), solely available for 1967 in the Super Sport version of Camaro SS 350 (1967-up) or Chevy II/Nova in 1968-1979. In 1969 it was used in almost all car lines; Camaros, Impalas, El Caminos, Chevelles & Novas. 1969 L48's use a Hyd Cam, 4bbl Quadrajet carburetor, cast pistons, 4-bolt main casting number 010 Blocks & casting number 041 or 186 heads. Power output was 300 hp SAE and 380 lb·ft (520 N·m) torque. Compression ratio was 10.25:1. The compression ratio of the L48 was lowered to 8.5:1 in 1971.

In 1972 the only way to get a L48 (4bbl V8) in a Chevrolet Nova was to get the Super Sport Package. This is indicated by the fifth digit in the VIN being a "K". 1972 was the only year you could verify the Super Sport package by the VIN.

The L48 V8 was the standard engine in the 1975–1980 Chevrolet Corvette. The L48 V8 Corvette engine produced 165 bhp in 1975. Power increased to 180 bhp in 1976 and stayed the same in 1977. 1978 saw 175 bhp for California or high altitude areas and 185 bhp for everywhere else. Power increased to 195 bhp in 1979 and decreased to 190 bhp in 1980.[6]

  • L65

The 2bbl carburetor 145HP version of the LM1 350".

  • LM1

The LM1 is the base 5.7 L (350 cu in) with a 4-barrel carburetor (usually with a Rochester Quadrajet) 155-175 hp engine in passenger cars to 1979 as a retail option (its final use with a retail passenger car was the 1981 Camaro Z28) and police package 9C1 A/G (Malibu to 1981) and B-bodies (Caprice, Impala) until 1988 (retail market GM rear wheel drive/V8s sold to the general public had a maximum 5.0L displacement with the exception of its musclecar survivors e.g. Corvette and F-bodies (Camaro IROC Z or Trans Am). Throughout its lifespan, it received either a points, electronic, and/or computer-controlled spark system, to conventional and feedback carburetors. The LM1 was superseded by the L05 powerplant after 1988.

  • ZQ3

Years: 1970-1974 The ZQ3 was the standard engine in the 1970–1974 Chevrolet Corvette. It was a 300 bhp version of the 350 cu in small-block, with 10.25:1 compression and hydraulic lifters. It used a Rochester "4MV" Quadra-Jet 4-barrel carburetor.[7] 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 supposedly had a lower nickel content but thicker cylinder deck, and post 1974 heads of the small block Chevrolet used less iron, and were lighter weight, crack-prone, and less powerful because of the lower compression ratios used.

In 1971, power decreased to 270 (gross) bhp and 300 (gross) lb-ft of torque with 8.5:1 compression. 1972 saw 200 (net) bhp and 270 (net) lb-ft of torque. In 1973 power decreased to 190 bhp, but increased slightly in 1974 to 195 bhp.[6]

  • LT-1
LT-1 from a 1970 Chevrolet Camaro Z28

Years: 1970–1972

The LT-1 was the ultimate 350 cu in V8, becoming available in 1970. It used solid lifters, 11:1 compression, the '178' high-performance camshaft, and a 780 CFM Holley four-barrel carburetor on a special aluminum intake, with rams' horn exhaust manifolds in the Chevrolet Corvette, Delco transistor ignition and a low-restriction exhaust factory rated at 370 bhp in the Corvette, and 360 bhp at 6000 rpm and 380 lb-ft at 4000 in the Camaro Z28[8] (the NHRA rated it at 425 hp for classification purposes). Redline was 6500 rpm but power fell off significantly past 6200 rpm. The LT-1 was available in the Corvette, and Camaro Z28. Power was down in 1971 to dual-rated 330 bhp, 255 nethp and 360 lb-ft of torque with 9:1 compression, and again in 1972 (the last year of the LT-1, now rated using net only, rather than gross, measurement) to 255 bhp and 280 lb-ft.

The "LT1" designation was later reused on a Generation II GM MPFI "350" small block engine in late 1991, the LT1.

  • L82

Years: 1973–1980

The 1973–1974 L82 was a "performance" version of the 350 that still used the casting number 624 76cc chamber "2.02" heads but with a Rochester Quadra-jet 4bbl carburetor and dual-plane aluminum intake manifold, the earlier L46 350 hp 350 hydraulic-lifter cam, and 9:1 compression forged-aluminum pistons producing 250 bhp (`71 was the first year for SAE net hp rating, as installed in the vehicle with accessories and mufflers) and 285 lb-ft of torque. Its cast-aluminum LT-1 valvecovers were painted crinkle-black contrasting with the aluminum manifold and distributor housing. It was down to 205 bhp and 255 lb-ft of torque for 1975. It produced 210 bhp in the Corvette for 1976-1977. The 1978 L82 recovered somewhat, producing 220 bhp and 260 lb-ft in the Corvette and in 1979 it produced 225 bhp in the Corvette. In 1980, its final year, it produced a peak of 230 bhp.[6] This engine was also available on the Chevrolet Camaro.

  • L81

Years: 1981

The L81 was the only 5.7 L (350 cu in) Corvette engine for 1981. It produced 190 bhp and 280 lb-ft of torque from 8.2:1 compression, exactly the same as the 1980 L48, but added hotter cam and computer control spark advance, replacing the vacuum advance.[7] The L81 was unique in that it was the only Corvette engine that employed a "smart carburetor." The Rochester Quadrajet from 1980 was modified to allow electronic mixture control, and an ECM (Engine Control Module), supplied with data from an exhaust oxygen sensor, modified the fuel/air mixture being fed to the engine.

  • LT-9

Years: 1981-1986[9]

The LT-9 served as GM's truck-based Heavy Emissions[10] variant of the 5.7 L (350 cu in) supplied in K20/K30 pickups and with the P30 chassis used for motorhomes and stepvans.

The LT-9's listed specifications are 160 bhp @ 3800 rpm and 250 lb-ft of torque @ 2800 rpm with 8.3:1 compression.[11] LT-9's are carbureted with Rochester Quadrajets from factory and are generally 4-bolt mains. The LT-9 is often known by VIN code as the "M-code 350."[10]

  • L83

Years: 1982, 1984

The 1982 L83 was again the only Corvette engine (and only available with an automatic transmission) producing 200 bhp and 285 lb-ft of torque from 9:1 compression. This was again the only engine on the new 1984 'Vette, at 205 bhp and 290 lb-ft of torque. 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.[6]

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

Years: 1985–1992

The new 1985 L98 350" added tuned-port fuel injection "TPI", which was standard on all 1985–1991 Corvettes. It was rated at 230 bhp for 1985–1986, 240 bhp for 1987-1989 (245 bhp with 3.07:1 rear axle ratio (1988-1989 only)), and 245 bhp in 1990-1991 (250 bhp with 3.07:1 rear axle). Aluminum cylinder heads (Corvette only) were released part way through the 1986 model run, modified for 1987 with D-ports, and continued through the end of L98 Corvette production in 1991 (still used on ZZx 350 crate engines).[7] The L98 V8 was optional on Jan. '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 and a change to hydraulic roller camshaft. Compression was up again in 1990 to 9.5:1 Camaro/Firebird and 10:1 Corvettes, but rated output stayed the same.

  • L05

The L05 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 1991 which includes chassis cabs and 4-door crew cabs. Although usage was for trucks, vans, and 9C1-optioned Caprices, the L05 was also used with the following vehicles:

LO5s were used primarily with casting number 14102193 (64cc combustion chambers) cylinder heads with swirled intake ports - the intake ports were designed for fuel economy (the design was also shared with the 103 heads used on the 4.3L with TBI). The swirl ports (known to GM as a vortex chamber) along with the irregular shape of the combustion chambers limit the airflow and horsepower output where they did not provide a fast burn, later phased in with the 1996+ Vortec heads. A majority of the LO5s used with the truck/vans had conventional flat tappet camshafts while the Caprice 9C1 (1989–93) had a roller cam. L05 usage was replaced by the 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.

  • L31

The Vortec 5700 L31 (Vin code 8th digit "R") is a V8 truck engine. Displacement is 5.7 L. It is the last production Generation I small-block from Chevrolet. The cylinder heads feature combustion chambers and intake ports very similar to those of the LT1 V8, but without the reverse-flow cooling. As such, the L31 head is compatible with all older small-blocks, and is a very popular upgrade. It offers the performance of more expensive heads, at a much lower cost. It does, however, require a specific intake manifold (A 5.7L, 350 CI L31, Vortec engine has eight bolts attaching the intake manifold or four per head, as opposed to the traditional six bolts per head twelve in total found on older Chevrolet small blocks). The L31 was replaced by the 5.3 L 5300 LM7. The 2002 model year was the final year for the L31 5.7 L small block V-8 whose origins date back to 1955. The Vortec 5700 produces 255 hp (190 kW) to 350 hp (261 kW) at 4600 rpm and 330 lb·ft (447 N·m) to 350 lb·ft (475 N·m) of torque at 2800 rpm. It is currently being produced as a crate engine for marine applications and automotive hobbyists as the 'RamJet 350' with minor modifications. 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 despite its cast iron construction. Using this "MARINE" intake will allow the use of common types of Bosch-style injectors with various flow rates while still maintaining emission compliance.

L31 applications:

TBI L31 applications

  • 1996 G-Series vans over 8,500 lb (3,856 kg) GVW w/ 4L80E transmission

Special applications

4.125 in bore family (1970–1980)[edit]


The 400 cu in (6.6 L) is the only engine in this family and was introduced in 1970 and produced for 10 years. It has 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 and therefore required 'steam' holes in the block, head gaskets, and heads to help alleviate 'hot-spots' in the cooling system at the point above the siamesed cylinders. Overheating and damage are likely if head gaskets or heads without 'steam' holes are used on a 400 block. The 400 is the only engine that uses a 2.65" main bearing journal and a 2.10" rod bearing journal. The connecting rod was also 400 specific being 5.565" as opposed to the 5.7" rod used in all other small block Chevrolet engines. The 400 was made in 4-bolt main journal from 1970 to 1972 and in 2-bolt main journal from 1973 to 1980. The 400 can have either 2 or 3 freeze-plugs per side though all 400 blocks have the provisions for a 3rd freeze-plug on each side. The 400 was rated at 245–265 horsepower (gross[150–180 HP net]) through its life. The 400 saw extensive use in full-size Chevrolet and GMC trucks; K5 Blazer/Jimmy, 1/2-ton, 3/4-ton, 1-ton, and even larger 'medium duty' trucks had an option to be equipped with a 400. The engine was available in midsize A-Body and full-size B-Body passenger cars until the end of the 1976 model year. Early models produced 265 horsepower with a two-barrel carburetor. All 400s came with a two-barrel carburetor with a four-barrel carburetor option becoming available in 1974. The 400 was never intended as a high-performance engine and never saw large factory horsepower numbers;however, it did develop a reputation for creating a tremendous amount of torque and has since become popular for many types of racing, both on and off road.

3.671 in bore family (1975–1976)[edit]


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 133 lb·ft (180 N·m) at 3600 rpm. The 262 was replaced by the 305 for the 1977 model year.

This was Chevrolet's second 4.3 L-displacement powerplant; four other Chevrolet engines displaced 4.3 L: the Vortec 4300 (a V6 based on the Chevrolet 350, with two cylinders removed), the original 265 V8 in 1955, a stroked version of the stovebolt-era 235 inline six displacing 261 cubic inches, 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:

3.736 in bore family (1976–1998)[edit]


Designed and built during the era of the gas embargo, CAFE mandates, and tighter emissions, this engine family was designed to become Chevrolet's cost-effective, all-purpose "economy V8" engine line. These were intended to fill the gap where the venerable 283 ('57-'67), & 307 ('68-'73) had been. Bore and stroke were 3.736 in (94.9 mm) by 3.48 in (88.4 mm), utilizing the 350's crankshaft throw. This new engine family would provide better gas economy than the 350, share its basic architecture and many parts with the 350 (thus reducing production costs), and provide customers with more horsepower/torque than Chevrolet's 1970s-era inline 6 and V6 engines. During the early 1980s, when GM was streamlining their engine lineups, the Chevrolet 305 would rise to prominence as General Motors' "corporate" engine, signified by being the standard (and often only) V8 in many GM vehicles. Through much of the 80's, the 305 became General Motors' most common V8, followed closely by Oldsmobile's robust 307. The Chevrolet 305 also became the standard V8 in GM's C/K truck series, and was even used in the Corvette for one year in 1980.

Crankshafts used with the 305 had the same casting number as the 350 with one discernable difference - the 305 crank is lighter in weight to compensate for engine balancing. (The bobweights are reduced in size which makes it unsuitable for use in a 350 where metal would have to be welded back on.) The medium journal 305, like its big-brother 350, would be further developed in the 1990s, although with a reduced 3.00" stroke (using 5.94" connecting rods), into the "Generation II SBC" GM LT-Series engine L99 263.

Introduced in 1976 models, it had a displacement of 305 cu in (5.0 L) The 305 was used in the following cars:

The Chevrolet 305 is a reliable, fuel efficient V8, easily capable of 200,000 miles, if maintained. From 1976 onward into the early 1980s, these engines were also prone to wearing out their camshaft's lobes very prematurely due to a combination of improper manufacturing and reduced/poor quality controls (a result of GM cost-cutting measures). The 305 is sometimes dismissed in performance circles because of its "lack of power", its small bore size, and difficulty flowing large volumes of air at higher rpms; however, two variants of the '83-'92 305 were notable performers, especially when in comparison to most of the other "performance engines" of that time: the '83 -'88 L69 "High Output 5.0L" (only used in late '83 -early '86 F-body/ late '83 -'88 Monte Carlo SS) and the '85 -'92 LB9 "Tuned Port Injection 5.0L" (F-body only).

After 1993, its usage was limited to light trucks and SUVs until the 2000 model year (vans and commercial vehicles until 2003). The 305 was sold as a crate motor under the Mr. Goodwrench brand as a replacement motor and as a boat engine for Mercury Marine until late 2014 when it was discontinued.

Year hp (kW) lb•ft (N•m)
1976 140 (104) 250 (339) w/2bbl.
1977 145 (108) 245 (332) w/2bbl.
1978 140 (104) 240 (325) w/2bbl.
1978 160 (119) 235 (319) w/4bbl.
1979 130 (97) 245 (332) w/2bbl.
1979[a] 125 (93) 235 (319) w/2bbl.
1980 155 (116) 240 (325) w/4bbl.
1981 150 (112) 240 (325) w/4bbl

a Note: California Emissions

  • LG3


This variant used a Rochester 2GC from 1976 to 78. In 1979, the more fuel-efficient Rochester Dual-Jet 2bbl carburetor replaced the older 2GC. This change also resulted in a drop in the horsepower rating to 130 hp (125 for California emissions cars). All years had an 8.5:1 compression ratio.

  • LG4

Years: 1980–1988*

The LG4 produced 150 hp (112 kW)-170 hp (127 kW) and 240 lb·ft (325 N·m)-250 lb·ft (339 N·m). Introduced in 1978, the LG4 was essentially an LG3 with the addition of a 4-bbl carburetor. The engine saw a series of gradual improvements, increasing reliability, mpg, and power output through its production run. In 1981 (1980 for California models) Chevrolet added GM's new "Computer Command Control" (CCC) engine management system to the LG4 engines (excpet Canadian models). The CCC system included the electronic Rochester 4-bbl E4ME Quadra-Jet, where the primary side of the carburetor had the fuel metering controlled by computer. In 1983, Chevrolet replaced the cast iron intake with an aluminum version and utilized either 14014416 ("416") or 14022601("601") heads with int: 1.84/ exh: 1.50 valves, 58cc chambers, 178cc runners. For 1985, the 4-valve-relief, flat top pistons from the L69 were added to the LG4 which resulted in an increase in compression. Also added was a knock sensor to allow the "CCC" engine management system to compensate for the increase in compression and a more aggressive spark timing map in the ECM. As a result, power increased for the 1985models to 165 hp (123 kW) from the 150 hp (112 kW) rating in 1984. For 1986, Chevrolet changed over to a 1 piece rear main seal engine block design to minimize leaks and warranty claims, however some early '86 blocks retained a 2 piece rear main seal.

For 1987, Chevrolet once again made some revisions to increase overall reliability. An all-new electronic distributor design (with a smaller distributor cap) was used. The intake manifold to head bolt pattern was redesigned to improve gasket integrity - four of the center intake manifold bolts were drilled at 72 degrees instead of 90 degrees for the cast iron cylinder heads. Changes to the valve covers were also made. "ribbing" was added to the top of the valve covers to increase surface area, acting as a heat sink. To improve intake gasket sealing, the mounting bolts were relocated to the valve cover centerline, placing all sealing pressure evenly upon the mounting flange perimeter... thus these became known as "centerbolt valve covers", first introduced in 1985 on the LB4 4.3L V6 and the Corvette a year earlier (the aluminum cylinder heads used with the Vette were the first to have the centerbolt valve covers). Another improvement was utilization of a hydraulic lifter/roller camshaft on most '87 LG4's. Some early engines have lifter retainer provisions, but utilize the older, non-roller camshaft. 1987 would also be the last year for the LG4 production, however a run of LG4 engines was made to supplement the carry-over production for the 1988 Monte Carlo and the 1988 Chevrolet Caprice.

  • LU5

Years: 1982 – late-1983

The LU5 "Crossfire EFI 5.0L" featured a dual Throttle Body Injection set-up, based upon the original "Crossram Intake" supplied by Chevrolet for the 1969 Camaro Z28. Unlike, the original '69 version, Chevrolet did not place it in the trunk for owners to install. The system utilized a special version of GM's still-new "CCC" engine management system. Fuel was supplied by the two TBI units, set diagonally apart from each other, atop the unique, aluminum intake manifold. Unfortunately, the system was placed atop the basic LG4 and lacked any significant performance capability. The engine was originally planned for the long awaited '82 Camaro Z28, however due to a last-minute GM-mandated cancellation of Pontiac's 301 V8 production & Turbo 4.9L Project (T301), the Crossfire 305 was made available in the '82 Trans Am. A 350 cubic inch version was also used in the Corvette. Being fairly early into GM's electronic engine management development and electronic fuel injection programs, few dealerships had the technology, equipment, or properly trained mechanics capable of dealing with these engines. Compounding these problems were widely varying fuel quality standards, production issues, poor quality control by GM, & owners who tinkered with a system they did not understand. In a very short time, these engines obtained the notorious nickname; "Ceasefire Engine". Today, owners with these engines note that they are fairly reliable, and that a significant upgrade can be made by simply using the L69/LB9 TPI/L98 TPI exhaust manifolds/ exhaust systems... When combined with performance-built stock 305 heads w/larger valves or aftermarket heads, plus a camshaft upgrade, these engines can perform surprisingly well. Thanks mostly to a somewhat cult-like following, a number of aftermarket performance parts are also available through Crossfire-specialized manufacturers.

  • L69

Years: late-1983 – 1988

The L69 "High Output 5.0L" was released late into the 1983 model year. It was optional only in the "Firebird Trans Am" and "Camaro Z28" & "IROC-Z", and was Standard in the revived "Monte Carlo Super Sport" (no other GM models were available with this engine).

The L69 features a compression ratio of 9.5:1, 4-relief flat top pistons, a unique & relatively aggressive stock camshaft, GM PN: 14088843* hydraulic flat tappet - duration @ .050": 202/206 - max lift: .403/.415 - 115 - idle: 650 rpm... *(not a camshaft taken from another Chevrolet engine). It also utilizes a performance-tuned "CCC" ECM/PROM, a knock sensor, a performance-tuned E4ME 750CFM Rochester Quadra-Jet 4 barrel carburetor, and a special, free-flowing exhaust system with large diameter exhaust manifolds, Y-Pipe, catalytic converter, and exhaust system, (The L69 F Body exhaust system components would be revised slightly and used again on the later LB9 305 & L98 350 TPI engines). Additionally, the engines came equipped with a functional cold air induction hood on the '83-'84 Trans Am H.O., a dual snorkel air cleaner assembly on the '83-'86 Camaro Z28/IROC-Z H.O., & '85-'86 Trans Am H.O., and a large, single snorkel on '83 -'88 Monte Carlo SS (also, rare optional dual snorkel in '87-'88), an aluminum intake manifold, high stall torque converter in the Monte SS and 1984 F-Body, or a lightweight flywheel on T-5 eqipped F-Body's, and all utilized 3.73 axle gears (3.42 Standard in '84 F-Body/ THM700R4/optional w/3.73:1). The Monte Carlo SS featured a special HD version of the THM200-4R also used in the Buick Turbo Regal/GN and Olds Hurst/Olds-442.

The L69 engine produced 190 hp (142 kW) @ 4800 and 240 lb·ft (325 N·m) of torque @ 3200 rpm. in the F-Body and was rated at 180 hp in the Monte SS.

  • LE9

Years: 1981–1986

The LE9 5.0 L (305 cu in) was a truck/van/car version 4BBL 650CFM that also had a 9.5:1 compression ratio, the LM1 cam and 14010201 casting heads featuring 1.84/1.50" valves and 53 cc chambers. The engine made 165 hp (123 kW) @ 4,400 and 240 lb·ft (325 N·m) @ 2,000 rpm.

  • LB9

Years: 1985–1992

The LB9 "Tuned Port Injection 5.0L" was introduced in 1985. At its core was the stout L69 shortblock and it utilized the same aggressive L69 camshaft profile. The induction system was unlike any system used previously by GM. It featured a large plenum made of cast aluminum, with individual runners made of tubular aluminum, feeding air to each cylinder. And each cylinder had its own fuel injector fed by a fuel rail mounted above each bank. In 1985, this engine was optional only in the "Camaro IROC-Z" and "Trans Am" equipped with the WS6 performance suspension. In the Corvette, a 350ci version of this engine, the L98, was would be two years before the L98 would be offered in the F-Body. The LB9 was also available in the '87-92 GTA and Firebird Formula. 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.

  • L03

Years: 1987–95

The L03 produced 170 hp and 255 lb·ft (346 N·m) of torque; 170 hp at 4,400 rpm and 275 lb·ft (373 N·m) at 2,400 in 1993–1995 GM trucks. This engine used the TBI throttle-body fuel injection. It featured "swirl port" heads and served as the base engine in all C/K 1500 Series GMC/Chevrolet Trucks/Vans.

  • L30

Years: 1996-2003

The Vortec 5000 L30 is a V8 truck engine. Displacement is 5,013 cc, (305.9 cubic inches). Bore is 95 mm (3.7 in), stroke is 88.4 mm (3.5 in). The compression ratio is 9.1:1.[12] It is a based on the Generation I small-block from Chevrolet. It was replaced by the 4.8 L 4800 LR4 for the 2003 full-size vans. In van configuration it produces 220 hp (164 kW) net flywheel at 4,600 rpm and 290 lb·ft (393 N·m) net flywheel torque at 2,800 rpm. The engine uses a hydraulic roller cam and high flowing, fast burn style vortec heads. Differences include bore and stroke, intake valve size, and smaller combustion chambers. L30 applications:

262 L99 4.3L V8[edit]

The L99 4.3 L (262 in3) V8 shared a 3.736 inches (94.9 mm) cylinder bore with the 305 in3 but had a 3 inches (76 mm) stroke compared to the 3.48 inches (88 mm) stroke of the 305 in3. The pistons used in the 4.3 L V8 were the same as the ones used in the Vortec 5000, but 5.94 inches (151 mm) connecting rods were used to compensate for the shorter stroke. It was designated by the RPO code L99, and was introduced in the 1994 model year. This was the base engine used in 1994-1996 Chevrolet Caprice Sedans, the 9C1 police package sedans and the 1A2 special service station wagons. The L99 was not available in other vehicles.

The L99 featured updated Generation II block architecture and is visually identical to the larger 5.7 L LT1 Generation II V8. Like the LT1, it features sequential fuel injection, reverse-flow cooling, and an optical ignition pickup. Output is 200 hp (150 kW) and 245 lb·ft (332 N·m). Due to its smaller displacement, the L99 provided higher EPA fuel economy ratings than the 5.7 L LT1. The L99 was produced for the 1994-1996 model years.

3.50 in bore family (1979–1982)[edit]


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 CID engine had the 350's crankshaft stroke of 3.48" and the smallest bore of any small-block, 3.500 in (88.9 x 88.4 mm).

It was only available with a Rochester Dualjet 210 – effectively a Rochester Quadrajet with no rear barrels. After 1980, electronic feedback carburetion was used on the 267. The 267 also saw use in 1980 to 1982 Checker Marathons.[13]

While similar in displacement to the other 4.3L(265)–4.4L(267) 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 (5.0 L) as their base V8 engine.

Major changes[edit]

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 boss that was added to the left rear cylinder block casting and machined for this purpose.
  • 1957 – The displacement of the base V-8 continued at 265 cubic inches, but optional V-8 engines were introduced with a displacement of 283 cubic inches.
  • 1958 – Bosses for side motor mounts were added to the block casting, 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. Also, the cylinder head valve cover mounting bolt holes were changed from the top row staggered (relative to the bottom row of bolts) to the "straight-across" pattern that remained the way of identifying the early heads from the newer ones with a valve cover design which lasted until the 1987 center-bolt-style covers.
  • 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 stroke, was introduced.
  • 1967 - The oil filter mounting now came from the factory with an adapter and machining to allow the use of spin-on filters; canister mounting was possible by removing the adapter.
  • 1968 – The main-journal diameter was increased from 2.30" (small) to 2.45" (medium), and the connecting-rod journal diameter was increased to 2.10" from 2.00". This allowed the use of cast-iron crankshafts; the previous crankshafts were made of forged steel, which was more expensive. The rod bolts were changed from 11/32" diameter to 3/8". The oil-fill location was moved from a tube on the front of the intake manifold to a cap on the left- or right-side valve cover, depending upon the application.
  • 1970 - The "400" is introduced in September 1969 for the 1970 model year, with a bore of 4.125" and a stroke of 3.75". This engine introduced the "large-journal" crankshaft with a main journal size of 2.65" and rod bearing journals of 2.10". This engine also introduced "Siamese bores" to the Chevrolet small-block line, requiring "steam holes" in the cylinder heads and head gaskets, which were used to prevent hot spots and subsequent overheating. The connecting rods, due to the long stroke, are also shorter at 5.565", differing from all other 5.7" small-block connecting rods.
  • 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 as requiring an externally balanced flexplate/flywheel.
  • 1987 – The valve cover surfaces were changed so that the mounting lip was raised and the bolt location was moved from 4 bolts on the perimeter to 4 bolts along the centerline of the valve covers (this design debuted on the Corvette in 1986, and the Chevrolet 4.3L 90 degree V6 the year before). Also changed were the mounting angles of the two center bolts on each side of the intake manifold (from 90 to 73 degrees), and the lifter bosses were increased in height to accept roller lifters; the aluminum-alloy heads for use on the Corvette engines retained the non-angled bolts. Also, all carburetors(except some 1987-89 F-body and B-body models, also the 30 and 3500 model 1-ton trucks through 1989 with either the M-code 350 or W-code 454 engines, in which all retained the 4bbl rochester E4ME carbs) were replaced by TBI (throttle-body injection) fuel injection.
  • 1996 – This was the last change for the Generation I engine, which 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 bolts. The cylinder block timing cover lip was thickened for use with the plastic timing cover (redesigned for use with a crankshaft position sensor with integrated dowel pins - cylinder blocks for 1996+ do not have dowel pins in the timing cover flange) held with 8 bolts and the water pump bypass hole on the RH deck and below the water pump passage undrilled. Also the fuel pump boss is still present but undrilled (which dates back to the 1992 model year).


Chevrolet Generation I V-8 Small Block Engine Table

note 1: depending upon vehicle application; horsepower, torque, and fuel requirements will vary.

Gen I Years Engine option code (VIN identifier) Power (hp) Torque (lb.-ft.) Displacement (c.i.) Fuel (octane) Bore x Stroke (in) Compression ratio Block & heads (iron or aluminum) Block features
I 1996-02 L30 (M) 220@4600 290@2800 305 3.7 x 3.5 9.1:1 Iron Truck only
I 1987-95 L03 (E/H) 170@4400 255@2400 305 3.7 x 3.5 9.1:1 Iron TBI
I 1988-96 L05 (?) 210@4400 300@2800 350 4.0 x 3.48 9.3:1 Iron TBI
I 1978-88 LG4 (F/H) 150-170@4600 240-250@2800 305 3.7 x 3.5 9.1:1 Iron 4bbl
I 1981-86 LE9 (?) 165@4400 240@2000 305 3.7 x 3.5 9.5:1 Iron
I 1982-83 LU5 (?) 305 3.7 x 3.5  ?:1 Iron "Crossfire EFI 5.0L"
I 1967-80 L48 (K) 165-195 380 350 4.0 x 3.48 8.25-10.5:1 Iron
I 1969-70 L46 (?) 350 350 93req 4.0 x 3.48 11.0:1 Iron
I 1987-95 L65 (?) 145 350 4.0 x 3.48 Iron 2bbl
I 1988 LM1 (?) 155-175 350 4.0 x 3.48 Iron 4bbl
I 1970-74 ZQ3 (?) 190-300 270-300 350 4.0 x 3.48 8.5-10.25:1 Iron 4bbl, Corvette
I 1970-72 LT1 (?) 330-370@6000 270-300@4000 350 4.0 x 3.48 9.1:1 Iron TBI
II 1991-?? LT1 (?) 305 4.0 x 3.48 Iron
I 1973-80 L82 (?) 205-250 255-285 350 4.0 x 3.48 9:1 Iron TBI
I 1981 L81 (?) 190 280 350 4.0 x 3.48 8.2:1 Iron TBI
I 1981-86 LT9 (M) 160@3800 250@2800 350 4.0 x 3.48 8.3:1 Iron 4bbl, truck
I 1982-84 L83 (?) 200-205 285-290 350 4.0 x 3.48 9.0:1 Iron CrossFire
I 1985-92 L98 (?) 225-250 330-345 350 4.0 x 3.48 9.5-10:1 Iron/Aluminum (some) TPI
I 1996-02 L31 (R) 255-350@4600 330-350@2800 350 4.0 x 3.48 Iron truck, Vortec
I 1970-80 Lxx (?) 245-265 400 4.125 x 3.75 Iron 70-72 4bolt main, 73-80 2bolt main
I 1975-76 Lxx (?) 110 133@3600 262 3.736 x 3.0 Iron TBI
I 1994-96 L99 (?) 200 245 262 3.736 x 3.0 Iron reverse cooling, Caprice, special ops, police vehicles
I 1983-88 L69 (?) 180-190@4800 240@3200 305 3.7 x 3.5 9.5:1 Iron H.O., Firebird/Camaro only
I 1985-92 LB9 (?) 190-230 275-300 305 3.7 x 3.5 Iron TPI, Firebird/Camaro only
I 1976-80 LG3 (?) 170@4400 255@2400 305 3.7 x 3.5 8.5:1 Iron 2bbl

Generation II GM small-block (1992–1997)[edit]

Generation II
Manufacturer General Motors
Also called GM LT engine
Production 1992-1997
Combustion chamber
Configuration V8
  • 4,321 cc (263.7 cu in)
  • 5,727 cc (349.5 cu in)
  • 5,733 cc (349.8 cu in)
Cylinder bore
  • 95.0 mm (3.74 in)
  • 99.0 mm (3.90 in)
  • 101.6 mm (4.00 in)
Piston stroke
  • 76.2 mm (3.00 in)
  • 88.39 mm (3.480 in)
  • 93.0 mm (3.66 in)
Cylinder block alloy
Cylinder head alloy
Fuel system
Fuel type
Oil system Wet sump
Cooling system Water-cooled
Predecessor Generation I
Successor Generation III

General Motors' Generation II LT is a small block V8 engine. Making its debut in the 1992 Chevrolet Corvette, the new LT sought to draw upon the heritage of the 1970 Chevrolet LT-1.

A significant improvement over the original Generation I V8 is the Generation II LT's "reverse cooling" system, allowing coolant to start at the heads and flow down through the block. This keeps the heads cooler, affording greater power through a higher compression ratio and greater spark advance at the same time it maintains higher and more consistent cylinder temperatures.

Some parts from the Generation II are interchangeable with the Generation I one-piece rear main seal engine. The interchangeable parts include the rotating assembly (crank shaft, pistons, connecting rods, and flywheel/flexplate) and valvetrain assembly (not including timing set, which includes a gear to drive the water pump). The LT uses a new engine block, cylinder head, timing cover, water pump, intake manifold and accessory brackets. The harmonic damper also does not interchange; it is a unique damper/pulley assembly. Engine mounts and bell housing bolt pattern remain the same, permitting a newer engine to be readily swapped into an older vehicle.

4.00 in bore blocks[edit]

5.7 L[edit]

GM LT1 from a 1993 Chevrolet Camaro Z28.

In 1992, GM created a new-generation small-block engine called the "LT1 350", not to be confused with the high-output Generation I LT-1 of the 1970s. It displaced 5.7 L (350 cu in), and was a 2-valve pushrod design. The LT1 used a reverse-flow cooling system which cooled the cylinder heads first, maintaining lower cylinder temperatures and allowing the engine to run at a higher compression than its immediate predecessors.

This engine was used in:

There were a few different versions of the LT1. All feature a cast iron block, with aluminum heads in the Y and F bodies, and cast iron heads in the B and D bodies. Corvette blocks had four-bolt main caps, while most other blocks were two-bolt main caps. Block castings remained the same between 2 and 4 bolt mains.

The 92–93 LT1s used speed density fuel management, batch-fire fuel injection and a dedicated Engine Control Module (ECM). In 94 the LT1 switched to a mass airflow sensor and sequential port injection. A new, more capable computer controlled the transmission as well as the engine and got a new name: Powertrain Control Module (PCM). Where the EC5M held its calibration information in a replaceable PROM chip, the 94-95 OBD1 PCMs are reprogrammable through the diagnostic port.

The early Optispark distributor had durability problems and a revised version was introduced with vacuum vents to remove moisture on the 1994 B-Bodies and in 1995 on the Y and F-Bodies; the vacuum vents can be added onto earlier distributors.[14] 1996 saw major revisions for OBD-II: a second catalytic converter on the F-body cars and rear oxygen sensors to monitor catalyst efficiency. Some OBD-II features had been added to the Corvette starting in 1994 for testing purposes.[citation needed] The 1997 model year Camaro and Firebird were the last year for this engine in a GM production car before it was replaced by the LS1, which was already in the Corvette for 1997.

The 1992 LT1 in the Y-body was factory rated at 300 hp (220 kW) and 330 lb·ft (447 N·m). 96 LT1 Y-bodies were rated at 300 hp (220 kW) and 340 lb·ft (461 N·m). The 93–95 F-bodies were rated at 275 horsepower (205 kW) and 325 lb·ft (441 N·m), while the 96–97 cars were rated at 285 horsepower (213 kW) and 335 lb·ft (454 N·m). The 96–97 WS6 and SS F-bodies were rated at 305 hp (227 kW). The 94–96 B and D-body version was rated at 260 horsepower (190 kW) and 330 lb·ft (447 N·m).


The LT4 was a special high-performance version of the new-generation LT1. With the addition of a slightly more aggressive camshaft profile, 1.6:1 roller aluminum rocker arms, high-flow intake manifold (painted red) with extra material above the port available to allow port matching to the raised port LT4 cylinder heads, it was rated at 330 horsepower (250 kW) and 340 lb·ft (461 N·m). It was introduced in the 1996 model year, for the last year of the C4 Corvette, and came standard on all manual transmission (ZF 6-speed equipped) C4 Corvettes. The engine was passed down to special versions of the Camaro and Firebird the next model year.

The LT4 was available on the following vehicles:

  • 1996 Chevrolet Corvette when equipped with 6-speed manual transmission (includes all Grand Sports) (Production: 6,359)
  • 1997 Chevrolet Camaro SLP/LT4 SS 6-speed (Production: 100 for the U.S., 6 for Canada. There were 2 prototypes)
  • 1997 Pontiac Firebird SLP/LT4 Firehawk 6-speed (Production: 29)

All 135 production engines for the Firehawks and Camaro SS were completely disassembled, balanced, blueprinted and honed with stress plates. One in 5 engines was tested on a Superflow engine dyno and every car was tested on a chassis dyno in addition to performing a short 6-mile (10 km) road test.

3.736 in bore blocks[edit]

4.3 L[edit]


A 260 in3 (4.3 L) was based on a 305 in3 with updated block architecture to be Generation II and a reduced 3 inches (76 mm) stroke. It was designated the L99, and was introduced in 1994 for the Chevrolet Caprice. It was externally identical to the LT1, but the bore was decreased to 3.736 inches (94.9 mm) and the stroke to 3 inches (76 mm) giving it a displacement of 263 in3. The pistons used in the L99 were the same as the ones used in the Vortec 5000, but 5.94 inches (151 mm) connecting rods were used to compensate for the shorter stroke. This was the base engine used on all 1994-1996 Chevrolet Caprice Sedans, including the Police Package vehicles.

Like the LT1, it features sequential fuel injection, reverse-flow cooling, and an optical ignition pickup. Output is 200 hp (150 kW) and 245 lb·ft (332 N·m). Due to its smaller displacement, it provides better fuel economy than the 5.7 L LT1, but at reduced horsepower & torque levels.

3.90 in bore blocks[edit]

5.7 L[edit]

A GM LT5 engine

For model year 1990, Chevrolet released the Corvette ZR-1 with the radical overhead cam LT5 engine, which shared only the 4.4 inch bore spacing with any previous LT engine. The LT5 was engineered by Lotus Engineering in the UK headed by design manager David Whitehead, with the engine being produced and assembled by Mercury Marine in Stillwater OK headed by Project Engineer Terry D. Stinson.[15] It was an all-aluminum 5.7 L (349 cu in) small-block V8, but was thoroughly different from any of the other Chevrolet 350 engines. The bore and stroke were both different at 3.9 by 3.66 in (99 by 93 mm) instead of the usual 4 by 3.48 in (102 by 88 mm) and it featured Lotus-designed 32-valve DOHC heads rather than the usual Chevrolet 16-Valve OHV Heads. It was hand built by specialty engine builder, Mercury Marine in Stillwater, OK. The preproduction LT5 initially produced 385 horsepower (287 kW), but was reduced to 375 horsepower (280 kW) and 370 lb·ft (502 N·m) for the 1990-1992 Corvette ZR-1. The power ratings jumped to 405 horsepower (302 kW) and 385 lb·ft (522 N·m) from 1993 until its final year in 1995, thanks to cam timing changes and improvements to the engine porting. 1993 also added 4-bolt main bearing caps and an exhaust gas recirculation system. The engine was used only in Corvettes.[16] A second generation of the LT5 was in the testing phase as early as 1993. What little information that survived showed that it would have utilized a duel plenum system similar to the first generation Dodge Viper as well as variable valve timing. The next generation LT5 was set to produce between 450 horsepower (340 kW) and 475 horsepower (354 kW). Unfortunately, the cost to produce the LT5 along with its weight, dimensions (would not fit the C5 pilot cars without extensive modifications) and internal GM politics over using an engine that was not designed and built in house killed the LT5 after six years of production. GM canceled the ZR-1 option in beginning in model year 1996. A total of 6939 were produced.[17] The LT5 however wasn't an evolutionary dead end. Despite being discontinued, a new class of premium V8s for Cadillac and eventually Oldsmobile, the dual overhead cam V8 Northstar and its derivatives, drew heavily from the LT5's design and lessons learned from its production.[18] GM also took lessons learned from producing a completely aluminum engine and applied them to the new LS series of engines.

The LT5 does not have reverse cooling and is generally not considered a small block Chevy.

The LT5 was available on the following vehicles:

  • 1990-1995 Chevrolet Corvette C4 ZR-1 equipped with 6-speed manual transmission (Production: 6,939). Although the LT5 was never used in another production GM vehicle, it did make its way into several Corvette concepts, race cars and even into a limited run of the Lotus Elise GT1.

LT6 and LT7[edit]

The LT6 and LT7 are not part of the LT family. See Oldsmobile Diesel engine for more information.

See also[edit]


  1. ^ Sherman, Dan (January 1, 2000). "The 10 Best Engines of the 20th Century". Ward's AutoWorld. 
  2. ^ "Chevy Corvette 1955 Technical Specifications". Unique Cars and Parts. 
  3. ^ Flory, J. "Kelly", Jr. American Cars 1960–1972 (Jefferson, NC: McFarland & Coy, 2004), p.341.
  4. ^ Braunschweig, Robert; et al., eds. (March 11, 1971). "Automobil Revue '71" (in German and French) 66. Berne, Switzerland: Hallwag SA: 242. 
  5. ^ Flory, p.411.
  6. ^ a b c d e Gunnell, John. Standard catalog of Corvette, 1953-2005. Krause Publications, 2004
  7. ^ a b c Gunnell, John. Standard Catalog of Corvette, 1953-2005. Krause Publications, 2004
  8. ^ Gunnell, John, 360 bhp with the Camaro's 'log' manifold exhaust system and points ignition. Standard Catalog of Corvette, 1953-2005. Krause Publications, 2004
  9. ^ "Chevy Truck Engine Specifications, RPO Codes, Horsepower, Displacement, Torque Ratings, - Chuck's Chevy Truck". Retrieved 2013-11-22. 
  10. ^ a b "LT9 engine - ChevyTalk -The Social Network for Chevy Fans". ChevyTalk. Retrieved 2013-11-22. 
  11. ^ Chevrolet Pickups 1973-1998: How To Identify Select And Restore Collector ... - Google Books. 2008-02-23. Retrieved 2013-11-22. 
  12. ^ "information on the Chevrolet C1500 w/ L30 engine". Retrieved 2012-01-25. 
  13. ^ Standard Catalog of Independents, pp. 41-42
  14. ^ Corvette Fever- Fixing An Opti-Spark Distributor Without Reaching For A Hammer. Andy Bolig
  15. ^ "Orbital Appoints Terry Stinson as Chief Executive Officer and Managing Director". Reuters. 2008-05-20. Retrieved 2012-06-04. 
  16. ^ "LT5 Engine Specs". 2012-02-28. Retrieved 2012-06-04.  // via
  17. ^ "ZR-1 FAQ". Retrieved 2012-06-04. 
  18. ^

External links[edit]