| Chevrolet small-block engine | |
| Manufacturer: | General Motors |
| Configuration: | 90° V8 |
| Block: | Cast iron, aluminum |
| Head: | Cast iron, aluminum |
| Fueltype: | Gasoline |
| Fuelsystem: | Carburetor, fuel injection |
| Coolingsystem: | Water-cooled |
| Timing: | Chain |
| Compression: | 8.2:1, 8.3:1, 8.4:1, 8.5:1, 8.6:1, 9.0:1, 9.1:1, 9.5:1, 10.25:1, 10.9:1, 11.0:1, 14.25:1[1] |
| Redline: | 4,800-7,200[2] |
| Power: | NaNhp[3] [4] |
| Torque: | NaNlbft[5] [6] |
| Weight: | [7] [8] [9] [10] |
| Predecessor: | Chevrolet Series D, Cadillac OHV, Oldsmobile "Rocket" OHV |
| Successor: | GM LS-based small-block engine |
The Chevrolet small-block engine is a series of gasoline-powered V8 automobile engines, produced by the Chevrolet division of General Motors between 1954 and 2003, using the same basic engine block. Referred to as a "small-block" for its size relative to the physically much larger Chevrolet big-block engines, the small-block family spanned from to in displacement. Engineer Ed Cole is credited with leading the design for this engine. The engine block and cylinder heads were cast at Saginaw Metal Casting Operations in Saginaw, Michigan.
LT1 and LT2 engines[11] are distinct from subsequent LS-based small-block engines.
The Generation II small-block engine is largely an improved version of the Generation I, having many interchangeable parts and dimensions. Later generation engines have only the rod bearings, transmission-to-block bolt pattern and bore spacing in common with the Generation I and II engines.[12]
Production of the original small-block began in late 1954 for the 1955 model year, with a displacement of, growing over time to by 1970. Among the intermediate displacements were the,, and numerous 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 305and small-block that became the GM corporate standard. Over the years, every GM division in America, except Saturn and Geo, used it and its descendants in their vehicles.
Finally superseded by the GM Generation III LS in 1997 and discontinued in 2003, the engine is still made by a General Motors subsidiary in Springfield, MO as a crate engine for replacement and hot rodding purposes. In all, over 100,000,000 small-blocks had been built in carbureted and fuel injected forms since 1955 as of November 29, 2011. The small-block family line was honored as one of the 10 Best Engines of the 20th Century by automotive magazine Ward's AutoWorld.[13]
In February 2008, a Wisconsin businessman reported that his 1991 Chevrolet C1500 pickup had logged over one million miles without any major repairs to its small-block V8 engine.[14]
All first- and second-generation Chevrolet small-block V8 engines share the same firing order of 1-8-4-3-6-5-7-2.
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. The engine quickly gained popularity among stock car racers, and was nicknamed the "Mighty Mouse," after the then-popular cartoon character, later abbreviated to "Mouse".[15] By 1957 the engine had grown to 2831NaN1. Fitted with the optional Rochester mechanical fuel injection (FI) and a Duntov high-lift camshaft, it was one of the first production engines to produce per . The 283 was adopted by other Chevrolet models, replacing the 265 V8s.
A high-performance 3271NaN1 variant followed, turning out as much as (SAE gross power, not SAE net power or the current SAE certified power values) and raising horsepower per cubic inch to . From 1954 to 1974, the small-block engine was known as the "Turbo-Fire" or "High Torque" V8. However, it was the 3501NaN1 series that became the best-known Chevrolet small-block.
Installed in everything from station wagons and sports cars to commercial vehicles, boats, industrial equipment, and even (in highly modified form) in aircraft, the 350 is the most widely-used small-block engine of all time. Though not offered in GM vehicles since 2003, the 350 series is still in production at a GM subsidiary in Springfield, Missouri, under the company's "GM Genuine Parts" brand, and is also manufactured as an industrial and marine engine by GM Powertrain under the "Vortec" name.
All Chevrolet V8s, from the big-blocks to today's LS7 and LS9, evolved from the 265/ small-block family. Of the three engines in this family, two of them, the 265 and the 283, made automotive history. The first of this family was the 265, introduced in 1954. The 265 had a 3.75inches bore. The stroke of the 265 was, like the 283.
The 2651NaN1 "Turbo-Fire" V8 was the second Chevrolet small-block; the first Chevrolet V8 was produced in 1917. The 265 cu in Turbo Fire engine was designed by Ed Cole's group at Chevrolet to provide a more powerful engine for the 1955 Corvette than the model's original " Blue Flame" in-line six, the 2-barrel debut version went from drawings to production in just 15 weeks.[16]
Cole's design borrowed the valve train design scheduled to be used at the time in the Pontiac V8. Internal GM rules at the time stated that once an automotive division had introduced a technological innovation, no other GM division could use it for a period of two years. The stud-mounted independent ball rocker arm design patented by Pontiac engineer Clayton Leach, was scheduled for introduction in the Pontiac 1955 V8. GM forced the Pontiac division to share its valvetrain design in Chevrolet's new 265 V8 in 1955, so that both engines were introduced the same year with the same valve train design. A side note to Pontiac's V8 was that the engine was supposed to be introduced with 1953 cars, and all 1953 and 1954 Pontiac cars' chassis and suspensions were designed for the engine that did not make it into a Pontiac until late 1954. This was because the Buick division lobbied GM to postpone the release of Pontiac's engine, as it affected Buick's release of its new OHV V8 engine.
A pushrod engine with hydraulic lifters, the small-block was available with an optional four-barrel Rochester carburetor, increasing engine output to, or in the Corvette. The short-stroke 3.75x bore × stroke engine's bore spacing would continue in use for decades.[17]
Also available in the Bel Air sedan, the basic passenger car version produced with a two-barrel carburetor. Upgraded to a four-barrel Rochester, dual exhaust "Power Pack" version, the engine was conservatively rated at, and with the "Super Power Pack," it was boosted up to the power level of the Corvette.
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 lack of adequate oil filtration leaves it typically only desirable to period collectors.
The 1956 Corvette introduced three versions of this engine— with a single 4-barrel carburetor, with twin 4-barrels, and with two four-barrel carburetors and a high-lift camshaft.
The 283 had a 3.875inches bore. The stroke of the 283 was, like the 265. The 283, famous for being one of the first engines to make one 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, which was a stroked 283 with a medium journal.
The 2651NaN1 V8 engine was bored out to in 1957, giving it a 2831NaN1 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 cast to accept the 3.875 bore. Five different versions between and were available, depending on whether a single carb, twin carbs, or fuel injection was used.
Horsepower was up a bit each year for 1958, 1959, 1960 (290hp), 1961 (315hp). The 1957 Rochester Ramjet mechanical fuel injection version produced an even one hp per one cu in (an impressive feat at the time. This was the third U.S.-built production V8 to produce one horsepower per cubic inch, after the 1956 Chrysler 300B and Desoto adventure .[18]
Besides being available in the Chevrolet line, it was optional in Checker Taxis beginning in 1965.[19] A version of it that was built by GM Canada was also available in Studebaker vehicles produced in Canada for 1965 and 1966.
A 3071NaN1 version was produced from 1968 through 1973. Engine bore and stroke was 3.875x. All 307s had large 2.45inches journals to accept the 327's crankshaft. Pistons used with the 307 share the same pin height as the 327 but retaining the 283's bore size.
Originally intended as the performance block, this engine family through the 3501NaN1 became an all-purpose engine that saw use in many applications from Corvettes to commercial vehicles. 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 2.45inches medium-sized journals. The first engine in this family was the small journal 327 in 1962 and the last being 2000s 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 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 from 1967 to 1969. It was the product of placing the 2831NaN1 3inches stroke crankshaft into a bore 3271NaN1 cylinder-block. The 1967 302 used the same crankshaft stroke as the 283, but was forged steel for high-performance duty. 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 diameter small-journal to a large-journal and a main-journal size that was increased from to . DZ 302.
The large-journal connecting rods were thicker (heavier) and used NaNinches 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 thicker 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 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 1969, 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 /0.030 in hot intake/exhaust valve-lash and Zora Arkus-Duntov (the first Duntov cam was the / 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 1964-1965 carbureted 327/365 and fuel injected 327/375 engines. It used the '202' / valve diameter high-performance 327 double-hump '186 and 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 3501NaN1/370 hp 1970 LT1 also used.
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. The first year had unique chrome valve covers with Chevrolet stamped into them without an engine displacement decal pad. In 1968, the engine had the chrome covers, but without the Chevrolet name, connected to a PCV valve and a chrome drop-base open-element air cleaner assembly fitted with a crankcase breather on a vacuum secondary Holley 4-Bbl carburetor. 1969 Corvette and 1970 Z/28 engines were also equipped with this Holley carburetor until the Q-jet carburetor returned in 1973. A 'divorced' exhaust crossover port heated well-choke thermostat coil was used to provide cleaner and faster engine warm-up. Its cast-aluminum distributor came in two styles, single-point had an ignition point cam designed to reduce point bounce at high rpm (Camaro) and transistorized (Corvette). Both distributors had a vacuum diaphragm to advance ignition timing at 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 aluminium valve covers with the LT1 350 Corvette engine. Conservatively rated at (SAE gross) at 5800 rpm and 290lbft at 4800, actual output with its production 11.0:1 compression ratio was around with primary x 3inches collector Sanderson tubular headers that came in the trunk when ordered with a 1967 Z/28, and associated carburetor main jet and ignition timing tuning. In 1968, the last year for factory headers, they had primaries x 3inches collectors. A stock 1968 Z/28 with the close-ratio transmission, optional transistorized-ignition and 4.88 gear, fitted with little more than the factory cowl plenum cold-air hood induction and headers, was capable of running 12.9 second/ NaNmiles times on street tires.
After the 1967 Trans-Am campaign with the four-barrel induction system producing more horsepower than the competing automakers' eight-barrel systems, for 1968, Chevrolet developed a factory 'cross-ram' aluminum intake-manifold package using two Holley 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 horsepower from to approximately . Chevrolet went so far as to carry the positive crankcase ventilation system (PCV) 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 with little more than the eight-barrel 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.
Another popular service-parts-only component used on the 302 was the magnetic-pulse Delco transistor-ignition ball bearing distributor. Introduced in 1963 on Pontiac's drag racing engines, General Motors fitted it to the 1967 Z/28 before they used it on the L88 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 performance and durability upgrades of its time. Many of the 302s 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 racers like 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 more powerful than the Repco-Holden V8. Weighing, with a iron block and head engine positioned near the car's polar moment of inertia for responsive turn pivoting, a Hewland 5-speed magnesium transaxle, and 10inches wide 13inches front/20inches wide 15inches rear magnesium wheels, it produced incredibly exciting racing. They ran in 2.8 seconds and over .
Reminiscing about the series, mid-70s 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 Mario Andretti, Mark Donohue, David Hobbs, Graham McRae, Brian Redman, Jody Scheckter, and Al and Bobby Unser.
The 3271NaN1 V8, introduced in 1962, had a bore of 4.00in and 3.25in stroke. The exact displacement is 326.72560NaN0. Power ranged from 225to 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, with single Carter 4-barrel, and 360hp, with Rochester fuel-injection. In 1964, horsepower increased to for the newly named L-76 version, and 375hp for the fuel injected L-84, making the L-84 the most powerful naturally aspirated, single-cam, production small-block V8 until the appearance of the, Generation III LS6 in 2001. This block is one of three displacements that underwent a major change in 1968 when the main journal size was increased from 2.3to. 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 No. 151 hydraulic cam.
In 1966, Checker began offering the 327 as an option.[20] The Avanti II and its successors were powered by the 327 and later versions of the small-block V8.
The 327 was fitted in the English Gordon-Keeble. Ninety-nine cars were made between 1964 and 1967. It was also installed in many Isos, until 1972 when General Motors started demanding cash in advance and the Italian manufacturer switched to the Ford Cleveland V8.[21]
In 1968, the 327 L73 developing 250hp was part of the CKD packages exported to Australia from Canada for use in the locally assembled (by General Motors Holdens) Chevrolet Impala and Pontiac Parisienne. GMH used the same specification engine in the Holden HK Monaro GTS327. The engine was used in the Monaro GTS327 to make it the new Holden Muscle Car, and so it could compete in the local improved production (Australian Group C). The car had modified suspension just before release to also be used in local Series Production racing (Australian Group E). A special build 327 was built for GMH for the final run of the HK GTS327 by the Canadian McKinnon Industries. It was a lower compression version of the 1968 engine first used on the HK GTS327, and was dressed as a 1969 engine sporting all 1969 parts. The 327 was replaced in the mid-1969 HT Monaro by the 350 L48 developing 300hp.
The 3501NaN1, with a 3.48inches stroke, first appeared as a high-performance L-48 option for the 1967 Camaro. The exact displacement is 349.850NaN0. One year later, it was made available in that form in the Chevrolet Nova, and in 1969 the lower-compression mainstream LM1 version became an option in the rest of the Chevrolet line. As had been the case with earlier versions of the small-block, the 350 was available in the Beaumont sold by Pontiac Canada, which unlike its U.S. counterparts, used Chevrolet chassis and drivelines. Many variants followed.
Years: 1969–1970
The L46 became an optional engine for the 1969 Chevrolet Corvette. It was a higher-performance version of the base 3501NaN1 V8 with casting number 186, 2.02/ valve heads and had an 11.0:1 compression ratio requiring high octane gas. This produced (SAE gross power) and 380 lb⋅ft (515 N⋅m) torque. It was also available in 1970 with a four-barrel Quadrajet carburetor and L46 hydraulic cam, dome piston (+), 186 heads, and a four-bolt block.
Years: 1967–1980
The L48 is the original 3501NaN1 engine. It was introduced for 1967 in the Super Sport (SS) version of the Camaro (which used it until 1969) and for 1968 in the Chevy II/Nova (which used it until 1979). In 1969, it was used in almost all car lines—Camaros, Caprices, Impalas, El Caminos, Chevelles, and Novas. The 1969 L48s use a hydraulic cam, 4bbl Quadrajet carburetor, cast pistons, 4-bolt main casting number 010 blocks and casting number 041 or 186 heads. Power output was SAE and torque. Compression ratio was 10.25:1. The compression ratio of the L48 was lowered to 8.5:1 in 1971.
In 1972, the L48 (four-barrel V8) option for the Nova was part of the SS package. This is indicated by the fifth digit in the VIN being a K. 1972 was the only year the SS package could be verified by the VIN.
The L48 engine was exported to Australia, where it appeared in the Holden Monaro from 1969 through 1974, and in the Statesman from 1971 through 1974. Towards the end of the HQ series in 1973–74, due to US emissions regulations, the performance of these engines had dropped to the same or lower than Holden's locally manufactured V8, which was not yet subject to similar regulations, so Holden discontinued using the engine.
The L48 V8 was the standard engine in the 1975–1980 Chevrolet Corvette. The L48 V8 Corvette engine produced in 1975. Power increased to in 1976 and stayed the same in 1977. The 1978 saw for California or high altitude areas and everywhere else. Power increased to in 1979 but decreased to in 1980.
The 1970 model year Camaro had a high-performance two-barrel Rochester carburetor. In 1971, it dropped to, and net performance further dropped to for 1972 and for 1973–1976. It was basically the two-barrel version of the L48 350. It was produced until the 1976 model year. It had of torque.
The LM1 was introduced for 1969 model year as a 9.0:1 255 hp engine. It was essentially an L48 engine in all ways except for 75cc combustion chambers rather than the L48's 64cc, and less spark advance to allow it to run on regular-grade fuel. Throughout its lifespan, it used a four-barrel carburetor (usually with a Rochester Quadrajet), mechanical ignition points, and an electronic or computer-controlled spark system. In a lower compression, unleaded gas, considerably more emissions control-hampered form it was rated at SAE net by 1971, and continued the base Chevrolet 350 cu in engine in passenger cars to 1988, optional in most models, standard in some. It was superseded by the L05 powerplant after 1988. This engine was fitted to automatic versions of the 1969 and 1970 Holden Monaro GTS350 in Australia where it was rated at 275 hp most likely due to the use of higher octane fuel and far more spark advance than was fitted to North American versions of the engine.
Years: 1969-1974
The ZQ3 was the standard engine in the 1969–1974 Chevrolet Corvette.
In 1969 and 1970 it was a 300hp version of the 3501NaN1 small-block, with 10.25:1 compression and hydraulic lifters. It used a Rochester "4MV" Quadra-Jet 4-barrel carburetor and a L48 camshaft.[22]
In 1971, power decreased to (gross) and (gross) of torque with a lower 8.5:1 compression. 1972 saw (net) and (net) of torque. In 1973 power decreased to 190hp, but increased slightly in 1974 to 195hp.
Post-1971 blocks possibly 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 were less powerful because of the lower compression ratios used.
Years: 1970–1972
The LT1 was one of the most well-known Chevrolet small-block V8s, becoming available in 1970. It used solid lifters, 11.0:1 compression, the "178" high-performance camshaft, and a 780cuft/min vacuum secondary Holley four-barrel carburetor on a special high-rise aluminum intake, with special 2.5" outlet rams' horn exhaust manifolds in the Corvette, Delco transistor ignition and a low-restriction exhaust factory rated at in the Corvette, and 360hp at 6000 rpm and 380lbft at 4000 rpm in the Camaro Z28[23] (the NHRA rated it at for classification purposes). Redline was 6,500 rpm but power fell off significantly past 6,200 rpm. The LT1 was available in the Corvette and Camaro Z28. Power was down in 1971 to dual-rated (gross)/255hp (net) and of torque with 9.0:1 compression, and again in 1972 (the last year of the LT1, then rated using net only, rather than gross, measurement) to 255hp and .
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 350hp 350 hydraulic-lifter cam, and 9.0:1 compression forged-aluminum pistons producing 250hp (1971 was the first year for SAE net hp rating, as installed in the vehicle with accessories and mufflers) and 285lbft of torque. Its cast-aluminum LT1 valvecovers were painted crinkle-black contrasting with the aluminum manifold and distributor housing. It was down to 205hp and 255lbft of torque for 1975. It produced 210hp in the Corvette for 1976–1977. The 1978 L82 recovered somewhat, producing 220hp and 260lbft in the Corvette and in 1979 it produced 225hp in the Corvette. In 1980, its final year, it produced a peak of 230hp. This engine was also available on the Chevrolet Camaro in 1973 and 1974.
Years: 1981
The L81 was the only 350cuin Corvette engine for 1981. It produced 190hp and 280lbft 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. The L81 was the first Corvette engine to employ a "smart carburetor." The 1980 Rochester Quadrajet was modified to allow electronic mixture control, and an ECM (Engine Control Module) supplied with data from an exhaust oxygen sensor, modified the air–fuel mixture being fed to the engine.
Years: 1969–1986
The LS9 was GM's 350 cubic inch truck engine used in C/K and G-series models up to 8500lb GVWR (gross vehicle weight rating). The LS9 used a Rochester four-barrel carburetor, and its power ratings for 1984 were 165hp at 3800 rpm, and 275lbft torque at 1600 rpm. A version using a closed-loop carburetor was used with the California emissions package in its final years. The LS9 and LT9 engines were replaced for 1987 by the L05 TBI (throttle-body fuel injection) engines. Most of the small-block engines in this timeframe were built at either the Flint engine plant in south Flint, Michigan, or at St. Catharines, Ontario. The Flint plant was producing about 5,200 engines per day in the mid-1980s, and had a slower, separate line for the TPI engines used in the Camaro and Corvette.[24]
Years: 1981–1986[25]
The LT9 served as GM's heavy-duty (over 8500lb GVWR) emissions[26] variant of the 350cuin. It was used in C/K 20/30 pickups, G30 passenger and cargo vans (built in Lordstown, OH, and later in Flint, MI), and P30 chassis used for motorhomes and step vans.
The LT9's listed specifications are 160hp at 3,800 rpm and 250lbft of torque at 2,800 rpm with 8.3:1 compression.[27] LT9 engines were carbureted with Rochester Quadrajets from the factory and generally have four-bolt mains. The LT9 is often known as the "M-code 350," from the eighth character of the VIN.
Years: 1982 and 1984
The 1982 L83 was again the only Corvette engine, producing 200hp and 285lbft of torque from 9.0:1 compression. Since GM did not assign a 1983 model year to production Corvettes, there was no L83 for 1983. This was also the only engine on the 1984 Corvette, at 205hp and 290lbft of torque. The L83 added "Cross-Fire" fuel injection (twin throttle-body fuel injection).
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 230hp for 1985–1986, 240hp for 1987-1989 (245hp with 3.08:1 rear axle ratio (1988-1989 only)), and 245hp in 1990–1991 (250hp with 3.08:1 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 until 2015 when the ZZ6 received the fast burn heads). The L98 V8 was optional on January 1987–1992 Chevrolet Camaro and Pontiac Firebird models (rated at 2250NaN0-2450NaN0 and 3300NaN0–3450NaN0)The 1987 versions had 200NaN0 and 150NaN0 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.
Vehicles using the L98:
The L05 was introduced in 1987 for use in Chevrolet/GMC trucks in 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 (including chassis cabs and four-door crew cabs). The L05 was also used in the G-van models and the P30 step vans, as well as in 9C1-optioned police package Caprices, and in the following other vehicles:
L05s 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 L05s used with the trucks and 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 and D-bodies until production ceased in 1996.
A single belt (serpentine belt) accessory drive was introduced on the L05, the 5.0L L03, and the 4.3L V6 LB4 engines used in the 1988 GMT400 models, but not on the older R/V models (R/V models received the serpentine belt drive in 1989 when the front grille was facelifted in appearance to the GMT400 lineup). In mid-1996, the L05 was equipped with heads used in the 1996 G30. In February 2008, a Wisconsin businessman reported that his 1991 Chevrolet C1500 pickup had logged over 1 million miles without any major repairs to its L05 engine.[14] The article also mentioned that the Flint engine plant that built the engine, had produced 45 million engines in its 45-year history, before closing in 1999.
The Vortec 5700 L31 (VIN code "R") is a 5.7L V8 truck engine. It is Chevrolet's last production first-generation small-block. The cylinder heads feature combustion chambers and intake ports very similar to those of the LT1 V8, but lacking the LT1's reverse-flow cooling and higher compression. As such, the L31 head is compatible with all older small-blocks, and is a very popular upgrade. It offers the airflow of more expensive heads, at a much lower cost. It does, however, require a specific intake manifold (the L31 has four bolts per head attaching the intake manifold, as opposed to the "traditional" six bolts per head found on older Chevrolet small-blocks). Chevrolet's L31 was replaced by GM's LS-based 5.3L LM7 and 6.0L LQ4. Depending on components and computer module the Vortec 5700 produces 2550NaN0 to 3500NaN0 at 4600 rpm and 3300NaN0 to 3500NaN0 of torque at 2800 rpm. Known as the GEN 1+, the final incarnation of the 1950s-vintage small-block ended production in 2003. It is still in current production as a crate engine for marine applications and automotive hobbyists as the 'RamJet 350' with minor modifications. Volvo Penta and Mercury Marine also still produce the L31. The "Marine" intake, despite its cast iron construction, is an L31 upgrade that allows use of common Bosch-style injectors with various flow rates while still maintaining emission compliance.
TBI L31 applications:
Special applications:
The 400.920NaN0 400 is the only engine in this family; it was introduced in 1970 and produced for ten years. It has a 4.1251NaN1 bore and a 3.752NaN2 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. The 400 is the only engine that uses a 2.651NaN1 main bearing journal and a 2.11NaN1 rod bearing journal. The connecting rod was also 400 specific being 5.5651NaN1 as opposed to the 5.71NaN1 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 1979. The 400 can have either 2 or 3 frost-plugs per side though all 400 blocks have the provisions for a 3rd frost-plug on each side.
The 400 was rated at 245– gross (150– SAE 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 265hp with a two-barrel carburetor. All 400s came with a two-barrel carburetor until 1973. A four-barrel carburetor option became available in 1974.
The 400 was never intended as a high-performance engine and never saw large factory horsepower numbers; nevertheless, it developed a reputation for creating considerable torque for its horsepower (up to 4000NaN0 in 1970) and has since become popular for many types of racing, both on- and off-road. It was also used for the limited production Avanti for a few years in the 1970s.
The 1975–1976 262 was a 90° pushrod V8 with an iron block and heads. Bore and stroke were . Power output for 1975 was 1100NaN0 at 3600 rpm and 1950NaN0 at 2000 rpm. The 262 was replaced with the 305 for the 1977 model year.
This was Chevrolet's second 4.3L power plant; four other Chevrolet engines displaced 4.3L: the Vortec 4300 (a V6 based on the Chevrolet 3501NaN1, with two cylinders removed), the original 2651NaN1 V8 in 1954, a bored version of the stovebolt-era 235 inline six displacing 2611NaN1, and a derivative of the Generation II LT engines known as the L99 (using the 305's 3.7361NaN1 bore, 5.941NaN1-long connecting rods, and a 31NaN1 stroke).
This engine was used in the following cars:
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. Introduced in 1976 models, it had a displacement of 3051NaN1. It was intended to fill the gap where the venerable 283 and 307 had been. Bore and stroke were 3.736x, using 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 and 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 1980s, the 305 became General Motors' most common V8, followed closely by Oldsmobile's 307. The 305 also became the standard V8 in GM's C/K truck series, and was even used in the Corvette for California in 1980.
Crankshafts used with the 305 had the same casting number as the 350 with one discernible difference—the 305 crank is lighter in weight to compensate for engine balancing. As a result, the counterweights are smaller, 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 31NaN1 stroke using 5.941NaN1 connecting rods, into the Generation II LT engine L99 263.
From 1976 onward into the early 1980s, these engines were prone to wearing out their camshaft lobes prematurely due to a combination of improper manufacturing and poor quality controls (a result of GM's cost-cutting measures). The 305 is sometimes dismissed in performance circles because of its lackluster performance, small bore size, and difficulty flowing large volumes of air at high RPM. However, two variants of the 1983 to 1992 305 were notable performers: the 1983–1988 L69 High Output 5.0L (only used in late 1983–early 1986 F-body and late 1983–1988 Monte Carlo SS) and the 1985–1992 LB9 Tuned Port Injection 5.0L (F-body only).
After 1993, its usage was limited to light trucks and SUVs until the 1999 model year while vans and commercial vehicles continued until 2002. 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. The cylinder block is still in production by GM (part number 10243869) for Sprint Car Spec Racing.[29]
The first iteration of the 305, the LG3 was introduced in 1976. This variant used a Rochester 2GC carburetor from 1976 to 1978. In 1979, the more fuel-efficient Rochester Dual-Jet two-barrel carburetor replaced the older 2GC. This change also resulted in a drop in power to 1300NaN0 and 125hp for California emissions cars. All years had an 8.5:1 compression ratio. It was discontinued in 1982.
The LG4 produced NaN0NaN0 and NaN0NaN0. Introduced in 1978, the LG4 was essentially an LG3 with the addition of a four-barrel carburetor and larger valves. The engine saw a series of gradual improvements, increasing reliability, fuel economy, 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 (except Canadian models). The CCC system included the electronic Rochester 4-bbl E4ME Quadra-Jet, with computer-adjusted fuel metering on the primary venturis and a throttle position sensor allowing the CCC to calculate engine load. In the ignition system, CCC was fully responsible for the timing curve; mechanical and vacuum advances were eliminated from the distributor. The more precise spark timing provided by the CCC made possible a series of increases in compression ratio from a pre-CCC 8.4:1, to 8.6:1, to a knock-sensor–assisted 9.5:1, all while still only requiring 87 AKI regular unleaded fuel.
In 1983, Chevrolet replaced the cast-iron intake with an aluminum version and used either 14014416 ("416") or 14022601 ("601") heads with 1.84 inch intake valves, 1.50 inch exhaust valves, 58 cc chambers, and 178 cc runners. For 1985, the 4-valve-relief, flat top pistons from the L69 were added to the LG4, which resulted in another 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 1985 models to 1650NaN0 from the 1500NaN0 rating in 1984. For 1986, Chevrolet changed over to a one-piece rear main seal engine block design to minimize leaks and warranty claims; however, some early 1986 blocks retained a two-piece rear main seal.
For 1987, Chevrolet once again made some revisions to increase overall reliability, many of them borrowed from the TBI L03, which was to replace the LG4. The coil-in-cap HEI distributor was retired, and an all-new electronic distributor design 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° instead of 90° 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 Corvette were the first to have the centerbolt valve covers). Another improvement was use of a hydraulic lifter/roller camshaft on most 1987 LG4s. Some early engines have lifter retainer provisions, but use 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.
Years: 1982–1984
The LU5 "Crossfire EFI 5.0L" featured a dual Throttle Body Injection set-up, based upon the original "Crossfire 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 used 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 from 1982 to 1984. Since it was 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. These problems were compounded by 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.
Years: late 1983–1988
The L69 High Output 5.0L was released late into the 1983 model year. It was optional in the Firebird Trans Am, Camaro Z28, and IROC-Z, and was standard in the revived Monte Carlo Super Sport.
The L69 features a compression ratio of 9.5:1 and a relatively aggressive stock camshaft. It also uses a performance-tuned CCC ECM/PROM, a knock sensor, a performance-tuned E4ME 750cuft/min Rochester Quadra-Jet 4 barrel carburetor, and a special, free-flowing exhaust system with large diameter exhaust manifolds, Y-pipe and catalytic converter.
The L69 F-body exhaust system components would be revised slightly and used again on the later LB9 305 and L98 350 TPI engines. Additionally, the engines came equipped with a functional cold air induction hood on the 1983-1984 Trans Am, a dual snorkel air cleaner assembly on the 1983-1986 Camaro Z28 and IROC-Z and 1985-1986 Trans Am, a large, single snorkel on the 1983-1988 Monte Carlo SS (also, rare optional dual snorkel in 1987-1988), an aluminum intake manifold, high stall torque converter on the Monte Carlo SS and 1984 F-bodies, or a lightweight flywheel on T-5 equipped F-bodies.
The L69 engine produced at 4800 and of torque at 3200 rpm in the F-Body and was rated at in the Monte SS.[30] [31]
Years: 1981–1986
The LE9 was a version of the 305 with a four-barrel carburetor, a 9.5:1 compression ratio, the LM1 cam and 14010201 casting heads featuring 1.84/1.50" valves, and chambers. The engine produced at 4,400 and at 2,000 rpm.
Years: 1985–1992
The LB9 "Tuned Port Injection 5.0L" was introduced in 1985. At its core was the stout L69 shortblock and it used 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 Z28, IROC-Z and Trans Am equipped with the WS6 performance suspension. The LB9 was also available in the '87-92 GTA and Firebird Formula.2150NaN0 and 2750NaN0 and varied between NaN0NaN0 (with NaN0NaN0 of torque) over the years offered.
Years: 1987–95
The L03 produced 1700NaN0 at 4400 rpm and of torque at 2400 rpm in 1993–1995 GM trucks. This engine used the TBI throttle body fuel injection, which was a hybrid between EFI and carburetor technology. It used an EFI system with electronically controlled injectors, which were mated to a twin barrel "carburetor" body. It featured "swirl port" heads (helped emissions, but severely stunted power output) and served as the base V8 engine in all C/K 1500 Series and 2500 Series (under 8,500 lbs GVWR) GMC/Chevrolet trucks and vans. It was also very common in Firebirds and Camaros because it was the only engine that offered a five-speed manual combination. The 350 exceeded the Borg-Warner T5's input power ratings, and as such, it was cut from the 350 cars to prevent lemon law and warranty losses.
The L03 used hydraulic roller lifters, which allowed it to recover some of the lost horsepower from its factory design, while further increasing efficiency (reduced rotational drag). Despite downfalls in its aspiration restrictions, the L03 was known for its reliability (1987–1990 F-bodies with the L03 did not use a rev limiter). The L03 used dished pistons with a 9.3:1 to 9.5:1 compression ratio. The L03 TBI featured a 3.736" bore and 3.48" stroke, the same as its TPI cousin, the LB9.
Years: 1996–2002
The Vortec 5000 L30 is a V8 truck engine, displacing 5,020 cc (305.4 cubic inches). Bore is 951NaN1 and stroke is 88.41NaN1. The compression ratio is 9.1:1.[32] It was replaced by the 4.8 L Vortec 4800 LR4 for the 1999 Chevrolet Silverado/GMC Sierra trucks and 2003 Express/Savana vans. In C/K trucks, the 5000 produces 2300NaN0 net flywheel at 4600 rpm and 2850NaN0 net flywheel torque at 2,800 rpm. In vans, it produces 2200NaN0 net flywheel at 4600 rpm and 2900NaN0 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:
The 267 was introduced in 1979 for the GM F-body (Camaro), G-body (Chevrolet Monte Carlo, El Camino), A-body (Malibu Classic, 1979–1981) and also used on GM B-body cars (Impala and Caprice models). The 4389cc engine had the 350's crankshaft stroke of 3.481NaN1 and the smallest bore of any small-block, 3.51NaN1, shared with the 200 V6 introduced a year earlier.
It was only available with a M2ME 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.[33]
While similar in displacement to the other NaNCID 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 3051NaN1 as their base V8 engine.
The 267, when introduced in the GM F-Body as the L39 4.4L, made 120hp at 3600 rpm and 215lbft of torque at 2000 rpm (SAE net). Power output would drop in subsequent years of the engine. The 2671NaN1 had a low 8.3:1 compression ratio.[34]
The original design of the small-block remained remarkably unchanged for its production run, which began in 1954 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:
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.
| Gen I | Years | Engine option code (VIN identifier) | Power hp (kW) | Torque lb-ft (Nm) | Displacement c.i. (cc) | Fuel (octane) | Bore x Stroke in (mm) | Compression ratio | Block & heads (iron or aluminum) | width=320 | Block features |
|---|---|---|---|---|---|---|---|---|---|---|---|
| I | 1967-69 | Z28 | at 5800 | at 4200 | 100+ | 11.0:1 | Iron | only Camaro Z/28, 1968 Cross-Ram intake-manifold with 2 Holley 4bbl | |||
| I | 1996-02 | L30 (M) | at 4600 | at 2800 | 9.1:1 | Iron | Truck/van only | ||||
| I | 1987-95 | L03 (E/H) | at 4400 | at 2400 | 9.1:1 | Iron | TBI; passenger car used roller cam | ||||
| I | 1988-96 | L05 (K) | at 4400 | at 2800 | 9.3:1 | Iron | TBI; 9C1 optioned Caprice and F-bodies had hydraulic roller cam | ||||
| I | 1978-88 | LG4 (F/H) | at 4600 | at 2800 | 8.6:1 | Iron | 4bbl Quadrajet | ||||
| I | 1981-86 | LE9 (F) | at 4400 | at 2000 | 9.5:1 | Iron | Truck/Van only - electronic spark control module used | ||||
| I | 1982-83 | LU5 | Iron | "Crossfire EFI 5.0L" | |||||||
| I | 1968-73 | L14 | at 4600 | at 2400 | 9.0:1 | Iron | |||||
| I | 1967-80 | L48 (K) | 8.25-10.5:1 | Iron | |||||||
| I | 1969-70 | L46 | 100+ | 11.0:1 | Iron | Corvette only | |||||
| I | 1969-76 | L65 | 87 | 8.5:1 | Iron | 2bbl | |||||
| I | 1969-88 | LM1 (L) | Iron | 4bbl Rochester Quadrajet (4MV, M4MC, E4ME); retail option until 1981 when last used with the Camaro Z28; post-1980 use of the LM1 was for 9C1-optioned B (Caprice, Impala) and G-bodies (Malibu) | |||||||
| I | 1970-74 | ZQ3 | at 3500 | 8.5-10.25:1 | Iron | 4bbl, Corvette. L48 camshaft | |||||
| I | 1970-72 | LT1 | at 6000 | at 4000 | 9.1:1 | Iron | 4bbl | ||||
| II | 1992-97 | LT1 (P) | at 4800-5200 | at 2400-3400 | 87 or 91 | 10.4:1 | Iron for B & D bodies Aluminum for F and Y bodies | Reverse cooling | |||
| I | 1973-80 | L82 | 9:1 | Iron | 4bbl Rochester Quadrajet; flat top pistons with a D-shaped relief cut for valve clearance | ||||||
| I | 1981 | L81 | 8.2:1 | Iron | 4bbl Rochester Quadrajet (E4ME), Corvette | ||||||
| I | 1970-86 | LS9 (L) | at 3800 | at 1600 | 8.2:1 | Iron | 4bbl, truck | ||||
| I | 1981-86 | LT9 (M) | at 3800 | at 2800 | 8.3:1 | Iron | 4bbl, truck | ||||
| I | 1982-84 | L83 | 9.0:1 | Iron | CrossFire | ||||||
| I | 1985-92 | L98 (8) | at 4000 | at 3200 | 9.5-10:1 | Iron/Aluminum (Corvette) | TPI | ||||
| I | 1996-02 | L31 (R) | at 4600 | at 2800 | Iron | truck, Vortec | |||||
| I | 1970-80 | 4.125 in × 3.75 in (104.8 mm × 95.3 mm) | Iron | 1970-72 4-bolt main, 1973–80 2-bolt main | |||||||
| I | 1975-76 | at 3600 | Iron | Nova and Monza only; 2bbl Rochester 2GC carburetor | |||||||
| II | 1994-96 | L99 (W) | Iron | reverse cooling, Chevy Caprice sedans ONLY, including police vehicles | |||||||
| I | 1983-88 | L69 (G) | at 4800 | at 3200 | 9.5:1 | Iron | H.O., Firebird/Camaro, Monte Carlo SS only | ||||
| I | 1985-92 | LB9 (F) | Iron | TPI, Firebird/Camaro only | |||||||
| I | 1976-82 | LG3 (U) | at 4400 | at 2400 | 8.5:1 | Iron | 2bbl | ||||
| Generation II | |
| Manufacturer: | General Motors |
| Aka: | GM LT engine |
| Production: | 1991-1997[35] [36] |
| Predecessor: | Generation I |
| Successor: | Generation III |
| Configuration: | Naturally aspirated 90° V8 |
| Block: | Aluminum, Cast iron |
| Head: | Aluminum, Cast iron |
| Valvetrain: | Pushrod, 1.5:1 ratio rocker arms; 2 valves per cylinder |
| Oilsystem: | Wet sump |
| Coolingsystem: | Water-cooled |
General Motors' Generation II LT1 is a small-block V8 engine. Making its debut in the 1992 Chevrolet Corvette, the new LT1 sought to draw upon the heritage of the 1970 Chevrolet LT1.
A significant improvement over the original Generation I V8 is the Generation II LT1'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/flex-plate) one piece rear main seal housing, oil pan and valve cover gaskets and valvetrain assembly (not including timing set, which includes a gear to drive the water pump). The LT1 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.
In 1991, GM created a new-generation small-block engine called the "LT1 350", distinct from the high-output Generation I LT1 of the 1970s. It displaced 350cuin, and was a 2-valve pushrod design. The LT1 used a reverse-flow cooling system which cooled the cylinder heads first, maintaining lower combustion chamber 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 1992–93 LT1s used speed density fuel management, batch-fire fuel injection and a dedicated Engine Control Module (ECM). In 1994 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 ECM held its calibration information in a replaceable PROM chip, the 1994-95 OBD1 PCMs are reprogrammable through the diagnostic port.
The early Optispark distributor had durability problems, and a revised version was introduced on the 1994 B- and D-bodies and on the 1995 Y- and F-bodies. Changes include a vacuum port to draw filtered air through the distributor to remove moisture and ozone and a revised drive system which uses an extended dowel pin on the camshaft rather than a separate splined shaft in the camshaft gear. 1996 saw major revisions for OBD-II: a second catalytic converter on the F-body cars, rear oxygen sensors to monitor catalyst efficiency, and a new engine front cover with a crankshaft position sensor. Some OBD-II features had been added to the Corvette starting in 1994 for testing purposes. 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 LT1s in Y-body Corvettes were factory rated at 300-1NaN-1 and 3300NaN0. 1996 LT1 Corvettes were rated at 300-1NaN-1 and 3400NaN0.
The 1993–95 F-bodies were rated at 275hp and 3250NaN0, while the 96–97 cars were rated at 2850NaN0 and 3350NaN0. The 96–97 WS6 and SS F-bodies were rated at 3050NaN0.
The 1994–96 B- and D-bodies were rated at 260hp and 3300NaN0 (250hp with V08 mechanical fan as part of V92 or V4P towing option groups).
The LT4 was the special high-performance version of the new-generation LT1. It featured a slightly more aggressive camshaft profile, 1.6:1 aluminum roller rocker arms, lighter hollow intake valves and liquid-sodium filled exhaust valves, larger fuel injectors, performance crankshaft, higher 10.8:1 compression ratio and high-flow intake manifold (painted red) with extra material above the port available to allow port matching to the raised port LT4 cylinder heads. The LT4 was conservatively underrated at 3300NaN0 and 3400NaN0. 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 1997 SLP Camaros SS and SLP Firehawks with 6-speed manual transmissions.
The LT4 was available on the following vehicles:
All 135 production engines for the Firehawks and SSs were completely disassembled, balanced, blueprinted and honed with stress plates. One in 5 engines was tested on a Superflow engine dyno. Every car was tested on a chassis dyno and then performed a 60NaN0 road test.
For model year 1990, Chevrolet released the Corvette ZR-1 with the radical Lotus Engineering-designed double overhead cam LT5 engine. Engineered in the UK but produced and assembled in Stillwater, Oklahoma by specialty engine builder Mercury Marine, the all-aluminum LT5 shared only the 4.4 inch bore spacing with any previous Chevy small-block engine. It does not have reverse cooling and is generally not considered a small-block Chevrolet.
Used only in Corvettes,[37] the LT5 was the work of a team headed by Design manager David Whitehead, and was hand built by one headed by project engineer Terry D. Stinson.[38] It displaced 5727cc and had a bore x stroke NaNmm instead of the usual NaN1NaN1 and featured Lotus-designed DOHC 4 valves per cylinder rather than the usual Chevrolet 16-Valve OHV Heads. The preproduction LT5 initially produced 385hp, but was reduced to 375hp and 3700NaN0 for the 1990-1992 Corvette ZR-1. The power ratings jumped to 4050NaN0 at 5800 rpm and 3850NaN0 of torque at 5200 rpm from 1993 until its final year in 1995,[39] 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.
A second generation of the LT5 was in the testing phase as early as 1993. What little information survived showed that it would have used a dual plenum system similar to the first generation Dodge Viper as well as variable valve timing. The next generation LT5 was set to produce between 450hp and 475hp. 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 beginning model year 1993. Engines that were to be installed in the as yet unbuilt ZR-1's were sealed and crated for long-term storage. After they were built at the Mercruiser plant in Stillwater, Oklahoma they were shipped to Bowling Green, Kentucky and stored in the Corvette assembly plant until the 1994 and 1995 ZR-1s went down the assembly line. A total of 6,939 cars were produced.[40] The LT5 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.[41] GM also took lessons learned from producing a completely aluminum engine and applied them to the new LS series of engines.
The LT5 was available on the following vehicles:
The L99 V8, produced from 1994–1996, shared a 3.7361NaN1 cylinder bore with the 3051NaN1 but had a 31NaN1 stroke compared to 3.481NaN1 of the 3051NaN1.[42] The pistons used in the 4.3 L V8 were the same as the Vortec 5000's, but longer 5.941NaN1 connecting rods were used to compensate for the shorter stroke. The L99 featured updated Generation II block architecture, and is externally identical to the larger 5.7 L LT1 Generation II V8. Like the LT1, it features sequential fuel injection, reverse-flow cooling with a cam-driven water pump, and an optical ignition pickup. Output is and 2450NaN0.
The L99 4.3 L V8 was the base engine in 1994-1996 Chevrolet Caprice sedans, including 9C1 police package sedans, and was not available in any other vehicles. The L99's smaller displacement provided slightly better EPA fuel economy than the 5.7 L LT1, but at significantly reduced horsepower and torque levels.
The LT6 and LT7 are not actually part of the LT family. See Oldsmobile Diesel engine for more information.