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Chevrolet Small-Block engine
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Chevrolet's small-block V8 is a not a single engine but a series of famous automobile engines built on the same basic small (for a V-8) engine block. Retroactively referred to as the "Generation I" small-block, it is distinct from subsequent GM "Generation II" LT and "Generation III" LE engines.
Production of the original small-block began in 1955 with a displacement of 265 ci., growing incrementally over time until reaching a full in 1970.
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Encyclopedia
Chevrolet's small-block V8 is a not a single engine but a series of famous automobile engines built on the same basic small (for a V-8) engine block. Retroactively referred to as the "Generation I" small-block, it is distinct from subsequent GM "Generation II" LT and "Generation III" LE engines.
Production of the original small-block began in 1955 with a displacement of 265 ci., growing incrementally over time until reaching a full in 1970. Along the way several famous intermediate displacements appeared, such as a with mechanical fuel-injection that produced a then milestone one horsepower per cubic inch, and an even more powerful per cubic inch 327, but none caught on like the variant. Introduced as a performance engine in 1967, the 350 went on to be employed in high and low output variants across the entire Chevrolet product line.
Although all four of Chevrolet's General Motors siblings of the period designed their own V8s, the Chevrolet 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Finally superseded by GM's Generation II LT and Generation III V8 in the early 2000s and discontinued in 2004, the engine is still made by a GM subsidiary in Mexico as an aftermarket replacement. In all, over 90,000,000 small-blocks have been built in carbureted and fuel injected forms since 1955.
The small-block family line was honored as one of the 10 Best Engines of the 20th Century by automotive magazine Ward's AutoWorld.
Confusion with LT and LE engines
The original Chevrolet-designed small-block is a specific family of engines manufacturerd originally in 1955 and installed as production powerplants by GM for 48 years.
Subsequent GM small block V-8 engine designs built on different blocks are often confused with the original small-block.
- For more information on the Generation II small-block V8s, which differ mainly in their reverse-flow cooling system, see the GM LT engine.
- For more information on the current family of Generation III/IV General Motors small-block V8s see the GM LS engine.
Overview
The first generation of Chevrolet small-blocks began with the 1955 Chevrolet V8 offered in the Corvette and Bel Air. Soon after being introduced, it quickly gained popularity among stock car racers, becoming known as the "Mighty Mouse" motor, after the popular cartoon character of the time.
By 1957 it had grown to . Fitted with the optional Rochester mechanical fuel injection, it became one of the first production engines ever to make one horsepower per cubic inch. The 283 would later be extended to other Chevrolet models, replacing the old style 265 V8s.
A high-performance variant followed, turning out as much as 375 hp and increasing horsepower per cubic inch to 1.15.
It was, however, the series that came to the best known Chevrolet small block. The engine's oversquare 4.00-inch bore and 3.48-inch stroke (102 mm by 88 mm) are nearly identical to the LS3 engine of today, but much has changed. Installed in everything from station wagons to sports cars, in commercial vehicles, and even in boats and (in highly modified form) airplanes, it is by far the most widely used small-block of all-time.
Though not offered in GM vehicles since 2004, it is still in production today at General Motors' Toluca, Mexico plant under the company's "Mr Goodwrench" brand.
From 1955-74, the small-block engine was known as the "Turbo-Fire V8".
Chevrolet tested the small-block twice with no water and no oil at wide-open throttle. The first time it lasted an hour and 15 minutes and the second time it lasted two hours.
Original small-blocks
The small-block made its debut in 1955 and remained popular for over five decades for its relatively compact size, light weight, and extensive aftermarket support. Chronologically, the original series of small-blocks include:
265
The 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 in-line six, the 2-barrel debut version went from drawings to production in just 15 weeks.
A pushrod cast-iron engine with hydraulic lifters, the small block was available with an optional 4-barrel Rochester carburetor, increasing engine output to . The oversquare (3.75 in (95 mm) bore, 3 in (76 mm) stroke) engine's 4.4 in (111.8 mm) bore spacing would continue in use for decades.
Also available in the Bel Air sedan, the basic passenger car version produced with a 2-barrel carburetor. Upgraded to a four-barrel Rochester, dual exhaust "Power Pack" version, the engine was conservatively rated at .
A shortcoming of the 1955 265 was that the engine had no provision for oil filtration built into the block, instead relying on an add-on filter mounted on the thermostat housing. In spite of its novel green-sand foundry construction, the '55 block's 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 carb, with twin 4-barrels, and with twin fours and a high-lift cam.
283
The 265 ci V-8 was bored out to 3.87 in (98 mm) in 1957, giving it a displacement. Five different versions between and were available, depending on whether a single carb, twin carbs, or fuel injection was used. Power was up a bit each year for 1958, 1959, and 1960.
The 1957 Ramjet mechanical fuel injection version produced an even per cubic inch, an impressive feat at the time. By 1961, a prolific was generated by this unit.
327
The V8, introduced in 1962, had a bore and stroke of 4 in (102 mm) by 3.25 in. Power ranged from L30 to 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-brl, and , with Rochester mechanical fuel injection. In 1964, horsepower increased to for the now dubbed L76 version, and for the fuel injected L84 respectively, making the L84 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 under went a major change in 1968/1969 when the main bearing size was increased from .
350
The 350 first appeared as a high-performance 295 hp L48 option for the 1967 Chevrolet Camaro. A year later it was made available in the Nova, in 1969 the balance of the Chevrolet line. Many variants followed:
Years: 1967-1980
The L-48 is the original , available only in the Camaro or Chevy II/Nova in '67 & '68. In '69 it was used in almost everything; Camaros, Corvettes, Impalas, Chevelles & Novas. From '75-'80 it was available only in the Corvette. L-48's use a Hyd Cam, 4bbl Qjet, Cast pistons, 2 bolt main caps, "Pink" Rods, #0014 Blocks & #993 heads. Power output ranges from 300HP(gross) down to 175HP(net).
The L48 was the standard engine in the 1971 Chevrolet Corvette. It produced and with an 8.5:1 compression ratio.
The 1976-1979 L48 was the standard Corvette engine and produced and . The 1980 L48 stood at and from 8.2:1 compression.
In 1972 the only way to get a L48 (4bbl V8) in a Chevy Nova was to get the Super Sport Package. This is indicated by the 5th digit in the VIN being a "K". 1972 was the only year you could verify the Super Sport package by the VIN.
In 1973 the "L-48" had cold air induction (throttle activated) and developed (net). Beginning in 1974 the hp was reduced for several years until it reached a low of (net) in 1975, before rising again.
Years: 1969, 1970, 1972-1975
The ZQ3 was the standard engine in the 1969-1970 Chevrolet Corvette. It was a version of the small-block, with 10.25:1 compression and hydraulic lifters. It used a Rochester "4MV" Quadra-Jet 4-barrel carburetor. This was the first block produced that featured the larger 2.45 inch main bearing versus the older 2.30 inch main bearing in 1968/1969.
The 1969 ZQ3 produced and with 8.5:1 compression, dropping another in 1973. 1975 saw the ZQ3 at and .
Years: 1969, 1970
The L46 was an optional engine on the 1969-1970 Chevrolet Corvette. It was a , version of the ZQ3 with higher 11:1 compression.
Years: 1970-1972
The LT-1 was the ultimate V8, becoming available in 1970. It used solid lifters, 11:1 compression, a high-performance camshaft, and a Holley four-barrel carburetor on a special aluminum intake to produce and . It was available on the Corvette and Camaro Z28. Power was down in 1971 to and with 9:1 compression, and again in 1972 (the last year of the LT-1, now rated using net, rather than gross, measurement) to and .
The "LT1" designation was later reused on a Generation II GM engine, the LT1.
302
Chevrolet produced a special engine for Trans Am racing from 1967-1969. It was the product of placing the 3-inch stroke crankshaft into a 4-inch bore block. Although the 283 also used a 3-inch stroke crankshaft, it was a low performance cast iron crankshaft. The crankshaft for the 302 was specially built of forged steel. This engine was used only in the first-generation Camaro Z28. Conservatively rated at 290 hp (216 kW), actual output was around . This block is one of 3 displacements that underwent a transformation for the 1968/1969 period when the main bearing size was increased from 2.30 in to 2.45 in.
A letter from G.D. Thompson, Chevrolet Engineering Laboratory, dated June 5, 1967 to D.A. Martens, Engineering Department, subject Z-28 Service Pack Power Breakdown states "engine capable of 448 HP will deliver 432HP in full vehicle dress" .... "as installed data corrected to 100 degree brake and 29.52hg dry barometer yields a maximum of 403.8 HP. This correction more closely represents what is available when installed in a vehicle" *bhp@7400rpm
307
A version was produced from 1968 through 1973. Engine bore was 3.875 inches (98.4 mm) with a stroke.
The 307 replaced the 283 in Chevrolet cars and produced 200 hp (149 kW) SAE gross at 4600 rpm and of torque at 2400 rpm in the 1960s. The later emissions-modified versions produced just 115 hp (86 kW) SAE net, giving the engine one of the lowest power-per-displacement ratings of all time. Chevrolet never produced a high-performance version of this engine, though they did produce, for Outboard Marine Corporation, a high-performance marinized 307, rated at and SAE gross, depending on year, that shipped with the Corvette/Z-28's cast aluminum valve covers and Rochester QuadraJet carb. Chevy also built other versions of the OMC 307 rated at , and SAE gross.
400
A small-block was introduced in 1970 and produced for 10 years. It had a bore and a stroke. Initial output was and was only available equipped with a 2-barrel carburetor. In 1974 a 4-barrel version of the 400 was introduced,while the 2-barrel version stopped production in 1975. 1976 was the last year that the 400 was used in a Chevrolet Passenger car, available in both the A-Body and B-Body line. While popular with circle-track racers, the engine was prone to cooling troubles if cylinder heads without steam holes were used. They mostly put out 250 hp stock. Due to the way the block was designed, the 2 bolt main engines were stronger than the 4 bolt versions. The 509 2 bolt main block is the most desirable 400 block.
Later Small Blocks
Multiple variations of the original small-block were introduced after 1970's bore-out to 400 cubic inches, many based on the already much modified 350 design. Chronologically, they include:
350 variants
Years: 1973-1980
The 1973-1974 L82 was a "performance" version of the 350 producing and from 9:1 compression. It was down to and for 1975. It was the optional engine again in 1976-1977, producing more. The 1978 L82 recovered somewhat, producing and , and then and more for 1979. 1980 saw yet another and .
Years: 1981
The L81 was the only Corvette engine for 1981. It produced and from 8.2:1 compression, exactly the same as the 1980 L48, but added computer control spark advance, replacing the vacuum advance.
Years: 1982, 1984
The 1982 L83 was again the only Corvette engine (and only available with an automatic transmission) producing and from 9:1 compression. This was again the only engine on the new 1984 Vette, at and . 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.
- For the new Generation IV V8, see GM L98.
Years: 1985-1992
The new 1985 L98 added tuned-port fuel injection "TPI", which produced and . It was standard on all 1985-1991 Corvettes (rated at - and -). Optional on 87-92 Chevrolet Camaro & Pontiac Firebird models (rated at - and -)
1987 versions had and more thanks to 9.5:1 compression and a change to hydraulic roller camshaft. Compression was up again in 1991 to 10:1 but output stayed the same.
The LM1 is the base with a 4-barrel carburetor (usually with a Rochester Quadrajet) in passenger cars until 1988. Throughout its lifespan, it received either a points, electronic, and/or computer-controlled spark system, to conventional and feedback carburetors.
LM1s were superseded with the LO5 powerplant after 1988.
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 1996 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:
L05 usage was replaced by the GM LT1 after 1993 in GM B-Bodies until production ceased in 1996.
In mid 1996 the L05 was equipped with Vortec heads used in the 1996 G30.
The L31 replaced the LO5 in 1996 - known as the Vortec 5700. Known as the GEN 1+, this was the final incarnation of the 1955-vintage small block, ending production in 2005 with the last vehicle being a Kodiak/Topkick HD truck. Volvo Penta and Mercury Marine still produces the L31. The "MARINE" intake is a potential upgrade for L31 trucks.
The GM Goodwrench 350 crate engine comes in several variations. The lowest priced uses the pre-1986 four-bolt casting molds with two dipstick locations; pre-1980 on the driver's side and post-1980 on the passenger's side. This engine was produced in Mexico since 1981 as the Targetmaster 350, and now the GM Goodwrench 350.
262
The 1975-1976 262 was a 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 and . The 262 was underpowered and was replaced by the 305 the following year.
This was Chevrolet's second 4.3 L-displacement powerplant; two other Chevrolet engines displaced 4.3 L: the Vortec 4300 (a V6 based on the Chevrolet 350, with two cylinders removed), and a derivative of the LT1 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:
305
The 305 variant of the small-block Chevrolet introduced in 1975 had a displacement of with a 3.736-inch (95 mm) bore and 3.48-inch (88.4 mm) stroke. The 262 was considered underpowered for use in vehicles with a wheelbase greater than 110 inches, so GM engineers decided to increase the bore diameter from and increase the stroke from (from the 350). Some performance enthusiasts have noted a marked resistance to performance upgrades on the 305 because of its small bore, poor selection of aftermarket cylinder heads, and the relatively high availability of engines.
Induction systems for the 305 included carburetors (both 2 and 4-barrel), throttle-body injection (TBI), tuned-port fuel injection (TPI), and sequential fuel injection (GM Vortec).
The 305 was used in the following cars:
After 1996, its usage was limited to light trucks and SUVs as the Vortec 5000.
| Year | hp (kW) | lb·ft (N·m) |
|---|
| 1976 | 140 | 250 | w/2bbl. | | 1977 | 145 | 245 | w/2bbl. | | 1978 | 140 | 240 | w/2bbl. | | 1978 | 160 | 235 | w/4bbl. | | 1979 | 130 | 245 | w/2bbl. | | 1979† | 125 | 235 | w/2bbl. | | 1980 | 155 | 240 | w/4bbl. | | 1981 | 150 | 240 | w/4bbl |
† California Emissions
Years:1976-1980
Dualjet 2 bbl carb version with 8.5:1 compression.
267
The 267 was introduced in 1979 for GM F-Body(Camaro), G-bodies (Chevrolet Monte Carlo, El Camino, and Malibu Classic) and also used on GM B-body cars (Impala and Caprice models). The had the 350's crankshaft stroke of 3.48" and the smallest bore of any small-block, 3.500 in. The 3.500" bore was also used on the V6, which was introduced a year earlier. (The 200 was a Chevrolet V6 engine based on the small block with the #3 and #6 cylinders removed).
It was available with a Rochester Dualjet 210 - effectively a Rochester Quadrajet with no rear barrels. After 1980, electronic feedback carburetion was used on the 267.
While similar in displacement to the other 4.3-4.4 L V8 engines produced by General Motors (including the Oldsmobile 260 and Pontiac 265, the small bore 267 shared no parts with the other engines and was phased out after the 1982 model year due to inability to conform to emission standards. Chevrolet vehicles eventually used the as its base V8 engine.
Years: 1980-1987
The LG4 was the "low output" (compared to the L69). It produced - and -. The addition of a knock sensor for the engine management system in 1985 allowed an increase in compression and a more aggressive spark timing map in the ECM. As a result power increased for the 1985 models to from the rating in 1984.
Years: 1983-1986
The L69 was the last true H.O. engine. The High Output , featuring higher compression of 9.5:1 with heads of the to-be-discontinued LU5 Cross-Fire fuel injection engine, and utilizing camshaft and 4" catalytic converter of the L83 which was used on the Corvette of 1982 and 1984. Complete with a 2.75 inch exhaust system, topped by a recalibrated 4-barrel carburetor, dual snorkel air cleaner assembly, aluminum intake manifold, aluminum flywheel, electric cooling fan, and furthermore a knock sensor including more aggressive spark timing, this engine produced @ 4800 and of torque @ 3200 rpm. In most cases, being mated to a 3.73 or 3:42 ratio limited slip rear axle and a T5 5-speed or 700R4 automatic, this engine provided its driver with a wide range of rpm to play in.
Years: 1981-1986
The LE9 was the truck/van version of the High Output 305. It also had flattop pistons for a 9.5:1 compression ratio, the "929" truck 350 camshaft for more torque, 14022601 casting heads featuring 1.84/1.50" valves and 58 cc chambers, a specially calibrated 4bbl Q-Jet, the hybrid centrifugal/vacuum advance distributor with ESC knock sensor setup, and lower restriction exhaust. The engine made @ 4,600 and @ 2,000 rpm.
Years: 1985-1992
Introduced in 1985, the LB9 was the first Chevrolet small block to have tuned-port fuel injection (TPI). It was introduced with and and varied between - (with - of torque) over the years offered. It was an option on all 1985-1992 Chevrolet Camaro & Pontiac Firebird models.
Years: 1987-95
The L03 was the "low output" (compared to the 305 TPI LB9). It produced and of torque ( at 4,400 rpm and at 2,400 in 1993-1995 GM trucks). This engine used throttle-body fuel injection. The TBI uses a unique injector firing scheme: for every rotation of the engine, each injector fired twice.
Major changes
The original design of the small block remained remarkably unchanged for its production run, which began in 1955 and ended, in passenger vehicles, in 2003. The engine is still being built today for many aftermarket applications, both to replace worn-out older engines and also by many builders as high-performance applications. The principal changes to it over the years include:
- 1956 - Oil filtration was introduced, using a sock style filter in a canister.
- 1957 - The engine came with only front mounts, the side mount bosses were present but not drilled and tapped leaving its retrofitting problematic.
- 1962 - The block's cylinder wall casting was revised to allow four inch bores. Previously, only certain years of the 283 engine (1958-1962) could be bored safely to four inches.
- 1968 - The main journal diameter was increased to 2.45 in from 2.30 in and the connecting rod journal diameter was increased to 2.10 in from 2.00 in. This allowed the use of cast iron crankshafts as the previous parts were made of forged steel. The rod bolts were changed from 11/32 in. diameter to 3/8 inch. Additionally, the canister/sock style oil filter was now converted to use spin on filters. The oil fill location was moved from a tube on the front of the intake manifold to a cap on either side valve cover.
- 1986 - The rear main seal was changed from a 2-piece rubber design to a 1-piece rubber design that used a mounting appliance to hold it in place. This necessitated a change in the flywheel/flexplate bolt pattern as well.
- 1987 - The valve cover surfaces were changed such that cylinder head mounting lip was raised and the bolt location was moved from 4 bolts on the perimeter, to 4 bolts down the centerline of the valve cover (this design debuted on the Corvette in 1985, and Chevrolet 4.3 L the year before). Also changed were the mounting angles of the center 2 bolts on each side of the intake manifold (from 90 degrees to 73 degrees) and the lifter bosses were increased in height to accept roller lifters. The alloy heads for use in the Corvette still retain the non-angled bolts (center 2 bolts attaching to the intake). Also all carburetors were done away with and replaced by TBI (throttle-body injection) fuel injection that acts some what like a carburetor.
- 1996 - This was the last change for the Generation I engine, and continued through the end of the production run in 2003; all 1997-2003 Generation I engines were Vortec truck engines. The cylinder heads were redesigned using improved ports and combustion chambers similar to those in the Generation II LT1, resulting in significant power increases. The intake manifold bolt pattern was also changed from four bolts per cylinder head instead of the traditional six.and it was very crazy thing to have
See also
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