Chevrolet Small-Block engine

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Chevrolet Small-Block engine
Manufacturer:General Motors
Production:1955–2000
Successors:GM LT engine, GM LS engine
Type:small-block V8
265
Production:1954–1956
Displacement:265 in³ (4.3 L)
Power:162–240 hp (121–179 kW)
Applications:1954–1956 Chevrolet Corvette
1955 Chevrolet Sedan
283
Production:1957–1967
Displacement:283 in³ (4.6 L)
Power:220–315 hp (164–235 kW)
Applications:1957–1962 Chevrolet Corvette
1960–1967 Chevrolet Impala
307
Production:1968–1973
Displacement:307 in³ (5.0 L)
Power:115–200 hp (86–149 kW)
327
Production:1962–1968
Displacement:327 in³ (5.4 L)
Power:250–360 hp (186–268 kW)
Applications:1962–1968 Chevrolet Corvette
302
Production:1967–1969
Displacement:302 in³ (4.9 L)
Power:290 hp (216 kW)
Applications:1967–1969 Chevrolet Camaro Z28
400
Production:1970–1979
Displacement:400 in³ (6.6 L)
Power:240 hp (179 kW)
262
Production:1975–1976
Displacement:262 in³ (4.3 L)
Power:110 hp (82 kW)
Applications:1975–1976 Chevrolet Monza
305
Production:1976–1992
Displacement:305 in³ (5.0 L)
Power:130–250 hp (97–186 kW)
Applications:1976–1979 Chevrolet Monza
1976–1979 Chevrolet Camaro
350
Production:1969–2000
Displacement:350 in³ (5.7 L)
Power:125–370 hp (93–276 kW)
Applications:1969–1991 Chevrolet Corvette
1975 Chevrolet Monza

Contents

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Introduction

Chevrolet's small-block V8 is a famous automobile engine. Nicknamed "mouse motor" for its compact dimensions compared to other V8 engines of the time, production began in 1955 with the 265 in³ (4.3 L) engine used to bring performance credentials to the Corvette. The displacement changed over the years, eventually reaching 400 in³ (6.6 L), but none caught on like the 350 in³ (5.7 L) small-block. This engine is still in production today at General Motors Toluca Mexico plant, but is no longer offered in current model year vehicles since the year 2000. Its production numbers were impressive, with more than 90,000,000 built.

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

Although Buick, Cadillac, Oldsmobile, and Pontiac also designed V8 engines (see list of GM engines), it was Chevrolet's 350 in³ small-block that became the GM corporate standard. Over the years, every American General Motors division used the Chevrolet small-block, and its descendents (see GM LT engine and GM LS engine) continue as the company's mainstream V8 design today.

The small-block was on the Ward's 10 Best Engines of the 20th Century list.

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Major Versions

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Generation 1

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. There were, however many minor changes made to the engine over the years; these changes are listed below.

  • 1955 - The first year of introduction in 265 in³ only. As was fairly common for the time, no provision for an oil filter was included in the engine design.
  • 1956 - Oil filtration was introduced, using a sock style filter in a canister.
  • 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. In addition, 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 timing cover to a cap on either side valve cover.
  • 1986 - The troublesome leaky 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 1984, and Chevrolet 4.3L the year before). The troublesome rear main seal was changed from a 2-piece rope design to a 1-piece design that used a mounting appliance to hold it in place. This necessitated a change in the flywheel/flexplate bolt pattern as well. Also changed were the mounting angles of the center 2 bolts on each side of the intake manifold and the lifter bosses were increased in height to accept roller lifters.
  • 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. This change resulted in significant power increases.
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SB2

This engine was produced from 1996 to the present for racing applications only. The cylinder heads were redesigned and the lifter bores were offset. The valve sequence for each head was changed from the traditional E-I-I-E-E-I-I-E to a new I-E-I-E-E-I-E-I and because of this the camshaft was redesigned.

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Generation II

See the GM LT engine page for more information on the newer small-block V8s.

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Generation III / IV

See the GM LS engine page for more information on the newest small-block V8s.

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Early Small Blocks

Most current GM small-block V8s (the LT and LS series) trace their lineage to the 1955 265 in³ V8 developed for the Corvette. Displacement and power eventually reached 327 in³ and 509 hp (in prototypes) before the Corvette switched to Chevrolet big-block power. But the small-block lived on, settling in at 350 in³ for decades of performance.

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265

The 265 in³ (4.3 L) V8 was the first Chevrolet small block. Designed by Ed Cole's group at Chevrolet, it filled the power gap in the 1955 Corvette lineup, producing an impressive 195 hp (145 kW). The little engine went from drawings to production in just 15 weeks. Besides its compact dimensions, the small-block was known for its novel green-sand foundry construction process.

Dimensions were oversquare - 3.75 in (95 mm) bore and 3 in (76 mm) stroke. The small-block's 4.4 in (111.8 mm) bore spacing would continue in use for decades. It was a pushrod cast-iron engine with solid lifters and a 4-barrel Rochester carburetor. A passenger car version produced 162 hp. The first two production years of this motor had no provision for oil filtration, and as such the engine is undesirable to all but period collectors.

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

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283

The 283 in³ (4.6 L) V8 was introduced in 1957. It was a version of the 265 in³ (4.3 L) bored-out to 3.87 in (98 mm). There were five different versions ranging from 185 hp to 283 hp (164 kW to 211 kW) 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 engine featured Ramjet mechanical fuel injection, allowing the engine to produce 1 hp per cubic inch, an impressive feat at the time. For 1961, an amazing 315 hp was available from this unit.

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302

Chevrolet produced a special 302 in³ (4.9 L) engine for Trans Am racing. It was the product of placing the 3-inch stroke crankshaft from a 283 into a 4-inch bore 327 block. This engine was only used in the first-generation Camaro Z28. Conservatively rated at 290 hp (216 kW), actual output was at least 320 hp (239 kW). This block is one of 3 displacements that underwent a transformation for the 1968/1969 period when the main bearing size was increased from 2.30 in to 2.45 in.

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307

A 307 in³ (5.0 L) 307 version was produced from 1968 through 1973. Engine bore was 3.875 in (98.4 mm).

The 307 replaced the 283 in Chevrolet cars and produced 200 hp (149 kW) SAE gross 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 motor.

The 307 was also unique in the fact that its casting alloy had a very low nickel content making it relatively soft. Due to this fact, this engine has low value among rebuilders because of reduced longevity.

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327

The 327 in³ (5.4 L) V8, introduced in 1962, was bored and stroked to 4 in (102 mm) by 3.25 in. Power ranged from 250 hp to 375 hp (186 kW to 280 kW) depending on the choice of carburetor or fuel injection. The L76 version produced 340 hp (254 kW) and 344 ft·lbf (466 N·m), while the L84 was the top performer with 360 hp (268 kW) and 352 ft·lbf (477 N·m) with solid lifters, a special cam, and Ram-Jet fuel injection. The 1966 L79 was the highest-performance that year 327 at 350 hp (261 kW) and 360 ft·lbf (477 N·m). * 1963-1968 Chevrolet Corvette. This block is one of 3 displacements that underwent a major change in 1968/1969 when the main bearing size was increased from 2.30 in to 2.45 in.

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400

A 400 in³ small-block was introduced in 1970 and produced for 10 years. It had a 4.125 inch bore and a 3.75 inch stroke. Initial output was 240 hp. While popular with circle-track racers, the engine was prone to cooling troubles if cylinder heads from other blocks were fitted without proper modifications. The 400 produced a lot of torque at low RPMs compared to the other displacements and was used primarily in pickup trucks and the large B-cars (Caprice/Impala) but also found use in Vans which could not take a big-block motor. The 400 was eventually discontinued due to its inability to meet EPA emission regulations in place in the early 1980's.

The 400 was unique compared to all other displacements for 3 reasons:

  • Due to the siamesing of the cylinder bores in the casting - there was no space between adjacent cylinder liners - this block was rather rigid and not prone to the cylinder bore flexing of the other displacements.
  • This block used a much larger 2.65 inch main bearing assuring that crankshafts from all other blocks would not fit without special oversize bearings.
  • This is the only small-block that used a 5.56 inch long connecting rod compared to the 5.7 inch connecting rod in all other displacements.

While Chevrolet never produced a factory performance version of the 400, it is highly sought out among racers who participate in the very popular 406 racing class - so named for the displacement created by a minor overbore. Destroking a 400 block with a 350 crankshaft creates a 377, a popular combination for dirt track racers. 400 blocks are nearly impossible to find as salvage today and as such the racing market is fed by 3rd party manufacturers who offer improved versions of the block.

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Later Small Blocks

This section documents the odd-size small blocks developed after the 350 appeared in 1969. Many of these basic blocks are variations of the 350 design.

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262

The 262 was a 4.3 L (262 in³) 90° pushrod V8 with an iron block and heads. Bore and stroke were 3.67 in (93 mm) by 3.10 in (78.7 mm). Power output for 1975 was 110 hp (82 kW) and 195 ft·lbf (264 N·m). Although underpowered, the 262 was replaced by the 305 the following year.

This engine was used in the following cars:

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267

Introduced in 1979 for GM A-bodies (Chevrolet Monte Carlo, El Camino, and Malibu Classic) and also used on GM B-body cars (Impalas and Caprices), the 267 is actually a debored 305. The 350's crankshaft stroke (3.48") was the same, and to date, the only small-block with the smallest bore - 3.500 in.

It was available with a Rochester Dualjet 210 - effectively, one half of a Rochester Quadrajet. After 1980, electronic feedback carburetion was used on the 267.

While similar in displacement to the other 4.3-4.4L V8 motors produced by General Motors (including the Oldsmobile 260 and Pontiac 265, the small bore 267 shared no parts with the other motors and was phased out after the 1982 model year due to inability to conform to emission standards. Chevrolet vehicles eventually used the 305 (their own 5.0L) coupled with a THM200-4R overdrive.

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305

The 305 variant of the small-block Chevrolet was bored and stroked to 5.0 L (305 in³) with a 3.74 in (95 mm) bore and 3.48 in (88.4 mm) stroke - taken from the 350.

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

After 1994, its usage was limited to light trucks and SUVs as the Vortec 5000.

Year hp (kW)  ft·lbf (N·m)
1976 140 250 w/2bbl.
1977 145 245 w/2bbl.
1978 140 240 w/2bbl.
1978 160 235 w/4bbl.
1979 125 235 w/2bbl.
1979 130 245 w/2bbl.
1979 155 225 w/4bbl.
1979 160 235 w/4bbl.
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LG4

Years: 1982-1987

The LG4 was the "low output" 305 in³/ 5.0L (compared to the L69). It produced 165–190 hp (110–125 kW) and 240–250 ft·lbf (325–340 N·m). The addition of a knock sensor for the engine management system in 1985 allowed an increase in compression and a more aggressive spark timing map in the ECM. As a result power increased for the 1985 model year by over 20 hp.

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LO3

Years: 1987-93

The LO3 was the "low output" 305 in³/ 5.0L (compared to the TPI 305). It produced around 175 hp and 260 ft·lbf of torque. The 305 dropped the Computer-controlled carbureter and received the fuel-injected TBI (throttle-body injection). The TBI unit consisted of two barrels, much like those of a two barrel carb, but instead of "jets", there was a fuel-injector placed above each barrel, resulting in a 2-barrel, 2-injector setup. The LO3 used a "batch fire" setup. For every rotation of the engine, each injector fired twice.

TBI injection was still used on trucks through 1995, mainly because of it's strong torque curve, allowing for heavy towing and hauling. Some trucks even received a 454 in³/ 7.4L TBI engine.

The 305 was used in the following cars:

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350

The first generation of Chevrolet small-blocks began with the 1955 Chevrolet 265 in³ (4.3 L) V8. But it was the 350 in³ (5.7L) series that set the standard for high performance. The engine's physical dimensions (oversquare 4.00 in bore and 3.48 in stroke, 102 mm by 88 mm) are nearly identical to the 400 hp (300 kW) LS2 engine of today, but of course much has changed. It is by far the most widely used Chevrolet small-block; from the factory, it was installed in everything from station wagons to sports cars to heavy trucks.

Note that Oldsmobile produced an entirely different 350 in³ V8 (4.057 in bore and 3.53 in stroke, 103 mm by 90 mm), the L34 and LF9 from the 1980s.

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ZQ3

Years: 1969, 1970, 1972-1975

The ZQ3 was the standard engine in the 1969-1970 Chevrolet Corvette. It was a 300 hp (224 kW) version of the 350 in³ (5.7 L) small-block, with 10.25:1 compression and hydraulic lifters. It used a Rochester "4MV" Quadra-Jet 4-barrel carburetor. This was the first block produced that featured the larger 2.45 inch main bearing versus the older 2.30 inch main bearing in 1968/1969.

The 1972 ZQ3 produced 200 hp (150 kW) and 300 ft·lbf (407 N·m) with 8.5:1 compression, dropping another 10 hp (7.5 kW) in 1973. 1975 saw the ZQ3 at 165 hp (123 kW) and 255 ft·lbf (346 N·m).

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L46

Years: 1969, 1970, 1972

The L46 was an optional engine on the 1969-1970 Chevrolet Corvette. It was a 350 hp (261 kW), 380 ft·lbf (515 N·m) version of the ZQ3 with higher 11:1 compression. The 1972 ZQ3 produced just 200 hp (150 kW) and 300 ft·lbf (407 N·m) with an 8.5:1 compression ratio.

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LT-1

Years: 1970-1972

The LT-1 was the ultimate 350 V8, becoming available in 1970. It used solid lifters, 11:1 compression, a high-performance camshaft, and a Holley four-barrel carburetor on a special aluminum intake to produce 370 hp (276 kW) and 380 ft·lbf (515 N·m). It was available on the Corvette and Camaro Z28. Power was down in 1971 to 330 hp (246 kW) and 360 ft·lbf (477 N·m) with 9:1 compression, and again in 1972 (the last year of the LT-1) to 255 hp (190 kW) and 280 ft·lbf (380 N·m).

Note that there was a later small-block engine called the "LT1".

More information

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L48

Years: 1971-1980

The L48 was the standard engine on the 1971 Chevrolet Corvette. It produced 270 hp (201 kW) and 360 ft·lbf (477 N·m) with an 8.5:1 compression ratio.

The 1976-1979 L48 was the standard Corvette engine and produced 180 hp (134 kW) and 270 ft·lbf (366 N·m). The 1980 L48 stood at 190 hp (142 kW) and 280 ft·lbf (380 N·m) from 8.2:1 compression.

In 1973 the "L-48" had cold air induction (throttle activated) and developed 190 hp (net). Beginning in 1974 the hp was reduced for several years until it reached a low of 165 (net) in 1975 or '76, before rising again.

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L82

Years: 1973-1980

The 1973-1974 L82 was a performance version of the 350 producing 250 hp (186 kW) and 285 ft·lbf (386 N·m) from 9:1 compression. It was down to 205 hp (153 kW) and 255 ft·lbf (346 N·m) for 1975. It was the optional engine again in 1976-1977, producing 5 hp (4 kW) more. The 1978 L82 recovered somewhat, producing 220 hp (164 kW) and 260 ft·lbf (353 N·m), and 5 hp (4 kW) and 10 ft·lbf (14 N·m) more for 1979. 1980 saw another 10 hp (7.5 kW) and 15 ft·lbf (20 N·m).

More information

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L81

Years: 1981

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

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L83

Years: 1982, 1984

The 1982 L83 was again the only Corvette engine (and only available with an automatic transmission) producing 200 hp (150 kW) and 285 ft·lbf (386 N·m) from 9:1 compression. This was again the only engine on the new 1984 Vette, at 205 hp (153 kW) and 290 ft·lbf (393 N·m). The L83 added Cross-Fire fuel injection (twin throttle-body fuel injection).

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L98

Years: 1985-1992

The new 1985 L98 added tuned-port fuel injection, which was good for 230 hp (172 kW) and 330 ft·lbf (447 N·m). It was standard on all 1985-1991 Corvettes. 1987 versions had 10 hp (7.5 kW) and 15 ft·lbf (20 N·m) more thanks to 9.5:1 compression. Compression was up again in 1991 to 10:1 but output stayed the same.

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LM1

The LM1 is the base 350 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.

More information

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See also

From the 1950s through the 1970s, each GM division had its own V8 engine family. Many were shared among other divisions, but each design is most-closely associated with its own division:

GM later standardized on the later generations of the Chevrolet design:

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References

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