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Chevrolet Big-Block engine

Chevrolet Big-Block engine

The Chevrolet "Big Block" is a term for a series of large displacement V8 engines that have been developed and produced in the United States from the 1950s until 2009. As American automobiles grew in size and weight following the Second World War, the engines powering them had to keep pace. Chevrolet had introduced its popular small block V8 in 1955, but needed something larger to power its medium duty trucks and the heavier cars that were on the drawing board.

Chevrolet big-block engine
ManufacturerGeneral Motors
ConfigurationNaturally aspirated 90° V8
Displacement348 cu in (5.7 L)
366 cu in (6.0 L)
396 cu in (6.5 L)
402 cu in (6.6 L)
409 cu in (6.7 L)
427 cu in (7.0 L)
454 cu in (7.4 L)
496 cu in (8.1 L)
502 cu in (8.2 L)
572 cu in (9.4 L)
632 cu in (10.4 L)
Cylinder bore3.935 in (99.9 mm)
4.09 in (103.9 mm)
418 in (104.8 mm)
414 in (108.0 mm)
4.31 in (109.5 mm)
4.466 in (113.4 mm)
4.56 in (115.8 mm)
Piston stroke314 in (82.6 mm)
312 in (88.9 mm)
3.65 in (92.7 mm)
3.76 in (95.5 mm)
4 in (101.6 mm)
4.37 in (111.0 mm)
438 in (111.1 mm)
Block materialCast iron
Head materialCast iron, Aluminum
ValvetrainOHV 2 valves x cyl.
Compression ratio8.5:1, 9.0:1, 10.25:1, 11.0:1, 12.0:1, 12.5:1, 13.5:1
Fuel systemCarburetor
Fuel injection (Since Gen. V)
Fuel typeGasoline
Cooling systemWater-cooled
Power output250–720 hp (186–537 kW)
Torque output385–690 lb⋅ft (522–936 N⋅m)
Dry weight665–685 lb (302–311 kg)

W-series (Mark I)

The first version of the "Big Block" V8 Chevrolet engine, known as the W-series, was introduced in 1958. Chevrolet designed this engine for use in passenger cars and light trucks. This engine had an overhead valve design with offset valves and uniquely scalloped rocker covers, giving it a distinctive appearance. The W-series was produced from 1958 to 1965, and had three displacement options:

  • 348 cu in (5.7 L), available from 1958 to 1961 in cars, and in light trucks through 1964;

  • 409 cu in (6.7 L), available from 1961 to 1965; and

  • 427 cu in (7.0 L), available in 1962 and 1963.

The W-series engine was made of cast iron. The engine block had 4.84-inch (123 mm) bore centers, two-bolt main bearing caps, a "side oiling" lubrication system (the main oil gallery located low on the driver's side of the crankcase), with full-flow oil filter, and interchangeable cylinder heads. Heads used on the high performance 409 and 427 engines had larger ports and valves than those used on the 348 and the base 409 passenger car and truck engines, but externally were identical to the standard units. One minor difference between the 348 and 409/427 was the location of the engine oil dipstick: it was on the driver's side on the former and the passenger's side on the latter. No satisfactory explanation was ever offered for why this change was made. However, it did provide a fairly reliable way to differentiate between the smaller and larger versions of the engine.

As with the 265 and 283 cu in (4.3 and 4.6 L) "Small Block" engines, the W-series valve gear consisted of tubular steel pushrods operating stud-mounted, stamped-steel rocker arms. The push rods also acted as conduits for oil flow to the valve gear. Due to the relatively low mass of the valve train, mechanical lifter versions of the W-series engine were capable of operating at speeds well beyond 6000 RPM.

The combustion chamber of the W-series engine was in the upper part of the cylinder, not the head, the head having only tiny recesses for the valves. This arrangement was achieved by combining a cylinder head deck that was not perpendicular to the bore with a crowned piston, which was a novel concept in American production engines of the day. As the piston approached top dead center, the angle of the crown combined with that of the head deck to form a wedge-shaped combustion chamber with a pronounced quench area. The spark plugs were inserted vertically into the quench area, which helped to produce a rapidly moving flame front for more complete combustion.

The theory behind this sort of arrangement is that maximum brake mean effective pressure (BMEP) is developed at relatively low engine speeds, resulting in an engine with a broad torque curve. With its relatively flat torque characteristics, the "W" engine was well-suited to propelling both the trucks and heavier cars that were in vogue in the USA at the time. The W-series was a physically massive engine when compared to the "Small Block" Chevrolet engine. It had a dry weight of approximately 665 pounds (302 kg), depending on the type of intake manifold and carburetion systems present.


The first iteration of the W-series engine was the 1958 "Turbo-Thrust" 348-cubic-inch (5.7 L), originally intended for use in Chevrolet trucks but also introduced in the larger, heavier 1958 passenger car line. Bore and stroke was 4 1⁄8 in × 3 1⁄4 in (104.8 mm × 82.6 mm), resulting in a substantially oversquare design. This engine was superseded by the 409 cu in (6.7 L) as Chevrolet's top performing engine in 1961 and went out of production for cars at the end of that year. It was produced through 1964 for use in large Chevrolet trucks.

With a four-barrel carburetor, the base Turbo-Thrust produced 250 hp (186 kW). A special "Tri power" triple-two-barrel version, called the "Super Turbo-Thrust", produced 280 hp (209 kW). A "Special Turbo-Thrust" further upped the power output to 305 hp (227 kW) with a single large four-barrel carburetor. Mechanical lifters and triple two-barrel carburetors brought the "Special Super Turbo-Thrust" up to 315 hp (235 kW). For 1959 and 1960, high-output versions of the top two engines were produced with 320 hp (239 kW) and 335 hp (250 kW) respectively. In 1961, power was again increased to 340 hp (254 kW) for the single four-barrel model, and 350 hp (261 kW) when equipped with triple two-barrels.

First YearLast YearModel NameFeaturesPower (Advertised Gross)
19581961Turbo-Thrust4 barrel250 hp (186 kW)
Super Turbo-Thrust"Tri-Power" 3x2 barrel280 hp (209 kW)
Special Turbo-Thrust4 barrel305 hp (227 kW)
1960Special Super Turbo-Thrust"Tri-Power" 3x2 barrel315 hp (235 kW)
1959Special Turbo-Thrust4 barrel320 hp (239 kW)
1961Special Super Turbo-Thrust"Tri-Power" 3x2 barrel335 hp (250 kW)
1960Special Turbo-Thrust4 barrel340 hp (254 kW)
Special Super Turbo-Thrust"Tri-Power" 3x2 barrel350 hp (261 kW)


A 409 cu in (6.7 L) version was Chevrolet's top regular production engine from 1961 to 1965, with a choice of single or 2X4-barrel Rochester carburetors. Bore x stroke were both up from the 348 cu in (5.7 L) to 4.31 in × 3 1⁄2 in (109.5 mm × 88.9 mm). On December 17, 1960, the 409 engine was announced along with the Impala SS (Super Sport) model. The initial version of the engine produced 360 hp (268 kW) with a single 4-barrel Carter AFB carburetor. The same engine was upped to 380 hp (283 kW) in 1962. A 409 hp (305 kW) version of this engine was also available, developing 1 hp per cubic inch with a dual four-barrel aluminum intake manifold and two Carter AFB carburetors. It had a forged steel crankshaft.[4] This dual-quad version was immortalized in the Beach Boys song titled "409".

In the 1963 model year, output reached 425 bhp (431 PS; 317 kW) @ 6000 rpm and 425 lb⋅ft (576 N⋅m) @ 4200 rpm of torque with the Rochester 2X4-barrel carburetor setup, a compression ratio of 11:1 and a solid lifter camshaft.[5] The engine was available through mid-1965, when it was replaced by the 396 cu in (6.5 L) 375 hp (280 kW) Mark IV big-block engine. In addition, a 340 hp (254 kW) version of the 409 engine was available from 1963–1965, with a single 4-barrel cast iron intake mounting a Rochester 4GC square-bore carburetor, and a hydraulic-lifter camshaft.

427 (Z11)

A special 427-cubic-inch (7.0 L) version of the 409 engine was used in the 1963 Impala Sport Coupé, ordered under Chevrolet Regular Production Option (RPO) Z11.[6] This was a special package created for drag racers, as well as NASCAR,[7] and it consisted of a 427 cu in (7.0 L) engine with aluminum body parts, and a cowl-induction air intake system. The aluminum body parts were fabricated in Flint, Michigan at the facility now known as GM Flint Metal Center.[8] Unlike the later, second-generation 427, it was based on the W-series 409 engine, but with a longer 3.65 in (92.7 mm) stroke. A high-rise, two-piece aluminum intake manifold and dual Carter AFB carburetors fed a 13.5:1 compression ratio to produce an under-rated 430 hp (321 kW) and 575 lb⋅ft (780 N⋅m). 50 RPO Z11 cars were produced at the Flint GM plant.

Extant GM Documents show 50 Z11 engines were built at the GM Tonawanda Engine plant for auto production, and 20 partial engines were made for replacement/over-the-counter use. Unfortunately, there is no evidence from GM that shows 57 cars were built.

Mark II

The so-called Mystery Motor, known internally as the Mark II or Mark IIS, is a race-only[9] engine produced for the 1963 season. Development began with a 409 cu in (6.7 L) version (Mark II) and ended with a 396 cu in (6.5 L) variant; however only the 427 cu in (7.0 L) engine (Mark IIS) was ever raced. It gained its nickname due to the incredible speeds cars equipped with it attained during its debut being considerably faster than the well known W-series powered cars. The engine was first used in Mickey Thompson's Z-06 Corvettes at Daytona in the 1963 Daytona 250 Miles - American Challenge Cup,[10] then in Smokey Yunick's Chevrolet 1963 Daytona 500 record-setting stock cars. This "secret" engine was a unique design incorporating aspects of both the W-series and the mid-1965 introduced Mark IV [9] referred to in sales literature as the "Turbo-Jet V8".

Mark III

Packard V-8 tooling and production rights were considered for purchase by Chevrolet. Project did not proceed.[11]

Mark IV

The Mark IV differed from the W-series engine in the placement of the valves and the shape of the combustion chambers. Gone was the chamber-in-block design of the W-series engine (which caused the power curve to drastically dip above 6500 rpm), and in its place was a more conventional wedge chamber in the cylinder head, which was now attached to a conventional 90 degree deck. The valves continued to use the displaced arrangement of the W-series engine, but were also inclined so that they would open away from the combustion chamber and cylinder walls, a design feature made possible by Chevrolet's stud mounted rocker arms. This alteration in valve placement resulted in a significant improvement in volumetric efficiency at high RPM and a substantial increase in power output at racing speeds. Owing to the appearance of the compound angularity of the valves[12], the automotive press dubbed the engine the "porcupine" design.

As part of the head redesign, the spark plugs were relocated so that they entered the combustion chamber at an angle relative to the cylinder centerline, rather than the straight-in relationship of the W-series engine. This too helped high RPM performance. Due to the new spark plug angle, the clearance provided by the distinctive scalloped valve covers of the W-series was no longer needed, and wide, rectangular covers were used.

In all forms (except the ZL-1 Can-Am model), the "rat motor", as it was later nicknamed (small-block engine being a "mouse motor"), was slightly heavier than the W-series model, with a dry weight of about 685 lb (311 kg). Aside from the new cylinder head design and the reversion to a conventional 90 degree cylinder head deck angle, the Mark IV shared many dimensional and mechanical design features with the W-series engine. The cylinder block, although more substantial in all respects, used the same cylinder bore pitch (bore spacing) of 4.84 in (123 mm) with a larger 2.75 in (70 mm) main bearing dimension, increased from the 2.5 in (63.5 mm) of the older engine (in fact, the shorter-stroke 348 and 409 crankshafts could be installed with the use of "spacer bearings" without modifying the crankshaft). Like its predecessor, the Mark IV used crowned pistons, which were castings for conventional models and impact extruded (forged), solid skirt types in high performance applications.

Also retained from the W-series design were the race-proven Moraine M400 aluminum bearings first used in the 409, as well as the highly efficient "side oiling" lubrication system, which assured maximum oil flow to the main and connecting rod bearings at all times. Later blocks intended for performance use had the main oil gallery moved up to the cam bearing bore area and provided "priority main" oiling, improving the oil system even further.


The 366 cu in (6.0 L) Big Block V-8 gasoline engine was used only in Chevrolet medium duty trucks and in school buses. It had a bore and a stroke of 3.935 in × 3.76 in (99.9 mm × 95.5 mm). This engine was made from the 1960s until the mid-1990s. The 366 used 4 rings on the pistons, as it was designed from the very beginning as a truck engine. The 366 was produced only as a tall-deck engine, with a deck 0.4 in (10 mm) taller than the 396, 402, and 454 short-deck Big Blocks.

396 and 402

The 396 cu in (6.5 L) V8 was introduced in the 1965 Corvette as the L78 option and in the Z16 Chevelle as the L37 option. It had a bore x stroke of 4.094 in × 3.760 in (104 mm × 95.5 mm),[13][14] and produced 375 bhp (380 PS; 280 kW) at 5600 rpm and 415 lb⋅ft (563 N⋅m) of torque at 3600 rpm.[15] The solid lifter version was capable of being operated in the upper 6000 rpm range, and when installed in the 1965 Corvette, was factory-rated at 425 hp (317 kW).

Introduced in 1970, the 402 cu in (6.6 L) was a 396 cu in (6.5 L) bored out by 0.03 in (0.76 mm). Despite the fact that it was 6 cubic inches (98 cc) larger, Chevrolet continued marketing it under the popular "396" label in the smaller cars while at the same time labeling it "Turbo-Jet 400" in the full-size cars.

Power rating(s) by year:

  • 1965: 375 hp (280 kW)/425 hp (317 kW)

  • 1966: 325 hp (242 kW)/350 hp (261 kW)/360 hp (268 kW)/375 hp (280 kW)

  • 1967: 325 hp (242 kW)/350 hp (261 kW)/375 hp (280 kW)

  • 1968: 325 hp (242 kW)/350 hp (261 kW)/375 hp (280 kW)

  • 1969: 265 hp (198 kW)(2bbl)/325 hp (242 kW)/350 hp (261 kW)/375 hp (280 kW)

  • 1970: 330 hp (246 kW)/350 hp (261 kW)/375 hp (280 kW)

  • 1971: 300 hp (224 kW) SAE gross; while SAE net was 260 hp (194 kW) for dual exhaust and 206 hp (154 kW) for single exhaust

  • 1972: 240 hp (179 kW) SAE net for dual exhaust and 210 hp (157 kW) SAE net for single exhaust

Used in:

  • 1965 Chevrolet Corvette

  • 1965–1972 Chevrolet Chevelle

  • 1967–1972 Chevrolet Camaro

  • 1968–1970 Chevrolet Nova

  • 1970–1972 Chevrolet Monte Carlo, Chevrolet trucks

  • 1965–1972 Chevrolet Biscayne, Chevrolet Bel Air, Chevrolet Impala, Chevrolet Impala SS, Chevrolet Caprice

396 and 402 Production codes

  • L-34: produced 1966-9, 10.25:1 compression, Holley (Q-jet 1968-9) carburetor, hydraulic lifters, oval port closed chamber heads, forged steel crankshaft, and two-bolt main caps. It produced 350 to 360 hp (261 to 268 kW).[16]

  • L-35: produced 1965-9, had 10.25:1 compression, Q-jet carburetor, forged steel (1965-7) or nodular iron (1968-9) crankshaft, hydraulic lifters, oval port closed chamber heads, and two-bolt main caps. It produced 325 hp (242 kW).[16]

  • L-37: similar to L-78 except for having hydraulic lifters and slightly milder cam; 2-bolt main caps; designed specifically for the 1965 Z16 Chevelle

  • L-66: produced 1969, rare two-barrel carburetor, 9:1 compression, nodular iron crankshaft, hydraulic lifters, oval port closed chamber heads, and two-bolt main caps. It produced 265 hp (198 kW).[16]

  • L-78: produced 1965-9, had a Holley 800 cu ft/min (23 m3/min) carburetor, compression ratio 11:1, forged pop-top pistons, aluminum high-rise intake manifold, steel crankshaft, solid lifter cam (same as the L-72), rectangular ("square") port closed chamber heads, and four-bolt main caps. It produced 375 bhp (280 kW) in mid-size cars, 425 bhp (317 kW) in Corvettes.[16]

  • LS-3: produced 1970-2, 10.25:1 (1970) or 8.5:1 (1971) compression, hydraulic lifters, nodular iron crankshaft, and two-bolt main caps. It produced 330 hp (246 kW) (1970), 300 hp (224 kW) (1971), 210 or 240 hp (157 or 179 kW) (1972 net horsepower, single or dual exhaust).[16]

  • L-34: produced 1970. Same as 396 cu in (6.5 L) L-34.

  • L-78: produced 1970. Same as 396 cu in (6.5 L).


L36 427 in a 1966 Chevrolet Corvette
L71 427 in a 1967 Chevrolet Corvette

The highly successful and versatile 427 cu in (7.0 L) version of the Mark IV engine was introduced in 1966 as a production engine option for full-sized Chevrolets and Corvettes. The bore was increased to 4 1⁄4 in (108 mm), with power ratings varying widely depending on the application. There were smooth running versions with hydraulic lifters suitable for powering the family station wagon, as well as rough-idling, high-revving solid lifter models usually applied to a minimally equipped, plain-looking, two-door Biscayne sedan fitted with the 425 hp (317 kW) version of the 427 - (RPO L72).

Perhaps the ultimate 427 for street applications was the 435 bhp (441 PS; 324 kW) at 5800 rpm and 460 lb⋅ft (624 N⋅m) at 4000 rpm of torque L71 version available in 1967 to 1969 Corvettes, and in the Italian Iso Grifo. This engine was identical to the 425 hp (317 kW) L72 427 (first introduced in 1966), but was fitted with 3X2-barrel Holley carburetors,[17] known as "Tri-Power", in lieu of the L72's single 4-barrel carburetor. Both engines used the same high-lift, long-duration, high-overlap camshaft and large-port, cast-iron heads to maximize cylinder head airflow (and, hence, engine power) at elevated engine-operating speeds. Consequently, the engines offered very similar performance and resulted in a car whose performance was described by one automotive journalist as "the ultimate in sheer neck-snapping overkill". Typical magazine road tests of the day yielded 0-60 mph (97 km/h) in 5.6 seconds and 1⁄4 mile (402 m) in 13.8 second at 104 mph (167 km/h) range for both the L72 and L71.[18][19]

In 2011, Super Chevy Magazine conducted a chassis dynamometer test of a well documented, production-line, stock but well-tuned L-72 "COPO" Camaro, and recorded a peak 287 hp (214 kW) at the rear wheels, demonstrating the substantial difference between 1960s-era SAE "gross" horsepower ratings and horsepower at the wheels on a chassis dynomometer. Wheel horsepower (which is obtained at the drive wheels and thus takes into account drivetrain power loss) does not equate to SAE net HP (which is horsepower at the flywheel, like SAE gross, but with all accessories included, unlike SAE gross). [20]

The RPO L89 was an L71 fitted with aluminum heads. While this option produced no power advantage, it did reduce engine (and hence, vehicle) weight by roughly 75 pounds (34 kg). This resulted in superior vehicle weight distribution for improved handling, although the difference in straight line performance was negligible.

The 1969 ZL1 version of the 427 engine was developed primarily for Can-Am racing, where it was very successful in cars like the McLaren M8B. The ZL1 specifications were nearly identical to the production L88 version of the 427, but featured an all-aluminum cylinder block, in addition to aluminum cylinder heads, which dropped the total engine weight into small-block territory (approx. 575 lb or 261 kg dressed). The first Corvette RPO ZL1 engine package was built in late Fall 1968 and featured aluminum closed chamber heads, until sometime in 1969, when the Corvette ZL1 engine changed to having open combustion chamber aluminum cylinder heads, as the 1969 L88 had. The ZL1 engine also featured a light weight aluminum water pump, a camshaft that was slightly "hotter" than the L88's, and a specially tuned aluminum intake manifold. Like the L88, the ZL1 required 103 octane (RON) (minimum) fuel, used an unshrouded radiator, and had poor low speed idle qualities - all of which made the two engines largely unsuitable for street use. (102 octane RON [Sunoco 260] represented the highest octane gasoline sold at common retail stations.)

As impressive as the ZL1 was in its day, actual engine dyno tests of a certified production line stock ZL1 revealed 376 hp (280 kW) SAE net with output swelling to 524 hp (391 kW) SAE gross with the help of optimal carb and ignition tuning, open long tube racing headers, and with no power-sapping engine accessories or air cleaner in place.[21] A second engine dyno test conducted on a second production line stock (but recently rebuilt and partially blueprinted) ZL1 revealed nearly identical figures for the various "gross" conditions.[22]

Period magazine tests of the ZL1 were quite rare due to the rarity of the engine itself. High-Performance Cars tested a production line stock, but well tuned, example and recorded a 13.1 second/110 mph (180 km/h) 1⁄4 mile (402 m), which correlates quite well with the previously referenced 376 hp (280 kW) SAE Net figure. Super Stock and Drag Racing Magazine recorded an 11.62 second/122.15 mph (196.58 km/h) 1⁄4 mile (402 m) in a ZL1 Camaro that was professionally tuned and driven by drag racing legend Dick Harrell, although that car was also equipped with open long-tube S&S equal-length headers, drag slicks, and minor suspension modifications. Using Patrick Hale's Power/Speed formula, the 122.15 mph (196.58 km/h) trap speed indicated low 11-second ET (elapsed time) potential (e.g. with larger drag slicks) and suggested something on the order of 495 hp (369 kW), "as installed", in that modified configuration. This large difference in power suggests that the OEM exhaust manifolds and exhaust system were highly restrictive in the ZL1 application, as was also the case with the similar L88.

The $4,718 cost of the ZL1 option doubled the price of the 1969 Corvette, but resulted in a car with exceptional performance for its day. Just two production Corvettes (factory option at dealer) and 69 Camaros (non-dealer option from factory - COPO 9560) were built with the ZL1.

Chevrolet capitalized on the versatility of the 427 design by producing a wide variety of high-performance, "over-the-counter" engine components as well as ready-to-race "replacement" engines in shipping crates. Some of the components were developed to enhance the engine's reliability during high RPM operation, possibly justifying the use of the description "heavy duty." However, most of these items were racing parts originally designed for Can-Am competition that found their way onto dealers' shelves, and were meant to boost the engine's power output.

Beginning in 1969, the highest performance 427 models were fitted with the new open (vs. closed) chamber cylinder heads, along with design improvements in crankshafts, connecting rods, and pistons, adopted from the Can-Am development program.

Chevrolet gave all 427 engines except the ZL1 a torque rating of 460 lb⋅ft (624 N⋅m).

Gross Power
19661969L364-barrel10.25:1390 hp (291 kW)
19661969L724-barrel + solid-lifters, more aggressive cam and high flow cylinder heads11.00:1425 hp (317 kW)[1]
19671969L68L36 with 3×2-barrel carbs.10.25:1400 hp (298 kW)
19671969L71L72 with 3×2 barrel carbs.11.00:1435 hp (324 kW)
19671969L89L71 + aluminum heads; RPO L89 also applied to L78 "375 HP" 396 engine with aluminum head option.11.00:1435 hp (324 kW)
19671969L88Racing-spec cam, high-flow aluminum heads (casting #s varied by model year) and some upgraded, competition-grade parts12.50:1[2]430 hp (321 kW)[3]
19691969ZL1Aluminum block with open chamber "3946074" aluminum heads (the early Corvette RPO engine featured a closed chamber head); cam even "hotter" than L88's; upgraded parts similar to L88's12.00:1430 hp (321 kW)
19701977(?)ZLXL88-ZL1 hybrid; iron block with aluminum heads12.25:1430 hp (321 kW)(?)


  • 1966–1969 Chevrolet Biscayne

  • 1966–1969 Chevrolet Caprice

  • 1966–1969 Chevrolet Impala

  • 1966–1969 Chevrolet Corvette

  • 1968–1969 Chevrolet Camaro (most were dealer installed, but in 1969 both the L-72 and the ZL-1 were factory options)

427 Production codes

  • LS-1: produced 1969, 10.25:1 compression, Q-jet carburetor, oval port closed chamber heads, hydraulic lifters, nodular iron crankshaft, and two-bolt main caps. It produced 335 hp (250 kW).[23]

  • L-36: produced 1966-9, had 10.25:1 compression, Holley or Q-jet carburetor, nodular iron crankshaft, hydraulic lifters, oval port closed chamber heads, and two-bolt main caps. It produced 385 hp (287 kW) in 1967–68 full-size cars, 390 hp (291 kW) in 1969 full-size cars and Corvettes (by exhaust system).[23]

  • L-68: produced 1967-9, had 10.25:1 compression, Tri-Power, nodular iron crankshaft, hydraulic lifters, aluminum oval port closed chamber heads, and two-bolt main caps. It produced 400 hp (298 kW), and was used in Corvettes.[23]


For 1970, the Big-Block was expanded again, to 454 cu in (7.4 L), with a bore x stroke of 4 1⁄4 in × 4 in (108.0 mm × 101.6 mm). The 1970 Chevrolet Corvette LS5 version of this engine was factory-rated at 390 bhp (395 PS; 291 kW) and 500 lb⋅ft (678 N⋅m), and the LS6 engine equipped with a single 4-barrel 800 cu ft/min (23 m3/min) Holley carburetor was upgraded to 450 bhp (456 PS; 336 kW) at 5600 rpm and 500 lb⋅ft (678 N⋅m) at 3600 rpm of torque.[24][25]

It has been suggested that the LS6 was nominally substantially underrated, which was a common practice of American car makers; and that the engine actually produced well over 500 hp (373 kW) as delivered from the factory. Indeed, the AHRA ASA (Showroom Stock Automatic) Class record-holding Chevelle LS-6 for the 1970 racing season posted a best-of-season trap speed of 106.76 mph (172 km/h),[26] which suggests something on the order of 350 "as installed" (SAE Net) HP for a 3,900 pounds (1,769 kg) car-and-driver combination. Indeed, Super Chevy Magazine conducted a chassis dyno test of a well-documented, well tuned, but stock 1970 LS-6 Chevelle and recorded 283 peak HP at the wheels[20] – a figure that lines up quite well with the previously referenced 350 SAE Net HP figure.

An even more powerful version, producing 465 hp (347 kW) and 610 lb⋅ft (827 N⋅m), of the 454, then dubbed LS-7 (not to be confused with the modern, mid 2000s, 7-litre Chevrolet Corvette engine that powered the C6 Z06), was also developed. Several LS-7 intake manifolds were individually produced and sold to the general public by a few Chevrolet dealers as optional performance parts. The LS-7 was later offered as a crate engine from Chevrolet Performance with an officially rated power minimum of 500 hp (373 kW) Gross.

In 1971, the LS-5 produced 365 hp (272 kW) and 550 lb⋅ft (746 N⋅m), and the LS-6 option came in at 425 hp (317 kW) and 575 lb⋅ft (780 N⋅m). In 1972, only the LS-5 remained, when SAE net power ratings and the move towards emission compliance resulted in a temporary output decline, due to lowered compression, to about 270 hp (201 kW) and 468 lb⋅ft (635 N⋅m). The 1973 LS-4 produced 275 hp (205 kW) and 468 lb⋅ft (635 N⋅m), with 5 hp (4 kW) and 10 lb⋅ft (14 N⋅m) gone the following year. Hardened valve seats further increased reliability and helped allow these engines to last much longer than the earlier versions, even without the protection previously provided by leaded fuel. 1974 was the last year of the 454 in the Corvette, although the Chevelle offered it in the first half of the 1975 model year. It was also available in the full size Impala/Caprice through model year 1976.

  • 1970–1976 Chevrolet Caprice

  • 1970–1975 Chevrolet Chevelle

  • 1970–1975 Chevrolet Monte Carlo

  • 1970–1975 Chevrolet El Camino

  • 1971–1972 GMC Sprint

  • 1970–1974 Chevrolet Corvette


General Motors introduced EFI in 1987, which was found on GM 2500 and 3500 trucks. The 454 EFI version was rated from 230 hp (172 kW) to 255 hp (190 kW) and from 385 lb⋅ft (522 N⋅m) to 405 lb⋅ft (549 N⋅m) of torque.

  • 1987-1990 Chevrolet C/K

  • 1987 GMC Suncrest

Commercial applications

Mark IV engines saw extensive application in Chevrolet and GMC medium duty trucks, as well as in Blue Bird Corporation's All American and TC/2000 transit buses (the latter up until 1995, using a 427 with purpose-built carburetor). In addition to the 427, a 366 cu in (6.0 L) version was produced for the commercial market. Both the 366 and 427 commercial versions were built with a raised-deck, four-bolt main bearing cap cylinder to accommodate an extra oil control ring on the pistons. Unfortunately, the raised deck design complicated the use of the block in racing applications, as standard intake manifolds required spacers for proper fit. Distributors with adjustable collars that allowed adjustments to the length of the distributor shaft also had to be used with 366 and 427 truck blocks.

Mark IV engines also found themselves widely used in power boats, a natural application for these robust power plants. Many of these engines were ordinary Chevrolet production models that were fitted with the necessary accessories and drive system to adapt them to marine propulsion. Mercury Marine, in particular, was a major user of the Mark IV in marine drives, and relabeled the engines with their corporate logo.

Generation V

General Motors changed from using the "Mark" designation to the "Generation" designation because Ford Motor Company owns the "Mark" naming rights as it was used on some Lincoln automobile models.

For 1991 General Motors made significant changes to the Big-Block resulting in the Generation V. The block received a one-piece rear seal and all blocks received 4-bolt mains. Additionally the main oil galley was moved from near the oil pan to near the camshaft. Also the valvetrain became non-adjustable and the provisions for a mechanical fuel pump were eliminated. Cast aluminum rocker covers were fitted in place of stamped steel covers.[27]


From 1991 the 454 was updated to the new Gen V block, crankshaft and heads. This engine was rated at 230 net hp, 380 ft lbs net torque, and was discontinued after 1995, GM coming out with the Vortec 7400 in 1996.


The Chevrolet 502 V8

The Chevrolet 502 V8

The 502—with a 501.28 cu in (8.2 L) total displacement—had a bore and stroke of 4.466 in × 4 in (113.4 mm × 101.6 mm) and a cast iron 4-bolt main block. GM offered it in their Performance Parts catalog, available as multiple crate motors with horsepower ratings from 338 to 600 hp (252 to 447 kW) and torque of 470 to 567 lb⋅ft (637 to 769 N⋅m) in "Base" and "Deluxe" packages.[28] The "Ram Jet 502",[29] the 496 hp (370 kW) / 565 lb⋅ft (766 N⋅m) crate motor, was offered with fuel injection, and came as a turn key setup which included all the wiring and electronics needed to operate in any vehicle. It was also used in marine applications.


General Motors began offering a newly developed 572 cu in (9.4 L) in 1998[30] to the aftermarket via its GM Performance Parts division. This engine has a bore and a stroke of 4.56 in × 4 3⁄8 in (115.8 mm × 111.1 mm). This is a 620 hp (462 kW) and 650 lb⋅ft (881 N⋅m) version, designated ZZ572/620 Deluxe, capable of running on 92 octane pump gasoline for street applications.[31] Another version of the same engine is available as a high compression variant, codenamed ZZ572/720R Deluxe, generating a minimum of 720 hp (537 kW) on high-octane, i.e., race-gas.[32]

Generation VI

Vortec 7400 (L29)

The Vortec 7400 L29 7.4 L (454 cu in) V8 was a truck version of the Chevrolet Big-Block engine. Introduced in 1996, it was produced for five years, until replaced by the Vortec 8100. Although introduced as the Vortec 7400 in 1996, it was basically a 454 Big-Block with a hydraulic roller cam, parts more suitable for use in light duty trucks, and more advanced technology. The engine had MPFI (multi-port fuel injection), which gave slightly more power and better fuel economy, and 2 valves per cylinder. The engine had a bore and stroke of 4 1⁄4 in × 4 in (108.0 mm × 101.6 mm), producing 290 hp (216 kW) at 4000 rpm and 410 lb⋅ft (556 N⋅m) at 3200 rpm.

L29 Applications:

  • 1996–2000 Chevrolet/GMC C/K GMT-400 platform trucks 2500 and 3500

  • 1996–1999 Chevrolet Suburban 2500/GMC Suburban 2500 (option)

  • 1996–2000 Chevrolet Express 3/4 or 1 ton

Vortec 7400 (L21)

The Vortec 7400 L21 was a commercial version of the Chevrolet Big-Block engine used in the medium duty truck platform. Its design shared much with the L29 454, but with the addition of forged pistons and crankshaft, and coil near plug ignition. It had slightly reduced power compared to the L29 454 and used a different PCM. The L21 was paired with the early 4 speed Allison automatic transmission or manual transmission, depending on the application.

L21 Applications:

  • 1998–2001 Chevrolet Kodiak/GMC TopKick/Isuzu H-Series 4500 5500

  • 1998–2001 Kodiak/Topkick

  • 1998–2001 P12 HD Motorhome Chassis. The Workhorse W-20 is a clone of the P12 Chassis.

Generation VII

Vortec 8100 (L18)

The Vortec 8100 L18 was a V8 truck engine. It was a redesigned Chevrolet Big-Block engine and was introduced with the 2001 full-size pickup trucks. It is an all-iron engine (block and heads) with two valves per cylinder. It retained the same bore diameter as the old 7.4 L (454 cu in) Big-Blocks, but the stroke was upped by 9.4 mm (0.37 in) to reach 496 cu in (8.1 L), for a total bore and stroke of 4 1⁄4 in × 4.37 in (108 mm × 111 mm). Power output ranged from 340 to 550 hp (254 to 410 kW), and torque from 455 to 690 lb⋅ft (617 to 936 N⋅m).

Other important differences between the Vortec 8100 and older Big Blocks include a changed firing order (1-8-7-2-6-5-4-3), a new 18-bolt head bolt pattern, longer connecting rods, different symmetrical intake ports, different oil pan rails and the use of metric threads throughout the engine. The fuel-injection system for the Vortec 8100 is nearly identical to that used on Gen III engines, right down to the fuel and spark tables in the ECU.[33]

Vortec 8100s were built at GM's Tonawanda Engine plant. The last L18 was manufactured in December 2009.

L18 Applications:

GM sold the Vortec 8100 to Workhorse (now a division of Navistar), making it one of the most popular engine choices in gas powered Class A motorhomes during the first decade of this century. GM stopped installing Big Block V8s in the Silverado HD trucks when the GMT-800 series was discontinued in 2007.

  • Chevrolet Silverado/GMC Sierra 2500HD & 3500HD (option)

  • Chevrolet Suburban/GMC Yukon XL 2500 (option)

  • Chevrolet Express 3/4 or 1 ton

  • Chevrolet Avalanche 2500 (std on GMT800 2500)

  • Chevrolet Kodiak

  • Workhorse Class A motorhomes.

  • T-98 Kombat armored vehicles.

  • U-Haul's 26-foot (7.9 m) truck.

  • Malibu Boats, e.g. Wakesetter.[34]

  • MasterCraft Boats


Many custom engine builders across the United States, as well as a large variety of aftermarket components manufactured for the Big Block family, make it possible to build a complete Big Block engine that contains no Chevrolet components. Blocks made of both iron and aluminum alloys, for many different purposes—e.g. street-use, racing, etc.—are available in stock or modified configurations, as well as with increased deck height to allow for a longer stroke or more favorable rod length ratios, depending on intent, providing the ability to make engines with capacities of 632-cubic-inch (10.4 L),[35] 798-cubic-inch (13.1 L),[36] and as large as 1,005.8-cubic-inch (16.5 L).[37]

See also

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

  • Buick V8 engine

  • Cadillac V8 engine

  • Chevrolet Small-Block engine

  • GMC V8 engine

  • Oldsmobile V8 engine

  • Pontiac V8 engine

  • Holden V8 engine

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

  • GM LT engine—Generation II small-block

  • GM LS engine—Generation III/IV small-block

  • List of GM engines

Competitors' equivalent offerings:


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