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Chevrolet Big-Block engine

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Chevrolet Big-Block engine

Scuderia Cazzani Chevrolet 1000 hp Offshore Racing Engine

The Chevrolet "Big Block" is a term for a series of large displacement V8 engines that were developed in the USA during the 1950s and 1960s. 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.

Generation 1: W-series

The first version of the "Big Block" V8 Chevrolet engine was introduced in 1958, and was also known as the "Single U" series. 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 cubic inches (5.7 L), available from 1958 to 1961 in cars, and in light trucks through 1964;
  • 409 cubic inches (6.702 L), available from 1961 to 1965; and
  • 427 cubic inches (6.9973 L), available in 1962 and 1963.

The W-series engine was made of cast iron, which was a common material in use at the time. 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-cubic-inch "Small Block" engines, the W-series valve gear consisted of tubular steel push rods 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 (revolutions per minute).

Unlike many of its contemporaries, 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 was 4.125 in (104.8 mm) and stroke was 3.25 in (82.6 mm), resulting in a substantially oversquare design. This engine was superseded by the 409-cubic-inch 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.

Model Name Features Power (Advertised Gross)
1958 1961 Turbo-Thrust 4 barrel 250 hp (190 kW)
1958 1961 Super Turbo-Thrust "Tri-Power" 3x2 barrel 280 hp (210 kW)
1958 1961 Special Turbo-Thrust 4 barrel 305 hp (227 kW)
1958 1960 Special Super Turbo-Thrust "Tri-Power" 3x2 barrel 315 hp (235 kW)
1959 1960 Special Turbo-Thrust 4 barrel 320 hp (240 kW)
1959 1961 Special Super Turbo-Thrust "Tri-Power" 3x2 barrel 335 hp (250 kW)
1960 1961 Special Turbo-Thrust 4 barrel 340 hp (250 kW)
1960 1961 Special Super Turbo-Thrust "Tri-Power" 3x2 barrel 350 hp (260 kW)


A 409-cubic-inch (6.7 L) version was Chevrolet's top regular production engine from 1961 to 1965, with a choice of single or dual four-barrel carburetors. Bore and stroke were both up from the 348 to 4.312 in (109.5 mm) by 3.50 in (88.9 mm). On December 17, 1960, the 409 engine was announced along with the [1]

In the 1963 model year, output reached 425 hp (317 kW) at 6200 rpm with the 2X4 setup, 11.25:1 compression and a solid lifter camshaft. This engine was immortalized in the Beach Boys song titled "409". The engine was available through mid-1965, when it was replaced by the 396-cubic-inch 425 hp (317 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 four-barrel cast-iron intake mounting a Rochester 4GC square-bore carburetor, and a hydraulic-lifter camshaft.

427 (Z11)

A special 427 cubic inches (7.00 L) version of the 409 engine was used in the 1963 Chevrolet Impala Sport Coupe, ordered under Chevrolet Regular Production Option (RPO) Z11.[2] This was a special package created for drag racers, and it consisted of an aluminum 427 engine and 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.[3] Unlike the later, second-generation 427, it was based on the W-series 409 engine, but with a longer 3.65 in (93 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 (320 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.

Generation 2: Mark IV Series

Development of the second generation Big-Block started with the so-called Mystery Motor (Mark II Z33 427) used in Chevrolet's 1963 Daytona 500 record-setting stock cars. This "secret" engine was a substantially modified form of the W-series engine, and was subsequently released for production use in mid-1965 as the Mark IV, referred to in sales literature as the "Turbo-Jet V8".

Where the Mark IV differed from the W-series engine was 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, 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 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. These features, along with the robust crankcase design, sturdy forged steel crankshaft and massive four-bolt main bearing caps used in the high performance versions, resulted in what many have considered to be the most rugged and reliable large displacement automotive V8 engine design of all time.


The 366 Big Block V-8 (6.0 L) gasoline engine was used only in Chevrolet medium duty trucks and in school buses. It had a bore of 3.935" and a stroke of 3.760". 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 only produced as a tall deck engine with a 0.400" deck, taller than the 396, 402, and 454 short-deck Big Blocks.

396 and 402

The 396-cubic-inch (6.5 L) V8 was introduced in the 1965 Corvette as the L78 option and in the Z16 Chevelle. It had a bore of 4.095 in (104.0 mm) and a stroke of 3.760 in (95.5 mm), and produced 375 hp (280 kW) and 560 lb·ft (760 N·m). This version of the 396 was equipped with four-bolt main bearing caps and was very comfortable with being operated in the upper 6000 rpm range.

Introduced in 1970, the 402-cubic-inch (6.6 L) was a 396-cubic-inch bored out by 0.030 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. The 402 label was used in light pickup trucks.

Power rating(s) by year:

  • 1965: 375 hp (280 kW)/425 hp (317 kW)
  • 1966: 325 hp (242 kW)/350 hp (260 kW)/360 hp (270 kW)/375 hp (280 kW)
  • 1967: 325 hp (242 kW)/350 hp (260 kW)/375 hp (280 kW)
  • 1968: 325 hp (242 kW)/350 hp (260 kW)/375 hp (280 kW)
  • 1969: 265 hp (198 kW)(2bbl)/325 hp (242 kW)/350 hp (260 kW)/375 hp (280 kW)
  • 1970: 330 hp (250 kW)/350 hp (260 kW)/375 hp (280 kW)
  • 1971: 300 hp (220 kW)
  • 1972: 240 hp (180 kW)

Used in:

396 and 402 Production codes

  • L-34: produced 1966-9, 10.25:1 compression, Holley ([4]
  • 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).[4]
  • 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).[4]
  • L-78: produced 1965-9, had 800 cfm Holley carburetor, 11:1 compression, forged pop-top pistons, aluminum high-rise intake manifold, steel crankshaft, solid lifter cam (same as the L-72; except in 1965 Z16 Chevelle), rectangular ("square") port closed chamber heads, and four-bolt main caps. It produced 375 hp (280 kW) in mid-size cars, 425 hp (317 kW) in Corvettes.[4]
  • 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 (250 kW) (1970), 300 hp (220 kW) (1971), 210 or 240 hp (160 or 180 kW) (1972 net horsepower, single or dual exhaust).[4]
  • L-34: produced 1970. Same as 396 ci L-34.
  • L-78: produced 1970. Same as 396 ci.


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

The highly successful and versatile 427-cubic-inch (426.7 cuin) (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 4.25 inches (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 horsepower (317 kW) version of the 427 - (RPO L72), resulting in a vehicle whose performance was the polar opposite of a taxi. This lightweight, big-block Biscayne was also commonly referred to as "Bisquick".

Perhaps the ultimate 427 for street applications was the 435 horsepower (324 kW) 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 three two-barrel carburetors (known as "Tri-Power"), in lieu of the L72's single four-barrel. Both engines used the same high lift, long duration, high overlap camshaft and large-port, cast-iron heads in order 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 zero to 60 miles per hour (97 km/h) times under 6 seconds and quarter-miles in the mid 13 second/106 MPH range for both the L72 and L71.

In 2011, Super Chevy Magazine conducted a chassis dyno test of a well documented, production-line stock, but well-tuned, L-72 "COPO" Camaro, and recorded only 287 peak HP at the wheels, demonstrating how exagerrated the old "gross" HP ratings actually were.[5]

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 Chaparral 2F and McLaren M8B. The ZL1 had specifications 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 total engine weight into small-block Chevrolet territory (approx. 575 lb or 261 kg dressed). The engine was also fitted with the new open combustion chamber cylinder heads, 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 and despite the "larger than life legends" surrounding it, actual engine dyno tests of a certified production line stock ZL1 revealed 376 SAE net HP, with output swelling to 524 Gross HP 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.[6] 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.[7]

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 quarter mile, which correlates quite well with the previously referenced 376 SAE Net HP figure. Super Stock and Drag Racing Magazine recorded an 11.62 second/122.15 MPH quarter mile 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 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, "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 $4718 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 (620 N·m).

Features Compression
Gross Power
1966 1969 L36 4-barrel 10.25:1 390 hp (290 kW)
1966 1969 L72 4-barrel + solid-lifters, more aggressive cam and high flow cylinder heads 11.00:1 425 hp (317 kW)[8]
1967 1969 L68 L36 with 3x2-barrel carbs. 10.25:1 400 hp (300 kW)
1967 1969 L71 L72 with 3X2 barrel carbs. 11.00:1 435 hp (324 kW)
1967 1969 L89 L71 + aluminum heads; RPO L89 also applied to L78 "375 HP" 396 engine with aluminum head option. 11.00:1 435 hp (324 kW)
1967 1969 L88 Racing-spec cam, high-flow aluminum heads (casting #s varied by model year) and some upgraded, competition-grade parts 12.50:1[9] 430 hp (320 kW)[10]
1969 1969 ZL1 Aluminum block with open chamber "3946074" aluminum heads; cam even "hotter" than L88's; upgraded parts similar to L88's 12.00:1 430 hp (320 kW)
1970 1977(?) ZLX L88-ZL1 hybrid; iron block with aluminum heads 12.25:1 430(?) hp (321 kW)


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).[11]
  • 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 full-size cars, 390 hp (290 kW) in Corvettes (by exhaust system).[11]
  • 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 (300 kW), and was used in Corvettes.[11]


The Big-Block was expanded again for 1970 to 453.96 cubic inches (7.4 L), with a 4.250 in (108.0 mm) bore and 4 in (100 mm) stroke. The 1970 Chevrolet Corvette LS5 version of this engine produced 390 hp (291 kW) and 500 lb·ft (680 N·m), and the LS6 engine was rated at 450 hp (340 kW). It has been suggested that the LS6 was substantially underrated and actually produced well over 500 horsepower (370 kW) as delivered from the factory, although there is no empirical evidence to support this claim. Indeed, the AHRA ASA (Showroom Stock Automatic) Class record-holding Chevelle LS6 for the 1970 season posted a best of season trap speed of 106.76 mph (171.81 km/h),[12] which suggests something on the order of 350 "as installed" (SAE Net) HP for a 3,900 pounds (1,800 kg) car and driver combination. Indeed, Super Chevy Magazine conducted a chassis dyno test of a well-documented, well tuned, but production-line stock 1970 LS6 Chevelle and recorded 283 peak HP at the wheels[5] - a figure that lines up quite well with the previously referenced 350 SAE Net HP figure.

A 465 hp (347 kW) and 610 lb·ft (830 N·m) version of the 454, dubbed LS7, was also designed but never went into production. However, a handful of LS7 intake manifolds were produced and sold by a few Chevrolet dealers as performance parts. The LS7 was later offered as a crate engine from GM and advertised at 500 Gross HP.

Power began falling off after 1970, with the 1971 LS5 producing 365 hp (272 kW) and 550 lb·ft (750 N·m), and the LS6 option coming in at 425 hp (317 kW) and 575 lb·ft (780 N·m). Only the LS5 remained in 1972, when SAE net power ratings and the move towards emission compliance resulted in a decline to 270 hp (200 kW) and 468 lb·ft (635 N·m). The 1973 LS4 produced 275 hp (205 kW) and 468 lb·ft (635 N·m), with 5 hp (3.7 kW) and 10 lb·ft (14 N·m) gone the following year. Hardened valve seats 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 until model year 1976.

GMC continued to use the 7.4 L (454 cu in) engine in their truck line, introducing a new Vortec 7400 version in 1996. GMC also introduced the 7.4 L 454 EFI in 1987 (GEN IV 1965-1990, GEN V 1990-1995, and GEN VI in 1996); the GEN prefix was used because Ford Motor Company owns the Mark V naming rights, since it was used on a Lincoln automobile between 1977–79, which had electronic fuel injection, giving more power and torque. The 454 EFI version was rated from 230 hp (170 kW) to 255 hp (190 kW) and from 385 lb·ft (522 N·m) to 405 lb·ft (549 N·m) of torque. The 7.4 L 454 EFI was found on GM 2500 and 3500 trucks made in 1987, until replaced with the Vortec 7400 (GEN VI) in 1996.


The Chevrolet 502 V8

The 502 had a bore of 4.466 with a stroke of 4.00 and a cast iron 4-bolt main block. GMC offered it in their Performance Parts catalog, available as multiple crate motors with horsepower ratings from 338 hp (252 kW) to 600 hp (447 kW), and torque of 470 lb·ft (637 N·m) to 567 lb·ft (769 N·m) in "Base" and "Deluxe" packages.[13] The "Ram Jet 502",[14] 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.


Chevrolet began offering a 572-cubic-inch (9.4 L) "crate motor" in 1998.[15] This was a 620 hp (462 kW) / 650 lb·ft (881 N·m) version capable of running on 92 octane street gasoline.[16] Another version of the same engine was available as a high compression variant generating 720 hp on race gas.

The aftermarket

The large variety of aftermarket components manufactured for the Big Block family makes it possible to build a complete Big Block engine that contains no Chevrolet components. Blocks made of both iron and aluminum alloys are available in stock or modified configurations as well as with increased deck height to allow longer stroke or more favorable rod length ratios, providing the ability to make 632-cubic-inch (10.4 L) engines (or larger).

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-cubic-inch (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.

Vortec 7400


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), and 2 valves per cylinder, which gave more power. The engine had a 107.95 millimetres (4.3 inches) bore, 101.6 millimetres (4.0 inches) stroke, and produced 290 hp (216 kW) at 4000 rpm and 410 lb·ft (556 N·m) at 3200 rpm.

L29 Applications:


The Vortec 7400 L21 was a 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:

Vortec 8100


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 had an all-iron engine (block and heads) with two valves per cylinder. It retained the same bore diamter as the old 7.4 L Big-Blocks, but the stroke was upped by 9.4 mm (0.4 in) to reach 8.1L (496cuin), for a total of 107.95 mm (4.3 in) bore and 111 mm (4.4 in) stroke. Power output ranged from 340 hp (254 kW) to 550 hp (410 kW), and torque from 455 lb·ft (617 N·m) to 690 lb·ft (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.[17]

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

L18 Applications:

The Vortec 8100 was the engine used in the largest U-haul, their 26-foot (7.9 m) truck. GM also 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 V-8's in the Silverado HD trucks when the GMT-800 series was discontinued in 2007.

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:

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

Competitors' equivalent offerings:


  1. ^ by the Auto Editors of Consumer Guide (2008-04-24). """HowStuffWorks "Chevy 409-cid V-8 Engine Overview. Retrieved 2012-05-31. 
  2. ^
  3. ^ [1]
  4. ^ a b c d e Guide to Muscle Cars Magazine, 2/87, p.62.
  5. ^ a b Hill, Patrick (February 1, 2011). "Chevrolet Muscle Car Dyno Wars". publisher=Super Chevy Magazine. Retrieved November 1, 2014. 
  6. ^ Glowacki, Bill; et al. (2014). "COPO 427: The Relentless Pursuit of Acceleration". CRG Research Report. Camaro Research Group. Retrieved November 1, 2014. 
  7. ^ 2nd ZL1 DYNO TEST
  8. ^ Chevrolet actually advertised this engine as 450 hp (340 kW) for a short period of time. There is speculation over whether this engine actually put out 450 Gross HP, or if this was a marketing oversight that was later corrected.
  9. ^ L88 had a 12.5:1 compression ratio with closed chamber heads except during the last half of 1969, when it had open chambered heads that yielded 12.0:1
  10. ^ L88 was rated for 430 hp (320 kW) at 5200 rpm. With stock exhaust manifolds and operation in the 6,800 rpm range, it was generally accepted that the engine was capable of producing in excess of 500 Gross HP with free-flowing (open) long tube headers.
  11. ^ a b c Guide to Muscle Cars Magazine, 2/87, p.63.
  12. ^ "1970 Chevelle 454 LS6". Retrieved November 1, 2014. 
  13. ^ "2008 Crate Engine Catalog (p.25)" (PDF). Retrieved 2012-05-31. 
  14. ^ "Ram Jet 502 overview". Retrieved 2012-05-31. 
  15. ^ Freiburger, David (June 2004). "King Crate". Hot Rod. 
  16. ^ "ZZ 572/620 specifications". Retrieved 2012-05-31. 
  17. ^ "Automotive Repair Questions - TPI - Car Craft Magazine". Retrieved 2012-01-25. 


  • Peter C Sessler (1999). Ultimate American V8 Engine Data Book. MotorBooks/MBI Publishing Company.  
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