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.

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:
The W-series engine was made of cast iron. The engine block had bore centers, two-bolt main bearing caps, a "side oiling" lubrication system, 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 "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 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 US 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, depending on the type of intake manifold and carburetion systems present.

348

The first iteration of the W-series engine was the 1958 "Turbo-Thrust", originally intended for use in Chevrolet trucks but also introduced in the larger, heavier 1958 passenger car line. Bore and stroke was, resulting in a substantially oversquare design. This engine was superseded by the 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. A special "Tri power" triple-two-barrel version, called the "Super Turbo-Thrust", produced. A "Special Turbo-Thrust" further upped the power output to with a single large four-barrel carburetor. Mechanical lifters and triple two-barrel carburetors brought the "Special Super Turbo-Thrust" up to. For 1959 and 1960, high-output versions of the top two engines were produced with and respectively. In 1961, power was again increased to for the single four-barrel model, and when equipped with triple two-barrels.
First YearLast YearModel NameFeaturesPower
19581961Turbo-Thrust4 barrel
19581961Super Turbo-Thrust3x2 barrel
19581961Special Turbo-Thrust4 barrel
19581960Special Super Turbo-Thrust3x2 barrel
19591960Special Turbo-Thrust4 barrel
19591961Special Super Turbo-Thrust3x2 barrel
19601961Special Turbo-Thrust4 barrel
19601961Special Super Turbo-Thrust3x2 barrel

409

A 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 to. On December 17, 1960, the 409 engine was announced along with the Impala SS model. The initial version of the engine produced with a single 4-barrel Carter AFB carburetor. The same engine was upped to in 1962. A 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. This dual-quad version was immortalized in the Beach Boys song titled "409".
In the 1963 model year, output reached @ 6000 rpm and @ 4200 rpm of torque with the Rochester 2X4-barrel carburetor setup, a compression ratio of 11:1 and a solid lifter camshaft. The engine was available through mid-1965, when it was replaced by the Mark IV big-block engine. In addition, a 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 version of the 409 engine was used in the 1963 Impala Sport Coupé, ordered under Chevrolet Regular Production Option Z11. This was a special package created for drag racers, as well as NASCAR, and it consisted of a 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. Unlike the later, second-generation 427, it was based on the W-series 409 engine, but with a longer 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 and. 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 engine produced for the 1963 season. Development began with a version and ended with a variant; however only the engine 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, 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 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.

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, 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, the "rat motor", as it was later nicknamed, was slightly heavier than the W-series model, with a dry weight of about. 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 of with a larger main bearing dimension, increased from the of the older engine. Like its predecessor, the Mark IV used crowned pistons, which were castings for conventional models and impact extruded, 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.

366

The 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. This engine was made from the 1960s until 2004.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 taller than the 396, 402, and 454 short-deck Big Blocks.

396 and 402

The 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, and produced at 5600 rpm and of torque at 3600 rpm. 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.
Introduced in 1970, the was a bored out by. Despite the fact that it was 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 by year:
Used in:
396 and 402 Production codes
The highly successful and versatile 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, 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 version of the 427 -.
Perhaps the ultimate 427 for street applications was the at 5800 rpm and 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 L72 427, but was fitted with 3X2-barrel Holley carburetors, 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 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- in 5.6 seconds and Dragstrip| in 13.8 second at range for both the L72 and L71.
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 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 does not equate to SAE net HP.
The RPO L89 was an L71 fitted with aluminum heads. While this option produced no power advantage, it did reduce engine weight by roughly. 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, 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 fuel, used an unshrouded radiator, and had poor low speed idle qualities - all of which made the two engines largely unsuitable for street use.
As impressive as the ZL1 was in its day, actual engine dyno tests of a certified production line stock ZL1 revealed SAE net with output swelling to 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. A second engine dyno test conducted on a second production line stock ZL1 revealed nearly identical figures for the various "gross" conditions.
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/, which correlates quite well with the previously referenced SAE Net figure. Super Stock and Drag Racing Magazine recorded an 11.62 second/ 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 trap speed indicated low 11-second ET potential and suggested something on the order of, "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 and 69 Camaros 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 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.
First
Year		Last
Year		Engine
Code		FeaturesCompression
ratio		Factory
Gross Power
Rating
19661969L364-barrel10.25:1
19661969L724-barrel + solid-lifters, more aggressive cam and high flow cylinder heads11.00:1
19671969L68L36 with 3×2-barrel carbs.10.25:1
19671969L71L72 with 3×2 barrel carbs.11.00:1
19671969L89L71 + aluminum heads; RPO L89 also applied to L78 "375 HP" 396 engine with aluminum head option.11.00:1
19671969L88Racing-spec cam, high-flow aluminum heads and some upgraded, competition-grade parts12.50:1
19691969ZL1Aluminum block with open chamber "3946074" aluminum heads ; cam even "hotter" than L88's; upgraded parts similar to L88's12.00:1
19701977ZLXL88-ZL1 hybrid; iron block with aluminum heads12.25:1

Notes:
427 Production codes
For 1970, the Big-Block was expanded again, to, with a bore x stroke of. The 1970 Chevrolet Corvette LS5 version of this engine was factory-rated at and, and the LS6 engine equipped with a single 4-barrel Holley carburetor was upgraded to at 5600 rpm and at 3600 rpm of torque.
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 as delivered from the factory. Indeed, the AHRA ASA Class record-holding Chevelle LS-6 for the 1970 racing season posted a best-of-season trap speed of, which suggests something on the order of 350 "as installed" HP for a 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 – a figure that lines up quite well with the previously referenced 350 SAE Net HP figure.
An even more powerful version, producing and, of the 454, then dubbed LS-7, 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 Gross.
In 1971, the LS-5 produced and, and the LS-6 option came in at and. 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 and. The 1973 LS-4 produced and, with and 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.
General Motors introduced EFI in 1987, which was found on GM C1500 SS, C/K2500 and C/K3500 trucks. The 454 EFI version was rated from to and from to of torque.
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. In addition to the 427, a 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.

L19

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.

502

The 502—with a total displacement—had a bore and stroke of 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 and torque of in "Base" and "Deluxe" packages. The "Ram Jet 502", the / 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.

ZZ572

General Motors began offering a newly developed in 1998 to the aftermarket via its GM Performance Parts division. This engine has a bore and a stroke of. This is a and version, designated ZZ572/620 Deluxe, capable of running on 92 octane pump gasoline for street applications. Another version of the same engine is available as a high compression variant, codenamed ZZ572/720R Deluxe, generating a minimum of on high-octane, i.e., race-gas.

Generation VI

Vortec 7400 (L29)

The Vortec 7400 L29 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, which gave slightly more power and better fuel economy, and 2 valves per cylinder. The engine had a bore and stroke of, producing at 4000 rpm and at 3200 rpm.
L29 Applications:
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:

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 with two valves per cylinder. It retained the same bore diameter as the old Big-Blocks, but the stroke was upped by to reach, for a total bore and stroke of. and torque from.
Other important differences between the Vortec 8100 and older Big Blocks include a changed firing order, 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.
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, 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.
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,, and as large as.

Footnotes

Citations