Chevrolet big-block engine

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 This engine was superseded by the 409 cu in (6.7 L) as Chevrolet's top performing engine in 1961 and went out of production for cars at the end of that year.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 338 hp (252 kW) when equipped with triple two-barrels.

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 × 3.5 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 aluminium intake manifold and two Carter AFB carburetors. It had a forged steel crankshaft.[14] 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.[15] 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 to 1965, with a single 4-barrel cast iron intake mounting a Rochester 4GC square-bore carburetor, and a hydraulic-lifter camshaft.

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.[16] This was a special package created for drag racers, as well as NASCAR,[17] and it consisted of a 427 cu in (7.0 L) engine with aluminium body parts, and a cowl-induction air intake system. The aluminium body parts were fabricated in Flint, Michigan at the facility now known as GM Flint Metal Center.[18] 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 aluminium 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). Fifty 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. There is no evidence from GM that shows 57 cars were built.

The 366 cu in (6.0 L) Big Block V-8 gasoline engine was used in Chevrolet medium duty trucks, school buses and police sedans. 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 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 0.4 in (10 mm) taller than the 396, 402, and 454 short-deck Big Blocks.

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 × stroke of 4.094 in × 3.760 in (104 mm × 95.5 mm),[26][27] and produced 375 bhp (380 PS; 280 kW) at 5600 rpm and 415 lb⋅ft (563 N⋅m) of torque at 3600 rpm.[28] 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 being 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: 325 hp (242 kW)/375 hp (280 kW)/425 hp (317 kW)
• 1966: 325 hp (242 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: 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

Applications:

• 1965 Chevrolet Corvette
• 1965–1972 Chevrolet Chevelle
• 1967–1972 Chevrolet Camaro
• 1968–1970 Chevrolet Nova
• 1970–1972 Chevrolet Monte Carlo, Chevrolet El Camino, GMC Sprint, Chevrolet trucks
• 1965–1972 Chevrolet Biscayne, Chevrolet Bel Air, Chevrolet Impala, Chevrolet Impala SS, Chevrolet Caprice

396 and 402 production codes:

396

• L-34: produced 1966–69, 10.25:1 compression, Holley (Q-jet 1968–1969) 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).[29]
• L-35: produced 1965–69, 10.25:1 compression, Q-jet carburetor, forged steel (1965–67) or nodular iron (1968–69) crankshaft, hydraulic lifters, oval port closed chamber heads, and two-bolt main caps. It produced 325 hp (242 kW).[29]
• L-37: produced 1965, 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).[29]
• L-78: produced 1965–69, had a Holley 800 cu ft/min (23 m³/min) carburetor, compression ratio 11:1, forged pop-top pistons, aluminium 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.[29]

402

• LS-3: produced 1970–72, 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).[29]
• L-34: produced 1970. Same as 396 cu in (6.5 L) L-34 from 1967 to 1969.
• L-78: produced 1970. Same as 396 cu in (6.5 L) L-78 from 1966 to 1969.

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 3×2-barrel Holley carburetors,[30] 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.[31][32]

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).[33]

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 with the RPO ZL1 engine package was built in early December 1968 and featured aluminum closed chamber heads shared with the L88. Both L88 and ZL1 optioned cars continued to be built with closed chamber heads until approximately March 1969, when the open combustion chamber aluminum heads finally were in production and began being fitted to the L88 and ZL1 engines. The ZL1 engine also featured a lightweight 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.[34] 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.[35]

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 1969 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).

Applications:

• 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).[36]
• L-36: produced 1966–69, 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).[36]
• L-68: produced 1967–69, 10.25:1 compression, Tri-Power, nodular iron crankshaft, hydraulic lifters, aluminium oval port closed chamber heads, and two-bolt main caps. It produced 400 hp (298 kW), and was used in Corvettes.[36]

454 in a 1970 Chevelle SS

For 1970, the Big-Block was expanded again, to 454 cu in (7.4 L), with a bore × stroke of 4+1⁄4 in × 4 in (108.0 mm × 101.6 mm). The 1970 Chevrolet Corvette LS-5 version of this engine was factory-rated at 390 bhp (395 PS; 291 kW) and 500 lb⋅ft (678 N⋅m), and the LS-6 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.[37][38]

It has been suggested that the LS-6 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),[39] 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[33] – 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, which is an LS7). 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
• 1971–1975 GMC Sprint
• 1970–1974 Chevrolet Corvette

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 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. The 1991–1993 454SS made 255 horsepower at 4000 rpm and 405 lb-ft of torque at 2400 rpm thanks to dual 2.5" catalytic converters. All other versions, including the 1990 SS, made 230 horsepower at 3600 rpm and 385 lb-ft of torque at 1600 rpm through a single 3" catalytic converter.

• 1987–1990 Chevrolet R2500 and R/V3500
• 1988–1990 Chevrolet C/K
• 1989–1990 Chevrolet/GMC 3500 van

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. 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.

The 366 cu in (6.0 L) truck engine also received the Mark V updates for 1991.[41]

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

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.[42] The "Ram Jet 502,"[43] 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[44] 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.[45] 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 racing fuel.[46] The 572 is officially offered by Chevrolet for the 2022 model year COPO Camaro.[47][48][49]

In 2021, Chevrolet Performance presented the largest and most powerful crate engine in the brand's history—the ZZ632/1000 crate engine. It is a naturally-aspirated, 632 cu in (10.4 L) V8, producing 1,004 hp (749 kW) and 876 lb⋅ft (1,188 N⋅m) of torque.[50] The motor itself weighs 680 lb (310 kg).[51]

According to Russ O'Blenes, the GM director of the Performance and Racing Propulsion Team, the ZZ632 is the "biggest, baddest crate engine we've ever built. [It] sits at the top of our unparalleled crate engine lineup as the king of performance. It delivers incredible power, and it does it on pump gas."[52]

The Big Block V8 reaches peak power at 6,600 rpm, and revs to a recommended maximum of 7,000 rpm. Fuel is delivered through eight-port injectors, with the engine breathing through CNC-machined high-flow aluminum cylinder heads featuring symmetrical ports. While Big Blocks have usually been designed with variations in port shape from cylinder to cylinder, all eight intake ports of the ZZ632 have the same volume, length, and layout. Furthermore, all of the ZZ632's exhaust ports are identical. This arrangement guarantees all individual cylinders produce similar power.[53]

These RS-X symmetrical port cylinder heads are named for powertrain engineer Ron Sperry, who designed them as one of his final accomplishments in more than 50 years working on General Motors performance and racing engines. Sperry also introduced symmetrical ports to Chevy's iconic Small Block V-8, with the Gen III LS1 engine that debuted in the 1997 Chevrolet Corvette.

The ZZ632's iron block shares a mold with Chevrolet Performance's ZZ572 crate engines, but the castings are machined to accommodate the huge 632 cubic-inch displacement. The bore grows by 0.040 in (1.0 mm), compared to the 572-cubic-inch V8s, with most of the displacement gain coming from a stroke that is 0.375 in (9.5 mm) longer. To provide clearance for that long-stroke, engineers modified both the block and the connecting rods. Four-bolt main caps and a forged rotating assembly assure strength and durability. During development, a single engine endured more than 200 simulated drag strip passes on a dynamometer.

The ZZ632/1000 crate engine is slated to be on display at the 2021 SEMA Show in Las Vegas, November 2–5. Chevrolet Performance dealers will begin deliveries in early 2022.[54]

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 trucks, and more advanced technology. The engine had MPFI (multi-port fuel injection), which gave slightly more power and better fuel economy, and two 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 C/K / GMC Sierra 2500, 3500, and C3500HD (above 8,500 pounds GVWR)
• 1996–1999 Chevrolet/GMC Suburban 2500
• 1996–2000 Chevrolet Express/GMC Savana 3500

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 and 5500
• 1998–2001 P12 HD Motorhome Chassis. The Workhorse W-20 is a clone of the P12 Chassis.

The Vortec 8100 L18 is a big-block V8 engine primarily used as a 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 4.25 in (107.95 mm) bore diameter of the old 7.0 L (427 cu in) and 7.4 L (454 cu in) big-blocks, but the stroke was increased to 4.37 in (111.00 mm) for a total displacement of 495.95 cu in (8.1 L). Power output ranged from 210 to 340 hp (157 to 254 kW), and torque from 325 to 455 lb⋅ft (441 to 617 N⋅m).[55][56][57][58][59][60]

Other important differences between the Vortec 8100 and older big-blocks include a changed firing order. The firing order of older big-block engines is 1-8-4-3-6-5-7-2[61] while Vortec 8100's firing order is 1-8-7-2-6-5-4-3. Other upgrades of Vortec 8100 include 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 small block engines, right down to the fuel and spark tables in the ECU.[62]

GM sold the Vortec 8100 to Workhorse (now a division of Navistar), making it one of the most popular engine choices in gasoline-powered Class A motorhomes during the early 2000s. GM stopped installing big-block V8s in the Silverado HD trucks when the GMT800 series was discontinued in 2007.

Vortec 8100s were built at GM's Tonawanda Engine plant while the engine block and cylinder head were cast at Saginaw Metal Casting Operations. The last L18 was manufactured in December 2009.

L18 applications:

• 2001–2002 Chevrolet/GMC C3500HD
• 2001–2007 Chevrolet Silverado/GMC Sierra 2500HD and 3500 (option)
• 2001–2006 Chevrolet Suburban/GMC Yukon XL 2500 (option)
• 2001–2002 Chevrolet Express/GMC Savana 3500
• 2002–2006 Chevrolet Avalanche 2500 (standard)
• 2001–2010 Chevrolet Kodiak/GMC TopKick (including U-Haul's 26-foot (7.9 m) truck)
• Workhorse Class A motorhomes
• T-98 Kombat armored vehicles
• Malibu Boats, including the Wakesetter[63]
• MasterCraft Boats