The Junkyard LS Swap Guide: Which GM V8s to Pull, How to ID Them, What Else You Need

Every LS swap story starts in roughly the same place: a wrecked truck in a salvage yard with an engine that still turns over by hand. GM built its third and fourth generation small-block V8s in enormous numbers and put them in everything from half-ton pickups and vans to Corvettes, which is why the LS became the default answer for a Nova, a square body, a Miata or a 240Z. The trick is knowing exactly what you are looking at before you pay for it, and knowing what the engine does not come with.

This guide covers the engines worth hunting, how to confirm what is in front of you, how GM rated them, and the supporting parts that turn a long block into a running car. One rule up front: GM's ratings changed with model year, vehicle and transmission, so always look up the figure for the exact donor.

Start with the VIN, not the valve covers

On a complete donor, the eighth character of the VIN is the engine code. Summit Racing and PSI Conversion both publish tables that map that character to GM's RPO engine codes, and it is the fastest way to sort a row of trucks. The catch is that the VIN only tells you what the vehicle left the factory with. Summit points out that if the code does not match what you see under the hood, the engine may have been swapped at some point.

Read the code against the vehicle type and generation, because GM reused letters. A U is an LQ4 in a Gen III truck but an LS2 in a Gen IV car. A T is an LM7 in a Gen III truck but a supercharged LS9 in a Gen IV car. A J is an L99 Camaro engine in one table and an LY5 5.3 truck engine in another.

• T: LM7 5.3L, iron block, Gen III truck
• B: L33 5.3L, aluminum block, Gen III truck
• U: LQ4 6.0L, iron block, Gen III truck
• N: LQ9 6.0L, iron block, Gen III truck
• K: LY6 6.0L, iron block, Gen IV truck
• 8: L92 6.2L, Gen IV truck
• G: LS1 5.7L, Gen III car
• S: LS6, Gen III car
• W: LS3 6.2L, Gen IV car
• J: L99, Gen IV car

Once the engine is out of the vehicle, the VIN is no help, and the 6.0 truck engines show why. Summit notes the LQ4 and LQ9 are identical from the outside. The difference is inside: the LQ4 uses dished pistons, the LQ9 uses flat tops for more compression. Confirming a loose engine means pulling a cylinder head or running a borescope down a spark plug hole.

The engines worth hunting

LM7 5.3L: the default

The iron-block 5.3 with aluminum heads went into a huge range of GM trucks and SUVs from 1999 to 2007: Silverado and Sierra 1500s, Tahoes, Yukons, Suburbans, Avalanches and Express and Savana vans among them. Ratings moved with model year, from 270 to 295 hp and 315 to 335 lb-ft. It is heavy compared with the aluminum engines, but it is everywhere, which keeps prices sane and parts plentiful.

L33 5.3L: the aluminum one

The L33 is the 5.3 people walk past. It used an aluminum block with cast-in cylinder liners and was rated at 310 hp at 5,200 rpm and 335 lb-ft at 4,000 rpm. Production ran from 2005 to 2007, and it was offered only in four-wheel-drive Silverado and Sierra 1500s, most often reported as extended-cab, standard-bed trucks, so it takes patience to find one. VIN code B is the tell.

LQ4 and LQ9 6.0L: the boost candidates

The LQ4 arrived in 1999 and ran through 2007 in heavy-duty pickups, Suburbans and Yukon XLs, Express and Savana vans and the Hummer H2. Summit lists it at 364 cubic inches, with a 4.000 inch bore, 3.622 inch stroke and 9.4:1 compression, and output in the low 300 hp range depending on application. The LQ9 is the high-output version: flat-top pistons, 10.1:1 compression and 345 hp with 380 lb-ft, found in the Cadillac Escalade family, the Silverado SS, the Sierra Denali and the Classic VortecMax trucks from 2002 to 2007. Summit puts the iron 6.0 block at 216 lb, about 100 lb heavier than an aluminum LS1 block, but it is the block builders reach for when a turbo is in the plan.

One trap: Summit says 1999 and 2000 LQ4s used cast-iron cylinder heads and a 1.250 inch thick rear crankshaft flange, while later LQ4 and LQ9 engines have aluminum heads and a 0.857 inch flange. That flange difference matters when you mate the engine to a flexplate or flywheel.

LY6 6.0L: the Gen IV truck engine

The LY6 replaced the LQ4 and LQ9 for 2007. It brought variable valve timing and rectangle-port heads in the style of the L92 and LS3, and it was rated at 360 hp at 5,400 rpm and 380 lb-ft at 4,200 rpm. It lived in heavy-duty Silverado and Sierra pickups, three-quarter-ton Suburbans and Yukon XLs and full-size vans. Summit notes the block has internal oil passages for Active Fuel Management even though the LY6 never used it, and that its successor, the flex-fuel L96, is essentially the same engine.

L92 6.2L: the truck 6.2

The aluminum 6.2 L92 debuted in the 2007 Escalade with variable valve timing and was rated at 403 hp. It also powered Yukon Denali and Sierra Denali models, and a closely related version, the L9H, went into some Silverado and Sierra 1500s. These turn up less often than the 5.3 and 6.0, and they are priced like it.

LS1 and LS6: the original car engines

The LS1 was introduced in the 1997 Corvette and went on to the 1998 to 2002 Camaro and Firebird and the 2004 Pontiac GTO. It is an aluminum 5.7 liter, and its rating depended heavily on platform: 345 to 350 hp in the C5 Corvette, 305 to 310 hp in the Camaro Z28, 320 to 325 hp in the Camaro SS and 350 hp in the GTO. The LS6 was the Corvette Z06 engine from 2001 to 2004, rated 385 hp in its first year and 405 hp after that, and it also powered the 2004 and 2005 Cadillac CTS-V at 400 hp.

LS3 and L99: the 6.2 car engines

The LS3 is an aluminum 6.2 with a 4.065 inch bore that arrived in the 2008 Corvette at 430 hp and 424 lb-ft in base form, and it went into manual-transmission Camaro SS models from 2010 to 2015. Automatic Camaro SS cars got the L99 instead, rated at 400 hp and 410 lb-ft, with Active Fuel Management and variable valve timing. Wrecked fifth-generation Camaros are where most salvage-yard 6.2s come from.

What the engine does not come with

A long block is roughly half the job. Plan for these before you strip the donor, because some are far easier to pull from the wreck than to buy later.

• Wiring and computer. Gen III engines (LS1, LS6 and 4.8, 5.3 and 6.0 truck engines through 2006) use a 24-tooth crank reluctor and typically run P01 or P59 controllers. Most Gen IV engines (LS3, LS7, L76, L92, later LS2s and 2007 and later truck engines) use 58 teeth, but early LS2s, such as the 2005 Corvette and 2005 to 2006 GTO, used the 24-tooth wheel, and typically run E38 or E67 controllers. PSI Conversion warns that the engine, harness and controller must all match, and that a 24x harness on a 58x engine will crank but never fire.
• Throttle. According to PSI, 24x engines can run a cable throttle or drive-by-wire with factory electronics, while 58x engines only work with drive-by-wire when you stay with OEM controls. Take the pedal assembly with you.
• Transmission control. On 24x engines, one PCM can handle both the engine and an electronically controlled automatic. On 58x engines you typically need a separate transmission controller, with the 6L80 and 6L90 as the exception.
• Oil pan. LSX Magazine notes that factory pans usually do not fit swap chassis because of frame and steering linkage interference. Swap pans such as Chevrolet Performance's Muscle Car pan (5 quarts) and Holley's 302 series address that, and each lists a maximum crankshaft stroke.
• Mounts, headers and accessory drive. These are chassis-specific. Coordinated kits exist for popular platforms; Holley and Hooker's 1973 to 1987 C10 and C20 system, for example, bundles brackets, crossmember, headers, oil pan and an accessory drive designed to work together.

Gotchas that bite first-timers

• Same displacement, different engine. A 5.3 can be an iron LM7 or an aluminum L33, and two 6.0s that look identical can carry different pistons. Verify before you pay a premium.
• Mixing generations. A Gen IV engine and a Gen III computer do not talk without help. PSI notes that a conversion box can let a 24x controller read a 58x signal, but going the other way means changing the reluctor and timing components.
• Sensor colors as a quick check. PSI says the crank sensor above the starter has a black connector on 24x engines and a gray connector on 58x engines, and the cam sensor moves from the back of the block on 24x engines to the front timing cover on 58x engines.
• Swapped donors. A VIN match is only as reliable as the vehicle's history.
• Stroke limits. If a stroker is in the future, check the oil pan's stroke rating now.
• Early LQ4 flange. A 1999 or 2000 LQ4 needs flexplate or flywheel hardware that matches its thicker crank flange.

Done in a hurry, a junkyard swap becomes a garage full of parts that do not talk to each other. Read the code, pull the computer and harness with the engine, and match every electronic piece to the block's generation before you turn a wrench on the car.