Chevrolet LC9 Specifications
| Engine Model: Chevrolet LC9 |
| Engine Type: 4-cycle 8-cylinder AFM VVT liquid-cooled gasoline |
| Total Displacement: 325 cu.in (5.32 L) |
| Rated Engine Power: 315-320 Hp (233-237 kW) at 5400 rpm |
| Fuel System Type: Sequential multi-port fuel injection |
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The Chevrolet LC9 is a 5.3-liter V8 engine produced by
General Motors as a cornerstone of the Gen IV LS small-block family from 2007
through 2014. Engineered for full-size trucks and SUVs, the LC9 distinguishes
itself as the flex-fuel capable, aluminum-block counterpart to the iron-block
LH6. Its primary design mandate balanced robust power delivery with reduced
weight, utilizing an aluminum cylinder block to enhance vehicle dynamics and
fuel efficiency.
The LC9 represents a significant evolution in GM’s small-block lineage,
incorporating advanced technologies such as Active Fuel Management (AFM) for
cylinder deactivation and, in later iterations, Variable Valve Timing (VVT).
This engine was calibrated to operate seamlessly on gasoline or E85 ethanol
blends, providing a versatile powertrain solution across a wide range of GM’s
light-duty truck and SUV platforms.
The LC9 is a 90-degree V8 engine with a displacement of 5.3 liters, equivalent
to 325 cubic inches (5,328 cc). The bore and stroke dimensions are 96.01 mm
(3.780 in) by 92.0 mm (3.622 in), utilizing a square architecture that favors
mid-range torque production. The compression ratio varied by model year: engines
from 2007 through 2009 utilized a 9.9:1 ratio, while units produced from 2010 to
2011 featured a reduced compression ratio of 9.6:1 to accommodate the
introduction of VVT and revised combustion parameters.
Power output was contingent upon fuel type and vehicle application. On gasoline,
the LC9 produced between 315 and 320 horsepower at 5,200 to 5,400 rpm, with
torque figures ranging from 335 to 338 lb-ft at 4,000 to 4,400 rpm. When
operating on E85 ethanol, output increased marginally to a maximum of 326
horsepower at 5,300 rpm, with torque remaining consistent with gasoline ratings.
The engine employed a firing order of 1-8-7-2-6-5-4-3. The valvetrain
configuration is a pushrod overhead valve (OHV) design with two valves per
cylinder, actuated by hydraulic roller lifters to minimize maintenance and
reduce friction.
The cylinder block is constructed from cast aluminum, a
significant departure from traditional iron blocks that reduced overall engine
mass by approximately 40.8 kg (90 lbs). The block features a deep-skirt design
with six-bolt main bearing caps - four vertical and two cross-bolts per cap -
providing exceptional structural rigidity under high cylinder pressures.
Cylinder bores were cast using a press-fit iron liner to ensure durability and
proper piston ring sealing. The engine utilized a 58X crankshaft position
reluctor wheel, a high-resolution system that allowed for more precise ignition
and fuel injection control compared to earlier 24X systems. The block
accommodated the AFM system, which required specific oil galleries and valley
cover provisions for the solenoid-actuated lifters that controlled cylinder
deactivation.
The LC9 is equipped with cast aluminum cylinder heads,
commonly bearing casting numbers 799 or 243, depending on the production year
and vehicle platform. These heads are characterized by “cathedral” shaped intake
ports, a design optimized for a broad torque curve and high airflow velocity.
The intake valves measure 50.8 mm (2.00 in) in diameter, while the exhaust
valves are 38.1 mm (1.55 in).
Both valves are actuated by a roller rocker arm system with a 1.7:1 ratio. In
applications featuring VVT, the cylinder heads were adapted to accommodate a
camshaft phaser on the front of the engine, allowing the electronic control
module to adjust camshaft timing relative to the crankshaft by up to 62 deg. The
valve springs were selected for durability under AFM operation, which
experiences varied load cycles during cylinder reactivation.
The fuel system is a sequential multi-port fuel
injection (SFI) design, featuring a returnless fuel rail to reduce evaporative
emissions and fuel heating. The LCJ RPO code designation for the flex-fuel
system included specific injectors, fuel lines, and a fuel composition sensor
that continuously monitored the ethanol content in the fuel, automatically
adjusting spark timing and air-fuel ratio for optimal performance and emissions.
All LC9 engines were equipped with an aluminum intake manifold with a composite
design to reduce weight and heat soak. The fuel system operated at a nominal
pressure of 400 to 450 kPa (58 to 65 psi). For applications with VVT, the
fueling strategy was further refined to leverage the broader torque band enabled
by variable cam timing.
The lubrication system is a full-pressure, gerotor-type
oil pump driven directly by the crankshaft. System capacity, including the oil
filter, is 5.7 liters (6.0 quarts). The oil pump was calibrated to maintain a
pressure of 276 kPa (40 psi) at hot idle and 414 kPa (60 psi) at operating
speeds. A critical component of the LC9’s lubrication architecture was the AFM
oil manifold assembly, which housed four solenoids responsible for directing oil
pressure to the eight active fuel management lifters.
This system required the use of a specific oil filter and a high-efficiency oil
pan baffle to ensure consistent oil pressure under dynamic driving conditions,
particularly during the transition between V8 and V4 modes. The recommended
engine oil viscosity is 5W-30 meeting GM dexos1 specifications.
The cooling system utilizes a belt-driven water pump
mounted to the front of the engine, circulating coolant through the aluminum
block and heads. The system’s capacity, including the radiator, is approximately
14.2 liters (15.0 quarts). Thermostat regulation is provided by a wax-pellet
thermostat that begins to open at 90°C (194°F) and is fully open at 104°C
(219°F).
The engine uses a reverse-flow cooling design where coolant is directed to the
cylinder heads first, then to the block, reducing detonation sensitivity and
allowing for a higher compression ratio. The aluminum construction of the engine
necessitated the use of Dex-Cool (OAT) extended-life coolant to prevent galvanic
corrosion within the cooling passages.
The engine features a stainless steel exhaust manifold
with a single or dual exhaust outlet configuration depending on the vehicle
platform. The manifolds integrate provisions for the air injection reaction
(AIR) system on certain applications, which injects secondary air into the
exhaust stream during cold starts to rapidly heat the catalytic converters.
The LC9 employs a coil-near-plug ignition system with
individual ignition coils mounted directly above each spark plug, eliminating
high-tension spark plug wires. Spark plug gap is specified at 1.02 mm (0.040
in). The system is triggered by the 58X crankshaft position sensor and a single
camshaft position sensor, providing precise ignition timing data to the engine
control module.
Active Fuel Management (AFM): This system deactivates
four cylinders (numbers 1, 7, 6, and 4) under light-load conditions.
Deactivation is achieved via specialized lifters that collapse, preventing the
valves from opening while the fuel injectors for those cylinders are
simultaneously turned off. Transition between V8 and V4 modes is seamless,
controlled by the engine control module based on throttle position, engine load,
and vehicle speed.
Variable Valve Timing (VVT): Introduced in 2010, this system used a camshaft
phaser that could adjust camshaft position up to 50 deg of rotation. This
allowed for optimized overlap and valve event timing across the engine’s entire
operating range, improving low-end torque, high-end power, and fuel efficiency
while reducing emissions.
The LC9 engine, when fully dressed, has a length of 724
mm (28.5 in), a width of 673 mm (26.5 in), and a height of 711 mm (28.0 in). The
dry weight of the engine, without accessories, is 188 kg (415 lbs).
Spark Plugs: The recommended spark plug is an
iridium-tipped plug with a service interval of 161,000 km (100,000 miles). The
gap is non-adjustable but must be verified at 1.02 mm (0.040 in).
Engine Oil: The oil capacity with filter is 5.7 liters (6.0 quarts). The oil
change interval is 7,500 miles or one year under normal driving conditions, with
severe service intervals reduced to 5,000 km (3,000 miles). Dexos1-certified
5W-30 synthetic blend or full synthetic oil is required.
Coolant: The system capacity is 14.2 liters (15.0 quarts). Dex-Cool (OAT) orange
coolant must be used, with a replacement interval of 5 years or 240,000 km
(150,000 miles).
Air Filter: Engine air filter replacement is recommended every 72,000 km (45,000
miles) under normal conditions, with more frequent service in dusty
environments. Drive Belt: The serpentine accessory drive belt should be
inspected for cracking or glazing every 24,000 km (15,000 miles) and replaced as
necessary.
Cylinder Head Bolts: Bolts are initially torqued to 30
Nm (22 lb-ft), then to 90 Nm (66 lb-ft), followed by an additional 90-degree
turn, and finally a second 90-degree turn.
Main Bearing Caps: The four vertical bolts for the main bearing caps are torqued
to 100 Nm (74 lb-ft), while the two cross-bolts are torqued to 25 Nm (18 lb-ft)
plus an additional 53-degree turn.
Connecting Rod Bolts: The initial torque is 20 Nm (15 lb-ft) plus a 90-degree
turn. Intake Manifold: The intake manifold bolts are torqued in a specific
sequence to 8 Nm (71 lb-in) for the lower manifold and 10 Nm (89 lb-in) for the
upper manifold.
Valve Rocker Arm Bolts: The rocker arm bolts are torqued to 30 Nm (22 lb-ft).
Camshaft Retainer Plate: Bolts are torqued to 12 Nm (106 lb-in). Oil Pan Bolts:
The oil pan bolts are torqued to 25 Nm (18 lb-ft) for the main pan bolts and 12
Nm (106 lb-in) for the rear cover bolts.
Chevrolet Silverado 1500: 2007-2013 model years,
serving as the primary flex-fuel V8 option for light-duty trucks.
Chevrolet Suburban / Tahoe: 2007-2014 model years, where the LC9 provided the
balance of power and efficiency required for full-size SUVs.
Chevrolet Avalanche: 2007-2013 model years, utilized in both 2WD and 4WD
configurations.
GMC Sierra 1500: 2007-2013 model years, paired with the Hydra-Matic 4L60E or
6L80E transmissions.
GMC Yukon / Yukon XL: 2007-2014 model years, offering flex-fuel capability
across the premium SUV lineup.
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