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Chevrolet LQ9 Specifications
| Engine Model: Chevrolet LQ9 |
| Engine Type: 4-cycle 8-cylinder OHV 16-valve liquid-cooled gasoline |
| Total Displacement: 364.1 cu.in (5.96 L) |
| Rated Engine Power: 350 Hp (261 kW) at 5200 rpm |
| Fuel System Type: Sequential port fuel injection (SFI) |
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| General Technical Data |
The Chevrolet LQ9 is a 6.0-liter, V8, naturally
aspirated gasoline engine. It is a high-output variant of General Motors
Generation III Small Block V8 family, specifically within the Vortec
truck engine lineup. Produced from 2002 through 2007, this engine was
engineered for longitudinal installation in high-performance full-size
trucks and sport utility vehicles. The LQ9 is distinguished by its
high-compression, flat-top piston design and specific cylinder heads,
earning it the "Vortec HO" designation.
It maintains a traditional pushrod (OHV) valvetrain with two valves per
cylinder, but benefits from premium internal components. A sequential
fuel injection (SFI) system manages fuel delivery. The engine's design
objective was to deliver increased Hp and torque over standard truck
V8s, providing superior towing capability and acceleration for
performance-oriented truck applications.
Engine Type: 90-degree V8, gasoline, overhead valve (OHV/pushrod)
Displacement: 5967 cc (364.1 cubic inches)
Bore: 101.6 mm (4.000 inches)
Stroke: 92.0 mm (3.622 inches)
Compression Ratio: 10.0:1
Firing Order: 1-8-7-2-6-5-4-3
Cylinder Numbering: Left bank (driver side): 1-3-5-7; Right bank
(passenger side): 2-4-6-8
Maximum Power Output: 261 kW (350 Hp) at 5200 rpm
Maximum Torque: 515 Nm (380 lb-ft) at 4000 rpm
Fuel Type: Unleaded gasoline, 87 AKI (91 RON) minimum (premium
recommended for optimal performance)
Oil Quality Specification: API SL or newer, GM Standard GM6094M
Engine Oil Capacity (including filter): 5.7 liters (6.0 US quarts)
Coolant Capacity (total system): 13.2 liters (13.95 US quarts)
| Cylinder Block |
The LQ9 uses a cast iron cylinder block with a high nickel content (identified by "C" castings), providing enhanced strength and durability. This block incorporates a six-bolt main bearing cap configuration - four vertical bolts and two cross-bolts per main cap - ensuring maximum crankshaft stability under high load. The crankshaft is a nodular iron casting with induction-hardened journals.
Cylinder bores are machined directly into the iron block. Connecting rods are powdered metal units with fractured-cap big ends. A key distinguishing feature is the use of flat-top pistons, constructed from hypereutectic aluminum alloy. These pistons, combined with smaller combustion chambers, achieve the higher 10.0:1 compression ratio. They are fitted with low-tension rings for reduced friction. The camshaft is situated in the block's valley.
| Cylinder Head and Valves |
The LQ9 is equipped with aluminum alloy cylinder heads, cast under the GM "317" casting number. These heads feature cathedral-shaped intake ports but are distinguished by smaller, 68.3 cubic centimeter (4.17 cubic inch) combustion chambers (compared to the 71.2 cc chambers on the LQ4). Each cylinder operates with a single 2.00-inch (50.8 mm) intake valve and a single 1.55-inch (39.4 mm) exhaust valve, both manufactured from steel.
Valve actuation is via hydraulic roller lifters, pushrods, and stamped steel rocker arms with a 1.7:1 ratio. Dual valve springs with damper coils are used to handle higher engine speeds. The cylinder head gaskets are multilayered steel (MLS) to seal the higher combustion pressures. The heads are secured with six bolts per cylinder.
| Fuel System |
Fuel delivery is managed by a sequential port fuel injection (SFI) system. This system is a returnless design, utilizing an electric in-tank fuel pump. A fuel rail assembly supplies eight individual injectors, one for each cylinder. Fuel pressure is regulated at the fuel tank module. The system is controlled by a 32-bit PCM (Powertrain Control Module).
The PCM processes data from a comprehensive sensor array, including a mass air flow (MAF) sensor, throttle position sensor (TPS), manifold absolute pressure (MAP) sensor, dual heated oxygen sensors, and knock sensors. The throttle body is electronically controlled (drive-by-wire).
| Lubrication System |
Lubrication is provided by a high-volume gerotor-style oil pump, mounted to the front of the block and driven directly by the crankshaft. The system is designed for high-pressure operation. Oil is drawn from a baffled, deep-sump oil pan, pressurized, and forced through a full-flow spin-on oil filter.
Filtered oil is directed into the main oil gallery, supplying the crankshaft main and connecting rod bearings, camshaft bearings, and hydraulic lifters. Oil travels through hollow pushrods to lubricate the rocker arms and valve stems. A pressure relief valve within the pump housing maintains system pressure. The system is engineered to maintain adequate oil pressure under high-load and high-rpm conditions.
| Cooling System |
Coolant circulation is handled by a heavy-duty, belt-driven water pump. The system is regulated by a 195°F (91°C) wax-type thermostat, housed in a thermostat housing at the front of the intake manifold. Coolant flows from the pump through the block, upward into the cylinder heads, and then to a large aluminum cross-flow radiator.
A mechanical engine cooling fan, mounted to a viscous clutch drive, provides airflow. The fan clutch engagement is controlled by a bi-metallic coil sensitive to under-hood air temperature. A pressurized coolant recovery reservoir serves as the fill point and expansion tank. The cooling system is designed to manage the additional heat generated by the higher compression ratio and output.
| Intake and Exhaust Systems |
The intake manifold is a composite plastic design for weight reduction and thermal insulation. The exhaust manifolds are cast iron. The exhaust system is a dual-bank setup, merging into a single pipe after the catalytic converters.
The system includes close-coupled pre-catalytic converters on each bank and a main underbody catalytic converter. An Exhaust Gas Recirculation (EGR) system is employed for emissions control. The LQ9 was often paired with a larger, more aggressive exhaust system from the factory compared to lower-output variants.
| Ignition System |
The engine uses a coil-near-plug, distributorless ignition system. Eight individual ignition coils, mounted directly on the valve covers, fire each spark plug via short boots. The PCM controls ignition timing for each cylinder independently based on inputs from crankshaft position (CKP) and camshaft position (CMP) sensors. The system uses platinum-tipped spark plugs with a long service interval. Knock sensors allow the PCM to retard timing if detonation is detected, protecting the high-compression engine.
| Engine Control and Electronics |
Engine management is fully integrated into the vehicle's Powertrain Control Module (PCM). This unit controls all aspects of fuel, ignition, and emissions systems. The PCM communicates via a Class 2 serial data bus. The engine features electronic throttle control (ETC). A dedicated knock sensor module processes signals from the block-mounted sensors to inform ignition timing adjustments.
| Dimensions and Weight |
Length (from bellhousing to water pump pulley): 780 mm (30.71 inches)
Width (across exhaust manifolds): 760 mm (29.92 inches)
Height (from oil pan to intake manifold): 740 mm (29.13 inches)
Dry Weight (without accessories): 223 kg (492 lbs)
| Maintenance Data |
Recommended Service Intervals:
Engine Oil and Filter Change: 8000-12000 km (5000-7500 miles) or 6-12
months, depending on service conditions.
Air Filter Element Replacement: 48000 km (30000 miles) or as required.
Spark Plug Replacement: 160000 km (100000 miles).
Coolant Replacement: 240000 km (150000 miles) or 5 years with Dex-Cool
coolant.
Serpentine Drive Belt Inspection: Check at oil change; replace per
condition.
Fuel Filter Replacement: Recommended at 48000 kilometer (30000 mile)
intervals.
Fluid Specifications and Capacities:
Engine Oil: SAE 5W-30, meeting GM Standard GM6094M (API SL or newer).
Cooling Fluid: Dex-Cool or equivalent OAT (Organic Acid Technology)
coolant.
Automatic Transmission Fluid: Dexron III or VI as specified for the
application.
| Tightening Torques |
Cylinder Head Bolts: Torque-to-yield, single-use bolts. Tighten in three
stages using the proper sequence.
Step 1: 30 Nm (22 lb-ft)
Step 2: Tighten an additional 90 deg of rotation
Step 3: Tighten an additional 90 deg of rotation
Main Bearing Cap Bolts (vertical): 50 Nm (37 lb-ft) plus an additional
77 deg
Main Bearing Cap Cross-Bolts: 20 Nm (15 lb-ft) plus an additional 50 deg
Connecting Rod Cap Bolts: 25 Nm (18 lb-ft) plus an additional 85 deg
(lubricate threads)
Spark Plugs: 15 Nm (11 lb-ft)
Oil Pan Bolts: 25 Nm (18 lb-ft)
Oil Filter: Tighten by hand three-quarters turn after gasket contact
Crankshaft Balancer Bolt: 110 Nm (81 lb-ft) plus an additional 140 deg
Intake Manifold Bolts: 10 Nm (89 pound-inches) for perimeter bolts; 25
Nm (18 lb-ft) for center bolts.
| Vehicle Applications |
The Chevrolet LQ9 Vortec HO engine was
installed in the following vehicles (2002-2007 model years):
Cadillac Escalade EXT
Cadillac Escalade ESV
Chevrolet Silverado SS
GMC Sierra Denali
Chevrolet TrailBlazer SS (specific model years)
Certain high-performance and special edition variants of the Chevrolet
Silverado and GMC Sierra 1500 series.
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