The Chevrolet LY9 is a 5,967 cc, V8 gasoline engine produced between 2007 and 2011. It features overhead valve (OHV) architecture with two valves per cylinder, sequential multi-port fuel injection, and an aluminum block and heads. In standard configuration, it delivers 315 hp (235 kW) and 338 lb-ft (458 Nm) of torque, providing strong low-end pulling power ideal for full-size trucks and SUVs.
Fitted to models such as the Chevrolet Tahoe, Chevrolet Suburban, and GMC Yukon, the LY9 was engineered for durability in heavy-duty applications. Emissions compliance was achieved through exhaust gas recirculation (EGR), catalytic converters, and closed-loop fuel control, allowing the engine to meet EPA Tier 2 Bin 5 and California LEV II ULEV-200 standards across its production run.
One documented concern is intake manifold gasket leakage observed in 2008–2009 production units, highlighted in General Motors Service Information Bulletin 09145. The issue arises from degradation of the molded rubber gasket due to prolonged thermal cycling, leading to vacuum leaks and rough idle. GM issued an updated multi-layer steel (MLS) gasket in 2010 to resolve the condition.
Chevrolet
Production years 2007–2009 meet EPA Tier 2 Bin 5; 2010–2011 models comply with updated evaporative emissions requirements (EPA-HQ-OAR-2009-0695).
The Chevrolet LY9 is a 5,967 cc V8 gasoline engine engineered for full-size truck and SUV platforms (2007–2011). It combines OHV pushrod design with sequential fuel injection to deliver robust low-end torque and long-term durability. Designed to meet EPA Tier 2 Bin 5 and California LEV II standards, it balances heavy-duty performance with emissions compliance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 5,967 cc | |
| Fuel type | Gasoline | |
| Configuration | V8, OHV, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 101.6 mm × 92.0 mm | |
| Power output | 235 kW (315 PS) @ 5,400 rpm | |
| Torque | 458 Nm @ 4,400 rpm | |
| Fuel system | Sequential multi-port fuel injection | |
| Emissions standard | EPA Tier 2 Bin 5, LEV II ULEV-200 | |
| Compression ratio | 9.9:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Double roller chain | |
| Oil type | GM 4718M 10W-30 or 5W-30 | |
| Dry weight | 210 kg |
The LY9's OHV design provides strong low-RPM torque ideal for towing and hauling, but requires adherence to 10,000-mile oil change intervals to prevent lifter wear and timing chain degradation. GM 4718M 10W-30 or 5W-30 oil is recommended due to its shear stability and compatibility with the hydraulic lifter system. The sequential fuel injection demands TOP TIER detergent gasoline to prevent injector clogging. Post-2010 models feature updated MLS intake manifold gaskets; pre-2010 units should be inspected per GM SIB 09145. Catalytic converters require monitoring to avoid thermal degradation from prolonged rich mixtures or misfires.
Oil Specs: Requires GM 4718M specification (GM SIB 09145). Supersedes earlier GM oil standards.
Emissions: EPA Tier 2 Bin 5 applies to all 2007–2011 models (EPA File EPA-2007-CHEV-007). California models meet LEV II ULEV-200 standards.
Power Ratings: Measured under SAE J1349. Output assumes 87 octane fuel (GM TIS Doc. 30784).
General Motors Technical Information System (TIS): Docs 30784, 31007, SIB 09145
EPA Certification Database (EPA-2007-CHEV-007)
SAE International: J1349 Engine Power Certification Standards
The Chevrolet LY9 was used across Chevrolet's GMT900 platform with longitudinal mounting and shared architecture with GMC variants. This engine received platform-specific adaptations-reinforced cylinder heads in the Suburban and revised intake tuning in the Tahoe-and from 2010 the facelifted Tahoe models adopted the LY9 with updated intake gaskets and ECU calibration, creating interchange limits. Partnerships allowed GMC's Yukon to use the LY9 with minor calibration differences. All adaptations are documented in OEM technical bulletins.
Locate the engine ID tag on the passenger side cylinder head near the exhaust manifold (GM TIS 30784). The 8th VIN digit indicates engine type ('L' for LY9 series). Pre-2010 models have silver valve covers with black coil packs; post-2010 units use black valve covers with chrome accents. Critical differentiation from LQ9: LY9 has a 9.9:1 compression ratio and aluminum block, while LQ9 is a high-output version with 10.1:1 compression and cast-iron block. Service parts require model year verification - intake manifold gaskets for 2008–2009 models are incompatible with 2010+ due to material redesign (GM SIB 09145).
The LY9's primary reliability risk is intake manifold gasket leakage in early production models, with elevated incidence in high-temperature and stop-start applications. Internal GM quality reports from 2010 indicated approximately 6% of 2008–2009 units required gasket replacement before 120,000 miles, while NHTSA field reports confirm related rough idle and SES light entries. Frequent thermal cycling and urban driving accelerate gasket fatigue, making timely inspection and preventive replacement critical.
Analysis derived from General Motors technical bulletins (2007-2011) and NHTSA failure statistics (2008-2015). Repair procedures should follow manufacturer guidelines.
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