The GM LZ8 is a 3,929 cc, naturally aspirated V6 petrol engine produced between 2005 and 2008. It features sequential multi-port fuel injection, a cast-iron block, and overhead valve (OHV) pushrod design. This powerplant delivered 152–155 kW (205–208 PS) and 320–328 Nm of torque, with its torque-focused character engineered for smooth, predictable performance in midsize applications.
Fitted to models such as the Chevrolet Impala, Pontiac Grand Prix, and Buick LaCrosse, the LZ8 was engineered for drivers prioritizing refinement, low-end torque, and everyday reliability over high-RPM power. Emissions compliance was achieved through precise electronic throttle control and advanced catalytic converter placement, allowing compliance with U.S. Tier 2 Bin 5 standards for its production era.
One documented concern is potential for intake manifold gasket failure, which can lead to coolant or vacuum leaks. This issue, addressed in GM Service Bulletin 06-06-01-009B, is attributed to material degradation in the factory-installed gasket. GM issued revised gasket material for affected vehicles.
Production years 2005–2008 meet U.S. EPA Tier 2 Bin 5 standards (EPA Certificate of Conformity #AALMF.LZ840).
The GM LZ8 is a 3,929 cc V6 naturally aspirated petrol engineered for full-size sedans and coupes (2005-2008). It combines sequential multi-port fuel injection with an overhead valve pushrod design to deliver smooth, low-RPM torque and reliable everyday performance. Designed to meet U.S. Tier 2 Bin 5 standards, it balances refinement with regulatory compliance for its era.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,929 cc | |
| Fuel type | Petrol | |
| Configuration | V6, 90°, OHV, 12-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 99.0 mm × 84.5 mm | |
| Power output | 152–155 kW (205–208 PS) | |
| Torque | 320–328 Nm @ 4,000 rpm | |
| Fuel system | Sequential Multi-Port Fuel Injection (SFI) | |
| Emissions standard | U.S. Tier 2 Bin 5 | |
| Compression ratio | 9.9:1 | |
| Cooling system | Water‑cooled | |
| Timing system | Chain‑driven | |
| Oil type | API SM (SAE 5W‑30) | |
| Dry weight | 169 kg |
The OHV pushrod design provides strong low-end torque ideal for highway cruising and towing but requires vigilant monitoring of the intake manifold gasket for signs of failure, as per SIB 06-06-01-009B. The timing chain is generally maintenance-free but should be inspected if noise develops. Regular oil changes with API SM 5W-30 are critical for protecting the hydraulic lifters and camshaft. Coolant should be flushed every 5 years to prevent corrosion in the cast-iron block and aluminum heads.
Oil Specs: Requires API SM specification (GM Owner's Manual). Essential for hydraulic lifter and camshaft longevity.
Emissions: Certified to U.S. EPA Tier 2 Bin 5 standards (EPA Certificate #AALMF.LZ840). Applies to all model years 2005–2008.
Power Ratings: Measured under SAE J1349 standards (GM PT-2005).
GM Technical Service Manuals: J-39254, PT-2005
GM Service Bulletin: 06-06-01-009B
U.S. Environmental Protection Agency: Certificate of Conformity #AALMF.LZ840
SAE International: J1349 Engine Power Certification Standards
The GM LZ8 was used across GM's W-body and Epsilon platforms with transverse mounting. This engine received no major platform-specific adaptations or facelift revisions affecting core interchangeability within its production run. All applications are documented in OEM service manuals.
Locate the engine code 'LZ8' stamped on a machined pad on the front of the engine block, near the timing cover (GM Service Manual J-39254). The 8th digit of the VIN is '8' for this engine. Visually, it can be identified by its 90° V6 layout, cast-iron block, and prominent intake manifold spanning the valley between the cylinder heads. Critical differentiation from the 3.5L LX9: The LZ8 has a larger displacement (3.9L vs 3.5L) and a visibly larger intake manifold. While externally similar, internal components like the crankshaft and connecting rods are specific to the LZ8.
The LZ8's primary documented concern is intake manifold gasket failure, with elevated incidence in high-mileage or frequently heat-cycled engines. GM service data indicates this was a widespread issue leading to coolant and vacuum leaks. Neglecting coolant changes or using incorrect oil can accelerate wear on the hydraulic lifters, making adherence to maintenance schedules critical.
Analysis derived from GM technical bulletins (2005-2008) and NHTSA consumer complaint data (2006-2010). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about GM LZ8.
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