The GM L3B engine is a turbocharged four-cylinder gasoline engine designed by General Motors. It is an undersquare aluminum DOHC inline-four displacing 2.7 liters (165 cid) and tuned for strong low-end torque.

This article relies largely or entirely on a single source. (August 2022)

In addition to GM's active fuel management, start-stop system, and variable valve timing, which are already featured on GM's other full-size pickup truck engines, this engine also features GM's Intake Valve Lift Control which has 3 different intake cam profiles that are electromagnetically actuated to provide the best fuel economy and performance at a wider range of operating conditions.^[1]

The BorgWarner developed turbo can produce up to 27 psi (1.9 bar) of boost thanks in part to its unique dual volute turbine housing and an electrically actuated wastegate. Instead of two side-by-side exhaust passages like on a regular twin-scroll turbocharger, in this design the two exhaust passages are concentric and allow for better use of the exhaust pulse energy.^[1]

The L3B was first used in the Chevrolet Silverado and GMC Sierra, with an output of 310 hp (231 kW) at 5600 RPM and 348 lb⋅ft (472 N⋅m) at 1500 RPM. With the unveiling of the 2022 model year Silverado, GM announced a significant revision that stiffened and strengthened the engine allowing for a GM-estimated increased maximum torque rating of 430 lb⋅ft (583 N⋅m) while also improving noise, vibration, and harshness (NVH).^[1] Parts are cast at Bedford Casting Operations in Indiana.^[2] Assembly is at Spring Hill Manufacturing, Tennessee, USA.^[3] The L3B is the successor to the 3.6L V6 LGX, 3.6L V6 LGZ, and 4.3L V6 LV3 engines.^[3]

The engine is the first GM truck engine to feature an active thermal management system. This system consists of an electrically driven water pump and a 3-way rotary valve which allows the engine to maintain proper operating temperatures and quicker warm-ups. Also, a continuously variable oil pump helps to lower parasitic losses as well as providing proper lubrication and cooling to the engine, especially under high-load conditions.^[1] The Active Fuel Management system can shutdown the middle two cylinders under low-power conditions.^[2]

Cylinder liners are spun nodular iron.^[2]

The low-output work truck variant runs 10 psi of boost, the 390 lb⋅ft variant runs 20 psi, and the 430 lb⋅ft variant runs 27 psi.^[2]