With an SAE-certified 355 hp (265 kW) and 383 lb-ft (519 N·m) of torque—increases of 40 hp and 48 lb-ft compared to the 2013 model—Sierra’s new 5.3L offers towing capacity of up to 11,500 pounds.

Most GMC owners—three out of four last year—will opt for the 5.3L V-8 engine, which is an $895 option, according to GM.

The 5.3L EcoTec3 V-8 is one of three more efficient new engines for the Sierra; a 4.3L EcoTec3 V-6 is standard. Sierra also will be available later this year with a new 6.2L EcoTec3 V-8 with more power, torque and capability than the 5.3L. Additional specifications for the 6.2L will be released later.

EcoTec3. Announced in December 2012, the new EcoTec3 engines feature three advanced technologies—direct injection, cylinder deactivation and continuously variable valve timing (CVVT)—to make the most of power, torque and efficiency across a broad range of operating conditions. The new engine family includes a 4.3L V6, a 5.3L V-8 and a 6.2L V-8, all matched with six-speed transmissions.

The EcoTec3 engines use direct fuel injection to optimize combustion over a broad range of conditions. The engines also feature a new cylinder-head design and a new, sculpted piston to optimize the mixing of air and fuel in the engine and the burning of the mixture to create power.

The heads features smaller combustion chambers shaped to complement the unique topography of the piston heads. The smaller chamber size and sculpted pistons produce a compression ratio of 11.0:1 or higher, depending on the engine, while the heads features large, rectangular intake ports with a slight twist to enhance mixture motion.

To further enhance combustion, the intake and exhaust valve positions have been switched from previous versions, and the valves are now slightly canted toward the cylinder centerline. Also, the spark plug angle has been revised and the electrode is now closer to the center of the chamber to support optimal combustion.

The pistons feature unique sculpted topography that was optimized via extensive computer analysis to precisely direct the fuel spray for better mixing and more complete combustion. The contours of the piston heads are machined after casting to ensure dimensional accuracy.

Cylinder deactivation, also known as Active Fuel Management (AFM), is now standard on all three engines for the Silverado and Sierra 1500.

The system uses oil pressure, controlled by the powertrain control module, to deactivate the lifters on selected cylinders, closing the valves for those cylinders. It deactivates four of the cylinders on the V-8 engines and two cylinders on the V-6 under light load conditions—operating the engines as a V-4—and seamlessly reactivates the cylinders when the driver demands greater power. The transition takes less than 20 milliseconds and is virtually imperceptible.