In addition to revamped exterior styling, a freshened features list and the latest tech, the new 2020 GMC Sierra HD and 2020 Chevrolet Silverado HD will also come equipped with a new gasoline powerplant option: the GM L8T 6.6L V8 gasoline engine. We recently captured it out in the open at the 2019 New York International Auto Show. Mounted on a stand, we can clearly see the engine’s design, as well as a cutaway of the intake manifold and the block.
Earlier this year, we shared with you the L8T’s spec sheet, and all told, the new 6.6L is a major improvement compared to the motor it replaces – 6.0L V8 L96. An evolution of the fifth-gen Small Block architecture first seen on the 6.2L V-8 LT1, the L8T produces 401 horsepower at 5,200 rpm and 464 pound-feet of torque at 4,000 rpm, which is an 11 percent increase in power and a 22 percent increase in torque compared to the L96. For those keeping score at home, the GM L8T lays down an additional 41 horsepower and 84 pound-feet of torque compared to the 360 horsepower and 380 pound-feet of torque produced by the Vortec L96.
Critically, the peak horsepower and peak torque figures on the GM L8T 6.6L V8 arrive 200 rpm sooner than on the L96, which is exactly what you want in a heavy-duty truck application.
Unlike the LT1 and its aluminum block, the L8T features an iron block. Although heavier than aluminum, iron construction also tends to be much more durable and robust. Additional features of the GM L8T engine include:
- Aluminum heads
- A forged steel crankshaft
- Forged connecting rods
- An OverHead Valve (or push-rod) layout
- Two valves per cylinder
- Variable valve timing
The bore-and-stroke ratio of the GM L8T is set at 103.5 mm x 98 mm, as compared to the 103.25 x 92 mm bore-and-stroke ratio of the LT1. The L8T also comes with a lower 10.8:1 compression ratio, as opposed to the 11.5:1 compression ratio on the LT1.
In the 2020 Silverado HD and 2020 Sierra HD, the GM L8T engine will be mated to the GM 6L90 six-speed automatic transmission, with both two-wheel- and four-wheel-drive on hand to put the power to the ground.
All we can say is that we’re glad the all-new Silverado HD and Sierra HD will finally get an all-new, modern gasoline engine that the deserve. After all, the outgoing L96 engine is nearly 20 years old at this point, so it’s about time these workhorses got a proper powerplant under the hood.