The GM L8T engine is produced by General Motors for use in Heavy Duty pickup trucks. The gasoline powerplant displaces 6.6 liters in a V8 configuration and an OverHead Valve (OHV) layout, otherwise referred to as push-rod.
The L8T is part of GM’s fifth-generation Small Block engine family and made its debut in the all-new 2020 Chevrolet Silverado HD and 2020 GMC Sierra HD.
Overview
The 6.6L V8 L8T engine is built on a cast-iron Small Block, enabling it to have long-term durability. Thanks to aluminum heads and direct injection, it delivers more precise fuel control resulting in a higher compression ratio of 10.8:1. That enables a power output of 401 horsepower and 464 pound-feet of torque (in the 2020 Silverado HD and 2020 Sierra HD), with strong performance at low rpm, where it is needed when pulling away with a loaded cargo box or trailer.
The L8T also features a forged steel crankshaft, forged powder-metal connecting rods and additional high-strength components to provide the added strength and durability demanded by Heavy Duty truck customers.
Notably, the L8T does not use cylinder deactivation technologies like Active Fuel Management (AFM) or Dynamic Fuel Management (DFM). It’s also not equipped with Auto Stop-Start (ASS).
Production of the L8T engine takes place at the GM Tonawanda Plant in Buffalo, New York.
Specifications
| GM RPO Code: | L8T |
|---|---|
| Type: | 6.6L V-8 gasoline |
| Bore & Stroke (in / mm): | 4.06 x 3.86 / 103.25 x 98 |
| Block Material: | Cast iron with nodular iron main caps |
| Cylinder Head Material: | Cast aluminum |
| Intake Manifold Material: | Composite |
| Exhaust Manifold Material: | Stainless steel |
| Main Bearing Caps Material: | Cast nodular iron |
| Crankshaft Material: | Forged steel |
| Camshaft Material: | Billet steel |
| Connecting Rod Material: | Forged powder metal |
| Compression Ratio: | 10.8:1 |
| Valvetrain: | Overhead-valve, two valves per cylinder, variable valve timing |
| Fuel Delivery: | Direct fuel injection |
| Valve Lifters: | Hydraulic roller |
| Firing order: | 1-8-7-2-6-5-4-3 |
| Recommend Fuel: | 87 octane (regular) |
| Orientation: | Longitudinal |
| Power (hp / kW @ rpm): | 401 / 299 @ 5200 (SAE certified) |
| Torque (lb.-ft. / Nm @ rpm): | 464 / 629 @ 4000 (SAE certified) |
| Maximum Engine Speed: | 5,600 RPM |
| Emissions Control: | Catalytic converters, three-way catalyst, positive crankcase ventilation |
| Length (mm / in): | 755.5 / 29.74 |
| Width (mm / in): | 663.7 / 26.1 |
| Height (mm / in): | 795.0 / 31.3 |
| Predecessor: | 6.0L V8 L96/LC8 |
| Successor: | None currently |
| Assembly: | Tonawanda, New York, USA |
Vehicle Applications
| Manufacturer | Model Year | Make | Model | Transmission | Power (hp / kW) @ RPM | Torque (lb-ft / Nm) @ RPM |
|---|---|---|---|---|---|---|
| General Motors Company | 2020-2023 | Chevrolet | Silverado HD | 6-speed auto (6L90) | 401 / 299 @ 5200 | 464 / 629 @ 4000 |
| General Motors Company | 2020-2023 | GMC | Sierra HD | 6-speed auto (6L90) | 401 / 299 @ 5200 | 464 / 629 @ 4000 |
| General Motors Company | 2024-Present | Chevrolet | Silverado HD | 10-speed auto (10L90) | 401 / 299 @ 5200 | 464 / 629 @ 4000 |
| General Motors Company | 2020-Present | GMC | Sierra HD | 6-speed auto (10L90) | 401 / 299 @ 5200 | 464 / 629 @ 4000 |
- All figures SAE certified
Chronology
The L8T replaces the 6.0L V8 L96 / LC8 engine, making over 11 percent more horsepower and over 21 percent more torque than its predecessor.
Currently, no successor to the L8T is in production.
Crate Engine
In December 2022, GM introduced the L8T as a crate engine, where it makes 430 horsepower (at 5,500 RPM) and 475 pound-feet of torque (at 4,000 RPM) and weighing 580 horsepower.
Nickname
The L8T engine is sometimes referred to as “late”, since that’s what the L8T RPO code spells out.
News
Follow our L8T news coverage.
