Chevrolet L8T Specifications
| Engine Model: Chevrolet L8T |
| Engine Type: 4-cycle 8-cylinder OHV 16-valve liquid-cooled gasoline |
| Total Displacement: 407 cu.in (5.56 L) |
| Rated Engine Power: 401 Hp (299 kW) at 5200 rpm |
| Fuel System Type: Gasoline Direct Injection |
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The Chevrolet L8T is a heavy-duty 6.6-liter V8 gasoline
engine from General Motors' Gen V Small Block family. Introduced in 2020, it was
designed specifically for heavy hauling and towing in the Silverado HD and
Sierra HD lineups.
Unlike its smaller siblings, the L8T prioritizes durability and simplicity,
omitting complex fuel-saving technologies such as cylinder deactivation and auto
start-stop. This engine features a cast iron block with a forged steel
crankshaft and oil-spray piston cooling, making it a robust foundation for both
work truck applications and high-performance aftermarket builds.
Engine Type: 90-degree V8, Gen V Small Block
Displacement: 6.6 L (6,564 cc; 407 cu.in)
Bore x Stroke: 103.25 mm x 98 mm (4.06 in x 3.86 in)
Compression Ratio: 10.8:1
Firing Order: 1-8-7-2-6-5-4-3
Maximum Horsepower: 401 hp (299 kW) @ 5,200 rpm
Maximum Torque: 464 lb-ft (629 Nm) @ 4,000 rpm
Maximum Engine Speed: 5,600 rpm
Recommended Fuel: 87 octane regular gasoline
Fuel System: Direct Injection (DI)
Valvetrain: Overhead Valve (OHV), 2 valves per cylinder, Variable Valve Timing
(VVT)
Camshaft: Billet steel hydraulic roller
Camshaft Duration (@0.050 in): 193° intake / 199° exhaust
Valve Lift: 12.7 mm (0.500 in) intake / 12.5 mm (0.492 in) exhaust
Rocker Arm Ratio: 1.8:1
Engine Control: ECM with 58X reluctor wheel, internal balance
The cylinder block is constructed from cast iron,
featuring a long-skirt design that enhances structural rigidity and minimizes
flex under heavy loads. It utilizes a six-bolt, cross-bolted nodular main
bearing cap configuration, which provides superior support for the rotating
assembly compared to traditional four-bolt designs.
This robust architecture ensures the engine can withstand sustained high
cylinder pressures and is highly resistant to bore distortion, making it an
ideal platform for forced induction applications.
Cylinder heads are manufactured from cast aluminum and
utilize a rectangular port design optimized for direct injection. The combustion
chamber volume measures 59.02 cc.
The valvetrain employs hollow-stem intake valves measuring 54.1 mm (2.130 in) in
diameter to reduce reciprocating mass, while the exhaust valves are constructed
from Inconel, measuring 40.4 mm (1.590 in), to withstand the extreme thermal
loads associated with heavy towing and high-output scenarios.
The fuel system is comprised of a high-pressure direct
injection architecture. This system delivers fuel directly into the combustion
chamber at high pressure, allowing for precise fuel control and enabling the
10.8:1 compression ratio.
The setup contributes to improved thermal efficiency and torque output compared
to port injection systems. The engine is equipped with a high-pressure fuel pump
mounted on the engine, requiring separate fuel injectors and fuel rails if
sourced as a long block assembly.
The lubrication system utilizes a wet sump design with
a 7.6 L (8.0 US qt) capacity. It incorporates oil-spray cooling jets that direct
oil to the underside of the pistons, which is critical for managing temperatures
during sustained high-load operation such as towing. The system is designed for
5W-30 engine oil meeting dexos1 specifications.
The cooling system is designed for high-capacity
thermal management to support the engine's heavy-duty vocation. It features a
water-cooled cast iron block and aluminum heads configuration with a high-flow
water pump.
The specific coolant capacity varies by
chassis, but the system includes an external engine oil cooler and
utilizes a conventional thermostat for regulating operating temperature.
The engine features a coil-on-plug ignition system for
reliable spark delivery. It does not include Active Fuel Management (AFM) or
Dynamic Fuel Management (DFM), eliminating the hydraulic lifters and oil
manifold complexities associated with cylinder deactivation.
The intake manifold is a composite construction
with a single-bore 87 mm throttle body. The engine is equipped with a
forged steel crankshaft, forged powder-metal connecting rods, and
hypereutectic aluminum pistons.
The crate engine package weight is 295 kg (650 lbs)
including the throttle body, intake manifold, exhaust manifolds, and oil pan.
The physical dimensions of the crate package are 1,118 mm (44.0 in) in length,
813 mm (32.0 in) in width, and 948 mm (37.3 in) in height.
Engine Oil Capacity (with filter): 7.6 L (8.0 qt).
Recommended Oil Viscosity: SAE 5W-30.
Oil Specification: dexos1.
Fuel Requirement: 87 octane (R+M)/2.
Spark Plug Gap: Refer to vehicle-specific service manual for OEM specifications.
Engine Idle Speed: 600-700 rpm (High Idle Mode available up to 1,200 rpm).
Camshaft Sprocket (VVT Bolt): 48 ft-lbs (65 Nm) + 90
deg.
Camshaft Retainer Plate Bolts: 11 ft-lbs (15 Nm).
Cylinder Head Bolts: 22 ft-lbs first pass + 90 deg.
Connecting Rod Bolts: 15 ft-lbs + 60 deg.
Crankshaft Balancer Bolt: 240 ft-lbs (325 Nm).
Water Pump Bolts: 18-22 ft-lbs (24-30 Nm).
Accessory Drive Stud: 58 Nm (43 lb-ft).
Accessory Drive Bolts: 22 Nm (16 lb-ft).
Main Cap Side Bolts: 22 ft-lbs (30 Nm) + 60 deg.
Chevrolet Silverado 2500HD: 2020-Present
Chevrolet Silverado 3500HD: 2020-Present
GMC Sierra 2500HD: 2020-Present
GMC Sierra 3500HD: 2020-Present
Chevrolet Express 2500/3500: 2021-Present
GMC Savana 2500/3500: 2021-Present
Chevrolet Low Cab Forward (LCF) 4500HD/4500HG: 2021-Present
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