GM 6.2L LT4 Engine Specs, Problems, Reliability, Info

6.2 LT4 Supercharged V8 Engine Info

The LT4 is an all-aluminum 6.2-liter supercharged direct-injected V8 gasoline engine produced by General Motors, and it is part of the fifth-generation Small Block engine family. This motor was introduced in the 2014 Corvette C7 Z06, replacing the previous supercharged 6.2-liter Gen IV LS9 engine. Additionally, the LT4 engine was used to power the sixth-generation Camaro ZL1 and various high-performance Cadillac vehicles, including the Cadillac Escalade V, Cadillac CTS-V, and the CT5-V Blackwing. Thanks to its robust design, the LT4 engine is able to generate significant horsepower and torque, providing remarkable dynamic performance for these GM models. Let's look at what's inside this motor and how it produces so much power.

LT4 Engine Overview

The supercharged LT4 is built on the same Gen 5 small block architecture as the naturally aspirated 6.2L LT1, but the LT4 has more reinforced internal components. The base of the engine is a 90-degree V-shaped aluminum cylinder block with cast-in iron liners and 6-bolt main caps. The LT4 engine block is fitted with a forged steel crankshaft, forged powdered metal steel I-beam connecting rods, reinforced forged aluminum pistons with a flat top, and an anodized aluminum harmonic balancer for reduced mass. The compression ratio is 10:1, which is lower than the LT1 ratio of 11.5:1. the oiling system features a dual-pressure-control oil pump (variable-displacement vane pump) and oil squirters that cool and lubricate pistons from the bottom. Also worth noting that the Corvette Z06 LT4 engine came with a dry sump oiling system, while the Camaro ZL1 and Cadillac models had a wet sump.

Instead of conventional aluminum heads, the 6.2L LT4 has Rotocast A356-T6 aluminum cylinder heads for more strength and better heat dissipation. These heads feature two valves per each cylinder, rectangular intake ports, oval exhaust ports, lightweight titanium solid-stem intake valves, and steel sodium-filled exhaust valves. Intake valve diameter is 2.126 inches (54 mm), exhaust valves diameter is 1.590 in (40.4 mm). Intake valve angle is 12.5 degrees, exhaust valve angle — 12.0 degrees. While the LT1 and LT4 have the same valve sizes, their camshafts are different. The LT4 camshaft specs: 188/223 duration (int./exh.), 0.502 in./0.561 in. valve lift (int./exh.). The cam also equipped with a phaser of the variable valve timing (GM's Dual-Equal Cam Phasing technology). The valvetrain features hydraulic lifters, 7.85-inch-long pushrods and roller-pivot rocker arms. It is also worth noting that all versions of the LT4 (except for ZL1 Camaro with manual transmission) came with a cylinder deactivation system called AFM (Active Fuel Management).

All fifth-gen small-block V8s use direct fuel injection, which shoots fuel directly into the combustion chamber rather than the intake ports. This system requires a very high fuel pressure, up to 15 MPa (150 bars). In addition to a conventional tank-located fuel pump, the LT4 has an engine-driven high-pressure fuel pump mounted in a valley between the two cylinder heads. The HP pump feeds a U-shaped fuel rail that maintains pressure at 2,900 psi. This fuel rail is connected to eight direct injectors with a fuel flow of 141 lbs./hr. By the way, LT4 is not flex-fuel capable (E85).

What makes the LT4 unique is the next-generation Eaton supercharger/intercooler. The factory-stock engine uses a 4-lobe, positive displacement, roots-type 1.7 L Eaton R1740 TVS supercharger. While this compact unit is smaller than the previous 2.3-liter LS9 supercharger, it spins at 5,000 RPM faster (up to 20,000 rpm) and is able to generate nearly the same boost pressure (over 9 psi), but quicker. The engine speed is controlled by a 4-bolt 87 mm electronic throttle body (also known as drive-by-wire). The ignition system features 58X crank timing, individual coil-on-plug coils and extended life spark plugs. And lastly, the LT4 got cast stainless-steel exhaust manifolds, which provides more strength at high temperatures than cast-iron manifolds.

What is the result? The standard LT4 engine in the Corvette Z06 delivers up to 650 hp and 650 ft-lb of torque, 195 hp and 195 ft-lb more compared to the NA 6.2L LT1. Such big improvements gave the roadster a top speed over 200 mph and a less than 3 seconds from 0 to 60.

Cadillac Escalade-V Engine

The 2023+ Cadillac Escalade-V is powered by a unique LT4 version, which produces 682 horsepower and 653 lb-ft of torque. A major difference between the LT4 in the 2022+ CT5-V Blackwing and Escalade-V is a 2.65L Eaton R2650 supercharger that spins at 13,500 rpm to generate approximately 10 pounds of boost. Moreover, 80% of its peak torque is reached at 2,000 rpm, which is very useful for a full-size luxury SUV.

Engine Specs

GM 6.2L LT4 Reliability and Longevity

The LT4 engine is designed to last, and it is hand-assembled at GM's Performance Build Center, which raise its quality and reliability. In factory-stock condition, it is generally considered to be a very robust engine, capable of handling high horsepower and high RPMs. However, modified ones require some component upgrades to eliminate potential weak points.

Of course, this motor is not flawless. The first issue is carbon build-up. This is a common problem and a well-known disadvantage of direct injection engines. There is no fuel in the intake ports, helping to wash away burnt oil and dirt from the intake valves and walls. Over time, the engine can accumulate a lot of carbon, leading to significant airflow restriction, which is not good for power, fuel consumption, and so on. This system also puts high fuel requirements. Bad fuel can easily damage a high-pressure fuel pump or clog direct fuel injectors.

The second weak point is an oil pump. A defective oil pump was known to cause huge failures on 2017–2018 models. An engine might work fine with no symptoms, and then suddenly lose oil pressure to zero. This failure usually happens within the first 40k miles range. Moreover, a stock LT4 pump is not durable enough for high-stress applications.

It is also worth mentioning that the LT4 engine is equipped with AFM (a cylinder deactivation technology). This system is known for having reliability issues. The primary problems with AFM are lifter failure, wear on the camshaft, and excessive oil consumption.

The Summary

The factory-stock 6.2-liter LT4 engine is built to serve at least 150,000 miles. Keep in mind, this is a high-performance, supercharged engine that requires frequent oil changes, premium gasoline, high-quality filters, and parts. However, its longevity heavily depends not only on maintenance, but also how it is driven, and any modifications.