Race-proven legacy, state-of-the-art performance
The first Small Block V-8 debuted in the Corvette in 1955. It displaced 4.3L (265 cubic inches) and was rated at 195 horsepower, drawing air and fuel through a four-barrel carburetor. Five years later, V-8 power helped Corvette secure its first victory at the 24 Hours of Le Mans.
In 2012, the Small Block-powered Corvette Racing C6.R beat Ferrari, BMW and Porsche to sweep the drivers', team, and manufacturer championships in production-based American Le Mans Series GT class. These championships make Corvette Racing the most successful team in ALMS history, with a total of 77 class wins, eight drivers' championships, and nine manufacturer and team championships since 2001.
“The engine requirements for a production car and a racecar are remarkably similar,” said Jordan Lee, Small Block chief engineer and program manager. “In both cases, you want an engine that is powerful and efficient, compact and lightweight, and durable. That combination is what made the original Small Block so successful. Today, the introduction of state-of-the-art technologies and engineering makes one of the best performance car engines in the world even better.”
As an example, the new LT1 engine is 40lbs lighter than a competitor's twin-turbo 4.4L, DOHC V-8 with similar output. That weight savings not only improves the Corvette's power-to-weight ratio, but also contributes to a near-perfect 50/50 weight balance for enhanced steering response and handling.
The new LT1 is also four inches shorter in overall height than the competitive DOHC V-8. That also improves handling by lowering the center of gravity while enabling a low hood line – contributing to the Corvette's iconic profile, as well as ensuring exceptional driver visibility.
The new LT1 is the third engine in the Corvette's history to be so-named, with previous versions introduced in 1970 (Gen 1) and 1992 (Gen 2). All iterations of the LT1 – and all Small Block engines – have shared a compact design philosophy that fosters greater packaging flexibility in sleek vehicles such as the Corvette.
“The power and efficiency of the Small Block V-8 are hallmarks of Corvette performance,” said Lee. “But, the compact size and great power-to-weight are just as important for the overall driving experience. The all-new LT1 will play a huge role in making the all-new Corvette a world-class sports car, in terms of technology, performance, and refinement.”
Engine features and highlights
All-aluminum block and oil pan: The Gen 5 block was developed with math-based tools and data acquired in GM's racing programs, providing a light, rigid foundation for an impressively smooth engine. Its deep-skirt design helps maximize strength and minimize vibration. As with the Gen 3 and Gen 4 Small Blocks, the bulkheads accommodate six-bolt, cross-bolted main-bearing caps that limit crank flex and stiffen the engine's structure. A structural aluminum oil pan further stiffens the powertrain.
The block features nodular iron main bearing caps, which represent a significant upgrade over more conventional powdered metal bearing caps. They are stronger and can better absorb vibrations and other harmonics to help produce smoother, quieter performance.
Compared to the Gen 4 engine, the Gen 5's cylinder block casting is all-new, but based on the same basic architecture. It was refined and modified to accommodate the mounting of the engine-driven direct injection high-pressure fuel pump. It also incorporates new engine mount attachments, new knock sensor locations, improved sealing and oil-spray piston cooling.
Advanced oiling system, with available dry-sump system: The LT1 oiling system – including oil-spray piston cooling – was also optimized for improved performance. It is driven by a new, variable-displacement oil pump that enables more efficient oil delivery, per the engine's operating conditions. Its dual-pressure control enables operation at a very efficient oil pressure at lower rpm coordinated with AFM and delivers higher pressure at higher engine speeds to provide a more robust lube system for aggressive engine operation.
Standard oil-spray piston cooling sprays the underside of each piston and the surrounding cylinder wall with an extra layer of cooling oil, via small jets located at the bottom of the cylinders. For optimal efficiency, the oil jets are used only when they are needed the most: at start-up, giving the cylinders extra lubrication that reduces noise, and at higher engine speeds, when the engine load demands, for extra cooling and greater durability.
An available dry-sump oiling system promotes exceptional lubrication system performance during aggressive driving maneuvers and high cornering loads. It includes two stages: a pressure stage and a scavenge stage. The pressure stage includes the new, dual-pressure-control and variable-displacement vane pump.
Dexos semi-synthetic motor oil, with a 5W30 specification, helps reduce friction to further enhance the LT1's efficiency.
New, tri-lobe camshaft: Compared to the Gen 4 Small Block, the camshaft remains in the same position relative to the crankshaft and is used with a new rear cam bearing, but it features an all-new “tri-lobe” designed lobe which exclusively drives the engine-mounted direct injection high-pressure fuel pump, which powers the direct-injection combustion system. The cam's specifications include 14mm/13.3mm (0.551/0.524-inch) intake/exhaust lift, 200/207-crank angle degrees intake/exhaust duration at 0.050-inch tappet lift and a 116.5-degree cam angle lobe separation.
New, cam-driven fuel pump: The direct injection system features a very-high-pressure fuel pump, which delivers up to 15Mpa (150 bar). The high-pressure, engine-driven fuel pump is fed by a conventional fuel-tank-mounted pump. The direct injection pump is mounted in the “valley” between cylinder heads – beneath the intake manifold – and is driven by the camshaft at the rear of the engine. This location ensures any noise generated by the pump is muffled by the intake manifold and other insulation in the valley.
PCV-integrated rocker covers: One of the most distinctive features of the new engine is its domed rocker covers, which house the, patent-pending, integrated positive crankcase ventilation (PCV) system that enhances oil economy and oil life, while reducing oil consumption and contributing to low emissions. The rocker covers also hold the direct-mount ignition coils for the coil-near-plug ignition system. Between the individual coil packs, the domed sections of the covers contain baffles that separate oil and air from the crankcase gases – about three times the oil/air separation capability of previous engines.
Intake manifold and throttle body assembly: The LT1's intake manifold features a “runners in a box” design, wherein individual runners inside the manifold feed a plenum box that allows for excellent, high-efficiency airflow packaged beneath the car's low hood line.
Acoustic foam is sandwiched between the outside top of the intake manifold and an additional acoustic shell to reduce radiated engine noise, as well as fuel pump noise.
The manifold is paired with an electronically controlled throttle, featuring an 87mm bore diameter and a “contactless” throttle position sensor design that is more durable and enables greater control.
Four-into-one exhaust manifolds: The LT-1 uses a cast version of the “four-into-one” short-header exhaust manifold design used on the Gen 4 LS7 engine. The cast header passages enable consistent exhaust flow into the “wide mouth” collector at the converter.
Cooling system, humidity sensor and more: Additional features and technologies of the Gen 5 Small Block include:
- A revised cooling system with an offset water pump and thermostat for more efficient performance
- Air induction humidity sensor ensures optimal combustion efficiency, regardless of the surrounding air's humidity
- 58X ignition system with individual ignition coil modules and iridium-tip spark plugs
- All-new “E92” engine controller.