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The Gen V LT1 Small-Block

GM's New Ultimate Weapon

By Barry Kluczyk, Photography by General Motors

Cylinder Deactivation and Variable Valve Timing
Along with direct injection, the Corvette employs active fuel management (AFM) for the first time. That's GM's term for cylinder deactivation technology, which shuts down half of the cylinders in light-load driving to save fuel. Yes, that technically means a C7 may cruise down the freeway as a four-cylinder, but the inherent torque of the big-displacement, 6.2L engine and seamless switching between V4 and V8 modes makes the phenomenon essentially imperceptible.

As for the continuously variable valve-timing system, a vane-type phaser on the front of the camshaft changes its angular orientation relative to the sprocket, thereby adjusting the timing of valve operation on the fly. It is a dual-equal, cam-phasing system that adjusts camshaft timing at the same rate for both intake and exhaust valves. The system allows linear delivery of torque, with near-peak levels over a broad rpm range, and high-specific output (horsepower per liter of displacement) without sacrificing overall engine response or driveability. At idle, for example, the cam is at the full advanced position, allowing exceptionally smooth idling. Under other conditions, the phaser adjusts to deliver optimal valve timing for performance, driveability, and fuel economy. Under a light load, it can retard timing at all engine speeds to improve fuel economy.

New Block Casting, Oiling System, and More
The Gen V's cylinder-block casting is all new but based on the same basic architecture as the previous LS engines. It was refined and modified to accommodate the mounting of an engine-driven, direct-injection, high-pressure fuel pump. It also incorporates new engine-mount attachments, new knock-sensor locations, improved sealing, and provisions for oil-spray piston cooling.

The LT1's oiling system—including oil-spray piston cooling—is 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 active fuel management and delivers higher pressure at higher engine speeds to provide a more robust lube system for aggressive engine operation. A dry-sump oiling system will be available.

Another distinctive LT1 feature is domed rocker covers, which house a unique, integrated positive-crankcase-ventilation (PCV) system that enhances oil economy and oil life while reducing oil consumption and contributing to lower emissions. The rocker covers also hold the direct-mount ignition coils. 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 the LS3.

Additional engine features include a "four-in-one" short-header exhaust manifold design that is very similar to the efficient, low-restriction LS7 design and a revised cooling system with an offset water pump that enhances efficiency.

58 Years of Heritage and No Excuses
In the sports-car world, much will be made about the decision to retain a cam-in-block/overhead-valve configuration for the Corvette's engine when the rest of the competition has long been running dual-overhead cams. The inherent torque of the pushrod design, along with the less complex and more compact packaging for the small-block are important considerations, too. The low-slung hoodline of the Corvette wouldn't be possible if LS engine sported mile-wide and tall DOHC hardware.

High-performance tuning implications notwithstanding, what we've seen of the new LT1 engine demonstrates the General has nothing to apologize for, and the best tag line for the next Corvette might simply be, "Bring it." Hell, the C6.R racing team decimated the competition in its production-based class in the American LeMans Series in 2012, winning the points championship by driving its low-tech pushrod engines past the high-tech hardware of Ferrari, Aston Martin, and others.

We can't wait to experience the new LT1 in the C7 Corvette—and we're even more interested in what tuners will be able to do with it on the second day. Stay tuned.

2014 Corvette LT1 6.2L V8 Specifications
Engine type 90-degree V8 with overhead valves; continuous VVT
Displacement 6.2L (376 ci)
Bore x stroke (in/mm) 4.06x3.62/103.25x92
Cylinder block Cast aluminum with nodular main caps
Main bearing fasteners Six, including two cross bolts per cap
Crankshaft Forged steel
Connecting rods Powder metal, 6.125 inches long
Pistons Eutectic aluminum alloy
Compression ratio 11.5:1
Cylinder heads 319-T7 cast aluminum with 59.02cc combustion chambers
Valve angles (degrees) 12.5 intake, 12 exhaust
Intake valves 2.13 inches (54mm) hollow
Exhaust valves 1.59 inches (40.4mm) hollow sodium
Camshaft Hydraulic-type with tri-lobe for fuel-pump drive
Camshaft lift 0.551-inch (14mm) intake / 0.524-inch (13.3mm) exhaust
Camshaft duration 200-degrees intake/207-degrees exhaust (at 0.050-inch)
Lobe separation angle 116.5 degrees
Fuel delivery Direct injection
Intake manifold "Runners-in-a-box" design; composite construction
Throttle 87mm electronically controlled throttle-body
Ignition 58X with individual coil-on-plug and iridium-tip spark plugs
Horsepower/kW 450/335 (estimated)
Torque: lb-ft/Nm 450/610 (estimated)
Max. engine speed 6,600 rpm (fuel cutoff)

By Barry Kluczyk
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