Getting To Know The LT1 - Part 1

We take a look inside the C7’s all-new engine, with help from the people who know it best

Christopher R. Phillip Apr 12, 2013 0 Comment(s)
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Now that the '14 Corvette has officially been released, fans of the marque are getting their first close-up look at the newest iteration of Chevrolet's classic small-block. Dubbed the LT1, this fifth-generation (Gen V) powerplant has been the subject of more research-and-development manpower than any other V-8 in Chevy history.

"Computational analysis on the Gen V small-block began in 2007, and consumed thousands of terabytes of disk space on General Motors' computers." Assistant Chief Engineer Small Blocks John Rydzewski says.

"Over 10 million hours were dedicated to the computer-aided design of the new LT1, with a whopping 6 million of those hours devoted to its new combustion system. Thirty analysts worked…for three years before the first physical test engine was built. On computers, they evaluated every component in the engine, from the connecting rods to the rocker covers.

"Inside the engine, the shapes and configurations of the rotating parts were evaluated for mass optimization, ensuring the highest quality and durability were achieved with the lightest, most efficient parts. Once the Gen V's basic design was refined on our computers, our engineers constructed prototype engines and tested them on a variety of dynamometers. [These included] a unique tilt-stand fixture that tilted the engine to simulate the load experienced in the Corvette during high-speed cornering on the world's toughest racetracks. It can tilt up to 53 degrees and simulate lateral acceleration of up to 1.3 g's."

Testing on Gen V "mule" engines commenced in late 2010. "[The Gen V] was subjected to the toughest durability testing ever for a V-8 engine from General Motors," Rydzewski says.

How tough?

"GM's engineers designed a grueling performance-durability procedure, where the engine was subjected to a high-speed/high-load torture session that simulated full-throttle blasts from the equivalent of 0 to 120 mph," he says. "With simulated transmission shift points inserted during the test, the engine cycled nonstop between peak torque and peak horsepower for hundreds of hours."

On October 23, 2012, Chevrolet treated VETTE and other media outlets to a sneak peak at the new LT1. Here's what Rydzewski told us after the preview: "The new LT1 is one of the most advanced engines in the industry. These advancements are made possible in part through Design Responsible Engineers and supporting teams, who put in long hours to make sure their parts are proven and provide a great payoff for the customer. All the parts in the LT1 come together to work in harmony as a complete engine delivering at least 450 horsepower, a 0-60 time of less than four seconds, and 26-plus mpg [on the] highway. Every component serves an important purpose and has an interesting story for the Vette enthusiast."

Come along with us now, as we examine the LT1 short block and its internals, and hear GM's Design Responsible Engineers reveal previously top-secret information about the engine. In Part 2, we'll take a look at the engine's impressive new heads and combustion chambers, its direct-injection fueling, its continuous variable valve timing, and much, much more.

Engine Block and Main Caps
Produced at GM's Tonawanda, New York, manufacturing facility, the new LT1 block retains the 4.4-inch bore spacing that has defined every Chevy small-block since 1955. Precision cast from 319 T-7 aluminum, it features 4.06-inch bores, cast-in-place liners, induction liner heating (for dimensional control), an all-aluminum deck face (cast over the liners), SIDI (Spark Ignition Direct Injection) fuel-pump mounting in the valley, revised water jackets, a windage-optimized crankcase, and new engine-mount bosses and rear-cover-mounting provisions. Twenty-five CNC machines at Tonawanda perform more than 400 machining processes on the new block, including boring. There are four main bolts and two cross-bolts per cap.

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Design Responsible Engineer: Dan Baker/LT1 Block
His insider's perspective: "The main caps for the LT1 are made out of nodular iron, which offers improved strength, durability, and stiffness. It also contributes to even more consistent main-bearing clearance as compared with the LS3's powdered-metal main caps, which already had outstanding properties."

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Oil Jets
| In the LT1 block, eight oil-spraying jets drench the underside of each piston and its surrounding cylinder wall with an extra layer of friction-reducing, noise-dampening oil. The oil spray also reduces piston temperature, enabling extreme power output and promoting long-term durability. For optimal efficiency, the oil jets are used only when they're needed the most: at start-up, when they give the cylinders extra lubrication to enhance engine durability, and at higher engine speeds, when the engine load demands it.

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Design Responsible Engineer: Jodie Velzy/LT1 Lube and Vent System
Her insider's perspective: "The LT1's piston squirters, which the oil jets are also known as, also dampen noise, which results in a quieter driving experience. GM has a lot of experience using these in our supercharged LS9 V-8 and some of our four-cylinder engines."

Crankshaft and Main Bearings
Forged from 1538MV steel, this new crankshaft features a 3.62-inch stroke, induction-hardened journals, and intermediate pin drills. The LT1's main rod bearings are polymer coated for increased fatigue strength and robustness over the already durable and proven Gen IV aluminum bimetal bearings.

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Design Responsible Engineer: Paul Gelazin/ LT1 Rotating Cranktrain
His insider's perspective: "The LT1 crank is based on the high-performance LSA/Camaro ZL1 engine-crankshaft design for improved strength and durability."

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Connecting Rod and Rod Bearings
Constructed from forged, high-strength powdered metal, the LT1 rods carry over the 6.125-inch length of their Gen IV predecessors. They use the best design elements of the 6.2L LSA rod utilized in the Camaro ZL1, including a wider rod design, tapered pin, and higher-strength bushing. Like the LT1's main bearings, they're also polymer coated.

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Design Responsible Engineer: Tom Halka/LT1 Piston, Ring, and Rod System
His insider's perspective: "The LT1 connecting rod's lightening features reduce overall mass by 7 grams each compared with the already lightweight LS3 rods."

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Piston-Head Assembly
The LT1 piston head is a first-for-Chevy design, thanks in part to its "pop up" top, direct-injection fuel bowl, and risers to direct the fuel spray for more-complete combustion. Other features include a high-strength body, a valve relief for cam phasing, a skirt notch for the piston-cooling oil jet, an LS3-style ring pack, and cast-and-drilled oil drains. As with the Gen IV unit, it is constructed from eutectic aluminum alloy. The configuration of the piston head is crucial in supporting direct-injection combustion. Smaller combustion chambers (which we'll show you in Part 2) complement the dish volume of the pistons' heads.

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Design Responsible Engineer: Tom Halka/LT1 Piston, Ring, and Rod System
His insider's perspective: "Piston-crown design is an important feature that plays a big part of the significantly improved combustion system. The complete design of the piston system is central to the performance of the LT1's combustion system; high, 11.5:1 compression ratio; and high power output."

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Wet-Sump Oil Pump
This new pump features dual-pressure capability, which produces efficient pressure at low rpm and higher pressure at high rpm for aggressive engine operation.

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Design Responsible Engineer: Jodie Velzy/LT1 Lube and Vent System
Her insider's perspective: "The LT1 wet-sump oil pump can vary real-time output by monitoring main-bearing oil pressure to deliver adequate lubrication to the engine at the maximum efficiency."

Wet-Sump Oil Pan and Windage Tray
The LT1's cast-metal, six-quart oil pan and redesigned windage-tray system are the result of thousands of hours of computational analysis and grueling torture tests on GM's in-house test jig. The pan features a new oil-scraper design, which enhances performance and efficiency by improving oil-flow control and bay-to-bay crankcase breathing. The windage tray is mounted on the bottom of the engine, between the main bearing caps and oil pan.

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Design Responsible Engineer: Jodie Velzy/LT1 Lube and Vent System
Her insider's perspective: "Dozens of iterations of the wet-sump oiling system were evaluated before this one was selected. The goal was to ensure optimal performance during the high loads experienced on a racetrack. The LT1 wet-sump pan uses patented design features and highly developed baffles to prevent oil starvation by maintaining oil around the pickup tube during high-g maneuvers."

Water Pump
The LT1's water pump is made of sand-cast aluminum to minimize weight.

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Design Responsible Engineer: Michael Poisson/ LT1 Cooling and Thermal
His insider's perspective: "It's capable of delivering 66 gallons per minute to the radiator while still providing the necessary coolant flow to the oil cooler and heater core."

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