Project C7 Corvette Stingray: Introduction Part 2, A Closer Look at the LT1 Engine


Our Z51 package does things one better; we have the optional dry-sump system which is also found on the Z06. It uses a similar, super efficient variable volume pump on the pressure side which is fed from the dry sump tank. A high output scavenge pump is found in line with the pressure pump which sucks air and oil out of the pan and transfers it to the tank. This assures that the engine will always have a de-airirated constant supply of oil no matter how high the cornering loads are.

To validate the oiling system improvements, GM spent a lot of time doing extensive dyno testing. This included a dyno with 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 race tracks. The dyno can tilt up to 53 degrees and simulate lateral acceleration of up to 1.3 G's. 

Hopefuly this means the days of LS engines spinning bearings under hard cornering are over for good.


The part of the LT1 engine that received the most engineering attention is the new direct injection cylinder head. The head is cast from light and strong 319 aluminum alloy with a T7 heat treatment. The cylinder head was subjected to more computer modeling and simulation than any engine in GM's history to optimize the design.  Even with “old fashioned” 2 valves per cylinder and pushrods, you would be hard pressed to find a naturally aspirated engine with much better power density and efficiency than the LT1. 

The head has a huge 2.130 intake and 1.590 exhaust valves that are canted 12.5 degrees in the intake and 12 degrees on the exhaust and splayed 2.5 degrees for better flowing, more direct port geometry with better flow entrance and exit from the combustion chambers.  This is trick stuff learned from Motorsports experience over the years. Remember the revolutionary porcupine head on the Intrepid GTP car? That was the great grandfather of this head.


The LT1's combustion chamber geometry is the result of millions of hours of computer combustion simulation and physical testing. The result is the ability to run 11.5:1 compression on pump fuel.  

If you know your Chevy stuff, the first thing you will notice about the LT1 combustion chamber is that the intake and exhaust valves are reversed from their traditional positions in the chamber. This allows the intake port to have a straighter shot into the cylinder as the pushrod hole does not impinge upon its location as much. If you look at the LT1's intake port compared to an old SBC or even an LS3, there is an easy to observe improvement in the intake port geometry from this. 

You can see the direct injection nozzle in this picture opposite of the spark plug. For better atomization, which yields a more complete burn, the injector nozzle has six holes. The injector has a whopping 126 lb per hour capacity at 1450 psi which has some headspace for mods. Although the injectors seem huge, they only have the capacity for about 750 hp as the injection time is much shorter on direct injection vs port injection. 

The abilty to support 750 hp is good news for us, as the aftermarket will have a hard time working up replacements for this technology at first. The fuel is injected on the intake and compression strokes so none gets wasted on overlap. This also helps to greatly reduce hydrocarbon emissions. To overcome the compression pressure, the fuel is injected at pressures up to 2200 psi!

Injecting fuel directly into the 59cc combustion chamber provides a tremendous amount of in-cylinder cooling, allowing the super high 11.5:1 compression ratio on pump gas. The in-cylinder cooling of the intake charge also helps increase volumetric efficiency, and the charge will shrink as it cools, allowing space for more charge. 

When you look at the old small block Chevy and previous version of the LS, you will notice right away that the spark plug on the LT1 has been moved considerably and is now as close to the center of the combustion chamber as it can get with a 2-valve per cylinder arrangement. This really helps improve combustion stability with direct injection.

The combustion chamber itself is shallow with a low surface area to volume ratio for good thermal efficiency, due to less heated combustion chamber surface during the burn. The combustion chamber has a lot of quench area around the chamber itself for good turbulence of the compressed mixture as the piston comes to TDC. This, combined with a two-part direct injection strategy, helps to assure a complete burn of the fuel and air. Every bit of the combustion chamber geometry was designed to optimize combustion with direct injection. 


The LT1's pistons have a trough in them in the area of the direct injector between the valves. This is to keep more fuel in the area of the spark plug for better initiation of combustion. The pistons are made of a high strength hypereutectic aluminum alloy, feature a low friction polymer coating on the skirts, and have long wearing hard anodized ring grooves. 

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