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Some information I found on-line, not sure about closer spacing, but larger valves for sure.
Integrated Cylinder Heads/Exhaust Manifolds: the LFX’s new cylinder head design has a revised intake port design that enhances airflow to the combustion chambers. Larger-diameter intake valves are used in the heads and work in conjunction with new, longer-duration intake camshafts to provide the engine’s boost in horsepower. By using larger valves and holding them open longer, more of the air is pulled into the combustion chamber, for a more powerful combustion. The exhaust manifold is incorporated with the cylinder head, which saves weight, reduces complexity and helps promote a quicker light off of the catalytic converter, which further helps reduce emissions.
Direct Injection: direct injection moves the point where fuel feeds into an engine closer to the point where it ignites, enabling greater combustion efficiency. It fosters a more complete burn of the fuel in the air-fuel mixture, and it operates at a lower temperature than conventional port injection. That allows the mixture to be leaner (less fuel and more air), so less fuel is required to produce the equivalent horsepower of a conventional, port injection fuel system. Direct injection also delivers reduced emissions, particularly cold-start emissions, which are cut by about 25 percent.
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