* Design: The engine's architecture (V6, inline-6, etc.), the type of fuel injection, the compression ratio, the valvetrain design, and other internal components all significantly affect power output.
* Tuning: How the engine is tuned (computer settings, etc.) can greatly affect horsepower.
* Manufacturer: Different manufacturers will tune their 3.4L engines differently, leading to varying horsepower numbers.
* Year of manufacture: Engine technology improves over time, leading to higher horsepower in newer engines of the same displacement.
A 3.4L engine could produce anywhere from around 150 horsepower to well over 250 horsepower depending on the factors listed above. You'd need to specify the *make, model, and year* of the vehicle to get a precise horsepower figure.
