* Specific Hemi engine: Chrysler has produced many different Hemi engines over the years, with varying displacements (e.g., 5.7L, 6.1L, 6.4L), power outputs, and applications. A small, older Hemi will be significantly slower than a modern, high-performance version.
* Vehicle it's in: The weight of the vehicle, aerodynamics, transmission gearing, and other drivetrain components all drastically affect the top speed. A Hemi in a heavy truck will be much slower than a Hemi in a lightweight sports car.
* Modifications: Aftermarket modifications can significantly alter an engine's performance. A heavily modified Hemi can achieve much higher speeds than a stock one.
In short, you need to specify the *exact* Hemi engine and the vehicle it's in to even begin estimating its top speed. Even then, top speed is rarely the best measure of performance. Acceleration (0-60 mph time) and horsepower are generally more relevant metrics.
