The Detroit 12.7 and 14L engines are two of the most popular diesel powerplants used in heavy-duty vehicles today. Despite their similar sizes, they have distinct differences that make them suitable for different applications and needs. The main difference between these two engines is their displacement, or the size of the cylinder block. The Detroit 12.7 has a total displacement of 12.7 liters, while the 14L has a slightly larger capacity at 14 liters. Other than this key distinction, there are also other minor variations that help to differentiate one engine from another such as horsepower ratings, torque output levels and fuel efficiency ratings. As far as performance goes, both engines provide plenty of power for whatever vehicle they’re installed in but since the 14L offers more cubic inches it can be expected to produce higher horsepower numbers when compared to its smaller sibling – making it ideal for large trucks carrying heavy loads over long distances on a regular basis