These early engines had displacements of 5.9 liters with 12 valves, meaning one exhaust and one intake ... Third-Generation 5.9-Liter 24-Valve (2002 - 2007) Midway through the second-generation ...

That all changed in a big way with the introduction of the first-gen 5.9L Cummins in 1989 ... which decreased intake air temperatures, improved fuel economy, and increased power output.

These early engines had displacements of 5.9 liters with 12 valves, meaning one exhaust and one intake valve ... both the late second-gen and the third-gen 24-valve Cummins engines are considered ...