what is the difference...
 

what is the difference between the 12 and the 24 valve cummins engines?

12 valve has 2 valves per cylinder, and utilizes a mechanical fuel injection system. The 24 valve has 4 valves per head for increased air flow, and uses an electronically controlled injection pump. Those are the main differences.

Does the 24 valve have more power since it has twice as many valves?

It has more power, but not just due to its extra valves. As the years have gone by, engine have become more powerful, and I am using stock configuration for power levels.

This site has a lot of information about the Cummins engines, from 89 to 02

Oh ok, thanks for your help