Not being critical, just wondering. Is it because it was originally an agricultural/tractor engine that had the engine almost as part of the frame and therefore required more structural rigidity?

 

Not real sure but I think it had something to do with controlling temperatures and for more rigidity of the block structure.

 

My understanding is that it doesn't control temperatures as well (at least at the extremes).

I think the 5.9 had a pretty strong block already, so there probably wasn't a need to go beyond that.

 

It is my understanding the the QSB 6.7 (offroad 6.7) is simply a stroked 5.9. This made the engine somewhat taller than the 5.9. However, its cylinders are NOT siamesed. DC insisted that the 6.7 had to fit into the existing Dodge engine bay WITHOUT forcing major sheet metal changes. Thus the DC engine is bored, stroked, and siamesed. If the DC 6.7 turns out to be a higher wear rate engine, blame DC.