`V8s == How come there are no v8 engines for class 8 trucks in North America?   :There were 8V92 Detroits and 8V92 ``Silver`` Detroits that were well-renowned motors for Class 8 trucks.  I believe that currently the educated thought is that inline 6-cylinder engines can fit into a tighter space profile with accessories such as air compressors, allowing truck hoods to be sized smaller.     ::The reason might be that the inline 6-cylinder engines are  obviously  of a much simpler configuration since there is only one bank of cylinders verses two banks of a ``V`` design.  Also, there are significantly fewer high-precision parts in a 6-cylinder engine verses an 8-cylinder engine (e.g. pistons, connecting rods, valves, injectors).  Routing of intake air and exhaust gas is simpler in an inline engine verses a ``V`` type engine.  Thus, an inline 6-cylinder is easier and less expensive to design, manufacture, and maintain than a V-type 8-cylinder.  Additionally, I believe the inline 6 design is more efficient than the V8 because there is less heat loss.  Four-cycle V8 diesel truck engines were manufactured for class 8 trucks by both Caterpillar (e.g. the 3408) and Cummins (e.g. the 903) up until the early to mid 70's.  Detroit Diesel stopped making 2-cycle engines for motor vehicles because those engines were incapable of meeting the more stringent exhaust gas emission requirements.—Preceding unsigned comment added by   04:53, 11 August 2009  == `