Which of the following is NOT found in heavy duty diesel engines?

The option indicating "parent bore" is the correct choice because it refers to a specific engine design feature commonly found in lighter-duty or smaller engines rather than in heavy-duty diesel engines.

In heavy-duty diesel engines, components such as wet sleeves, dry sleeves, and cast iron blocks are prevalent. Wet sleeves are utilized to enable easy replacement of the cylinder liners and to manage heat better, while dry sleeves provide a solid cylinder wall that separates the combustion chamber from the coolant. The cast iron block is robust, offering the durability required for the high stress and loads typically associated with heavy-duty applications, making it ideal for heavy-duty diesel engines.

Thus, the characteristic of a parent bore, which usually indicates the original cast iron block where the cylinder is machined directly into the block without liners, does not apply to heavy-duty diesel engine designs that prioritize interchangeability and easy maintenance through liners.