Just use the section view, the 'select other' and change transperancy options to select interior faces. A lid is just a lid, but do create it a bit realistic, meaning, if you use it as a flow entrance/exit, remeber the flow will enter/exit that face normal to the face. Usually, working with engines, you end up using either a dome shaped lid or a flat lid.
Stefan Hamminga
EngIT Solutions
CSWP/Mechanical designer/AI student