Can you describe the process by which a modern internal combustion automobile engine is designed?

Well, I say it’s designed to function as certain shape to fit a certain area, once that’s all worked out it does this

Imagine you are working at GM, etc. First you would gather requirements: power, torque, fuel consumption [Mech Engr]. Then you would look at previous designs. Hopefully you will have taken thermodynamics and combustion courses in college [Mech Engr], so you could calculate or estimate what the new engine ought to look like. A big company should have the right software to model this new engine and predict the performance. If OK, then you would create engineering drawings and get prototypes built [machine shop]. If not, maybe you would need to troubleshoot the design. Was there a temperature problem [Thermal Engr]? Can the electronics support this design [Elec Engr]. Bad air flow? [Fluid Dynamics]

So there is plenty to do to get a new design out, and plenty of design iterations.

The engines in cars today are the result of close to 100 years of evolution. Basically a drawing of the engine is entered into a series of mechanical drawings using software on a computer. It takes a drawing for each part. The drawing also refrences details about the part like the material it is to be made from and wither the part is forged, machined, or stamped. The drawings are sent to various suppliers who make the parts. At the auto factory the parts are gathered, assembled, and the resulting engines are tested.