If you're looking to engineer a totally new never built design...good luck! Do you really think that you can improve on the designs and experience of manufactures like Cummins, Isuzu, Deere & Caterpillar that have been building successful diesel engines for many years? With all the millions and billions of dollars spent, even they have poorly designed engine models make it through engineering to hit the market.
Actually, YES.
People do it all the time. Who do you think WORKS for cummins, isuzu and deere? Human beings that are engineers!
Most the people at cummins etc REFINE existing idea's not come up with completely new ones. Its an evolutionary process.
Most engineers in the auto world dont focus on blocks per say, the magic is in the crankshaft, cylinderhead and induction package.
Your real bad asses build "dual plane" cranks and things like that for standard blocks so you can take stock junk and make it into "race car" quality items. If you think OEM design cant be improved upon. well you are just an idiot then.
If you want to design and build your own engine you will need the engineering knowledge and the practical application skills to bring to life what you envision.
Most engine designers dont have any real world mechanical skill. Everything they do is theory and on paper.
Then this design is given to the men in the trenches, the guys that can make the castings, plugs whatever.
I would say by far in todays world the easiest route would be to pursue engineering school, and CAD/Machining classes.
If you can draw in solidworks and run a CNC machine you can design and build anything and everything you damn well please.
Castings adn extrusions are just ways to keep manufacturing cost down, but a one off billet block would honestly probably be cheaper than creating a mold for one and casting only a single unit.
Pursue your passions, tell everyone else to shut the **** up.
When i went to harley school as a kid we had a dyno day. Some guy showed up with a Knucklehead he had completely made himself by doing his own sand casting in his garage. Laid down 100hp to the rear wheel. Anyone that knows harleys will say thats impossible on a knucklehead. Which it is...he grafted evo valve geometry into a knuckle casting. Why? i dunno..but it was cool as ****!!!
This world is driven by PEOPLE who do not accept what is commonly available as "good enough"
if no one could do better than what has already been done, we would at best all be driving model A's