mild steel is 2 times stronger than cast iron and 10 times the fatigue life.
Stop right here. Go to homemodelenginemachinist.com and lurk their forums, then build a small ICE from scratch, only after you have done this can you even think about making major engine parts from scratch. Mild steel may be stronger than cast iron but if it's Cold Rolled then it's stressed and you can't do anything with it. You need stress relieved Mild steel which you can't afford (of your own admission). There is a reason that engineers design engines in aluminum and cast iron, and if it was just for cost effectiveness then they wouldn't appear in race engines (which they do).
thanks for the link! its very interesting.
hot rolled mild steel is good enough. race engines dont use steel because welded crankcases are not allowed by the rules. whats the point of using cast steel? really thin castings is very hard to do. better to cast aluminum in thick sections. if welding was allowed they would all be using friction stir welded aluminum cases.
i can cast an aluminum crankcase if needed. but then whats the point? id rather use a subaru.
the tvr cerbera speed 12 used a welded steel crankcase and it worked. but as tvr noted its not amenable to high volume production. but with the current welding technology, low volume production is feasible. with cnc machines economy of scale dont mean anything any more.