Obviously there are some people here who know nothing about how a raw casting gets made into an actual usable engine block. You have six major surfaces that need to be machined flat and square (or at 45°). This means you cannot machine the whole block in one setup. Without sophisticated fixtures to precisely locate and hold the block from moving, and a multi-axis CNC mill (at least 4-axis), you will go nowhere. So now we have investments in fixturing, tooling, and CNC programs. Also, don't forget you normally have to make the main caps, and the have to be fitted to the block before you can even line-bore the crankshaft bearings. You'll need dozens of special tools, including gun-drills for many the oil passages. Maybe modern deep hole drills with thru-the-tool coolant would work in place of the gun drills. But whatever, it's going to be expensive and special tooling.
