It isn't CNC technology; this guy made everything at home on his lathe and drill press. Took 1220 hours (year and a half?) to make the 261 pieces.

Note the end-loaded crankshaft into the block (like an Offy), 12 individual cyl heads, TINY rods and pistons, dual "underhead" cams with push-rods to rockers in the heads.

And, he did break-in using an electric drill driving the crankshaft!

Even if you're not an engineer, you'll love this