You have to watch this video! Thanks again to Samuel for the information.
OPERATIONAL V-12 DIESEL ENGINE THAT FITS IN THE PALM OF YOUR HAND.
This is not CNC technology; this guy made everything at home on his lathe and drill press. Took 1220 hours (a year and a half?) to make the 261 pieces. Note the end-loaded crankshaft into the block (like an Offy), 12 individual cylinder heads, TINY rods and pistons, dual "underhead" cams with pushrods 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!