In 98 there was this old machinist who made a 1/8th scale, IIRC, working replica of a Rolls Royce Merlin 12 cylinder engine - actually it was the Packard built version made under license in the US for the P-51 Mustang. They differed primarily in the direction of rotation. (The British used propellers that turned the wrong way
.) It was supposedly 100% representative of the full size version he copied it from. I was heavily into the 1/4 scale radio control airplane hobby at the time and was keeping an eyeball peeled for such an engine. But, he made it because it was on his bucket list and not because he intended to market it. Had he made it 1/4 scale he'd have had a gold mine.