Here's a beautiful-looking 10 cc tether car racing engine that was submitted by Australian reader Simon Young. Simon has no knowledge of this engine's origins, and would like to know more!  He tells us that the engine appears to have been machined from castings - there are casting marks in the exhaust stack. The motor has a complex but beautifully made timer assembly. The cylinder liner is made of brass (sure it's not bronze, Simon?) with a two ring piston. The head is fitted with a steel adaptor from 3/8 to 1/4 UNF. Finally, the mounting holes in the lugs are threaded. 

Simon's impression is that this engine is American in origin due to the high level of manufacturing finesse and basic design parameters. It's not a production engine with which I'm familiar - perhaps it's another of the often superbly made racing engines produced as one-offs in the USA by talented individuals, particularly in the tether car field right after WW2. It would be great to have an idea regarding who made it! If you know, please get in touch through the email link provided!