This is a very interesting radial engine, the 1932 Guiberson diesel. This is an early engine with what appears to be a single intake valve and fuel injection at some point in the intake port. The exhaust may have been thru a port or reed valve in the backside.
The later versions had two conventional valves and also used fuel injection. The company ran one goverment engine tests for one thousand hours which it passed without any pro-blems. They were quite sucessful and were also used in tanks and landing craft during WWII.