Stuart "Sun"

A Stuart Turner "Sun" twin cylinder engine, a fully enclosed, high speed design with stainless steel piston valve gear driven from the crankshaft.

Suitable for high pressure or flash steam, it was popular - amongst other things - for hydroplane racing.

Free to turn over, although curiously on test it would only run for 10 to 15 seconds before stopping, which will require further investigation (unless you're planning on extraordinarily short races...)

Complete with original Stuart Turner box and drawings.