The 4 hp expansion chamber on the Detroit Engine Works and Detroit Motor Car Supply Company (Sandow) marine engines were the same. Casting number 5BC2. I Don't mean to be discouraging but your probably going to have difficult time finding one of these. Your chances of finding a whole engine with maybe a few parts missing are probably better. Was your manifold missing or broke? The reason I ask is some of the marine style Detroit's were converted at the factory into stationary farm engines. Some did not have the expansion manifold. Do you have photo's of your engine you could post?