1941 was the first year for the 235. It was low oil pressure, babbitt rod bearings, and looked very similar to the 216. Later on they changed the intake manifold runners to round in cross section and changed to a short tappet side cover. Another change was to insert rod bearings and full oil pressure. Others can pin point the years of these changes. You need to look at the various casting numbers and stampings to verify exactly what you have.
