The Ford Flathead V-8 engine powered Ford and Mercury vehicles from 1932 to 1954. The Ford Flathead is a valve-in-block engine and the valves open adjacent to the combustion chamber, rather than from the top, as in later engines. The four different V-8 flathead displacement sizes between 1932 and 1953 are 136, 221, 239 and 337 cubic inches.
Count the number of studs on the cylinder heads. According to Van Pelt Sales’ Ford Flathead Specifications web page, the count is as follows: all 136-cubic-inch engines have 17 studs, all 337-cubic-inch have 24 studs, 1932 to 1937 221-cubic-inch engines have 21 studs, 1938 to 1948 221- and 239-cubic-inch engines have 24 studs. The 1949 to 1953 239- and 255-cubic-inch engines have 24 bolts rather than 24 studs with nuts.