The 351W, or "Windsor" engine, manufactured between 1969 and 2001, is a member of Ford's 90-degree eight-cylinder engine family. Not to be confused with Ford's 351 "Cleveland" engine, the 351W gets its name from Ford's Windsor, Canada, plant, where it was briefly manufactured.
The quickest way to identify a Ford 351 Windsor engine is to count the number of bolts on the valve covers. The valve covers are located on the top of the engine, one on either side of the air cleaner, and each will have six bolts. If the valve cover is removed, you will see "351" stamped on the cylinder head in the valve valley. This method works if the cylinder heads have not been changed with those of a similar engine.
The 351W casting number is located on the right side of the block, about halfway down, facing downwards. The code will be a combination of letters and numbers -- for example, "E3AE." In this code, the E represents the decade number and the 3 represents the year. This engine was manufactured in 1983. C represents the 1960s, D for the 1970s, and so on..
The block casting number does not necessarily identify the engine as a 351W, and a combination of different identification methods is recommended to positively identify it. Use the valve cover method along with the block casting number. Another trick is to look at the thermostat housing, located on the front of the block. On a 351W, the top bolt can be easily accessed and removed using a socket wrench. On similar Ford small-blocks, like the 302, the bolt cannot be easily accessed with a socket.