According to the book, "The Complete Ferrari" by Godfrey Eaton, the "E" in the name has come to refer to the type 128E engine. This was a newly designed engine with coil valve springs instead of the "mouse-trap" style valve springs used on earlier versions of the 3.0 liter, type 128 engine. This engine had new cylinder heads with the spark plugs on the outside of the engine, instead of in the "V" of the engine. Essentially now on the exhaust pipe side instead of adjacent to the intake manifold. This was to allow for better airflow through the head and larger intake valves.