Does anyone know the original part number for the valve circled in red in the attached picture? I can't find anything that looks like it in the 1972 printing of my 1970 and 1971 parts manual.

6949947-valves.jpg (43 downloads)
Scott Hollenbeck Administrator, Mustang 428 Cobra Jet Registry Owner, Muscle Car Research LLC 1970 Ford Mustang Mach 1 2006 Dodge Charger SRT8 1995 Chevrolet Impala SS