Dunno...You'd need to find a vacuum hose chart. But you shouldn't really need the extra hose for the PCV system to work. I'd plug it until you can find out where it goes. As long as the one to the intake is connected, and the valve functions, it should work.
after way too many years of working on ford industrial 300's, I can answer this question. Ford in their infinate wisdom used the same pvc valve for multiple applications. The top port is used for some emission control operations, for those other uses the top port is simply blocked off. hope this helps
Thanks for the input oldschool63! Its been bugging me for months about thoses 2 ports. Do you know which vehicles might have used both or the other port, or why?
Funny that Haynes does not mention this - unless I've missed it.
mrstace84 - there are some other threads regarding PCV and re-routing the intake FROM cyl 8 TO the vacuum plenum (tree) to avoid fouling.. sorry I don't have the info handy but will post later if needed.
Not sure if it applies to your 84 truck though ..mine's a 1989.
sorry it took so long to reply. As for that upper port being used, it all depended on where the truck was built for and what type of emissions it had. I've seen the same year and model with different routings and for no real reason i could determine other than the emission package it was sold with. Or it could just be a Ford thing! : )