years ago I had an '83 27' Class C Tioga with the Ford 460 and 4bbl Holley built for Motorcraft carb. I struggled for quite some time with what appeared to be vapor lock (But wasn't) - loss of power when hot randomly and intermittently.
In researching that issue, I found the best help here and on Ford-Trucks.com forums. Someone here (I don't recall who - may not even be here any more) provided a fuel system diagram - when I have more time, I'll try to do a search far enough back to find it).
Edit - just did a forum Advanced Search here for
Keywords: Ford 460
Message Author: gkainz
Date Posted: selected "Archive - over 1 year ago"
and it returned 9 threads (quite quickly, I might add)
My coach had 1 tank, installed by Tioga, I assume, with no in-tank pump. It had an electric pump installed on the frame rail immediately in front of the tank (at the rear of the coach) that pushed fuel to the carb. Just before the carb was an aluminum "block" that had fuel line in, 1 fuel line out to carb, and 1 fuel line out that was the return to tank. As it turns out, this "hot fuel diverter" (I think that's what Ford calls it) would return most of the fuel to the tank and starve the carb when hot. Found by putting an external fuel pressure gauge in line at the base of the carb to try to figure out what was going on.
I never found a replacement for that diverter valve, but solved the fuel supply problem by adding a mechanical fuel pump back into the engine block (parts guy pointed me to a Lincoln 460 that still used the mechanical pump then), and a fuel pressure regulator that kept the pressure at 8 psi at the carb, if I recall correctly. One risk was that if the diaphragm on the mechanical pump failed, the electric pump could pump fuel straight into the engine oil pan.
Anyway - I know that doesn't help answer your questions, other than "been there, done that!"
Good luck!
