[luvbowties]

[QUOTE=utee05;6241097]You hit the nail on it, I do not have any experience with carbs at all. I have his rebuild book and think I can tackle it after reading up on how to do this. Pretty much I have learned a lot from owning this truck.


You said, "I have his rebuild book and think I can tackle it after reading up on how to do this." Since you have the book, 1st of all study the 'linkage pictures' and adjust/set yours accordingly/properly--not talking about pedal-to-carb linkages; but linkages like the choke--and other linkages--disallowing secondaries to open until choke is wide open(made that way by design).

Study them carefully, as I've seen some parts left off or set to intentionally cause secondaries to not open, for whatever reason like trying for better mpg(??). Sounds like it might not need rebuilding, esp. as it looks so clean that it probably has recently been re-built, just possibly improperly re-assembled. If it performs well exc. for the back 2 barrels not opening, you may very well have a simple, external fix. A parallel, I think, would be "if a tire is leaking air thru the valve core, tire may NOT need removing and resealing!...but just a valve core replaced."

Another good thing to do is to get a good-operating, like carb, and compare its linkage-positions to yours. Maybe get a buddy at a parts house to let you bring yours in and just compare it to one of his rebuilt/new ones from his shelf. You'll possibly immediately see a distinct difference[and the problem]; and should you find the culprit, buy your buddy lunch one day--could be $ well spent PLUS increasing your friendship!

HTH, & loving those quadrajets--'closest thing to fuel injection in a carburetor'[NOT my constructed statement, but one I kidnapped from another poster with whom I totally agree]!
Sam