I have a 1987 F250 with a 1986 460 engine. It acts like it is starving for gas. It runs but barely. I just changed the fuel filter that is attached to the carb, this helped some but still does not perform properly. When i had the filter off, i pumped some gas out of the hose, there was not much pressure, it just flowed out. The vehicle actually started, i am now wondering if it is possible that there may be 2 gas line inputs? It i switch tanks it does not change anything.

 

Not for sure about this year 460 motor, but I'm assuming this is an EFI. If it is, I would start with fuel pressure and then perhaps there is the in tank pump and the outside frame rail pump. Perhaps one is failing....If it's not able to keep the psi up, then that would be the problem.

 

It is not an EFI, regular carb.