Fuel pump, collapsing rubber fuel line under high vacuum.
I did not see fuel filter on the list. On some chevy carbs there is a filter right where the fuel line enters the carb. In the carb itself, not sure if you have this or not. You may also want to follow the fuel line from the tank to the carb as a lot of times someone has added a extra filter somewhere along the way. Hope this helps, Tony, Joy and Cool Paw Luke
I ran into this exact situation years ago with a 76 chev 350. There was an in line filter and a small cone shaped filter that was right at the gas line intake to the carb. It had been in there so long I ended up breaking the gas line trying to get it out. It's a pretty cheap fix to try before going on to something else.Good luck.
I'm with Tony on this one. Assuming you have the Quadrajet, there's a filter inside the carb on the fuel inlet side of the fuel feed line. My 76 Barth also has one between the gas tank and the (mechanical) fuel pump. My money is on a clogged fuel filter.
Geno,you need to check the fuel pressure and fuel delivery volume.You might have a soft fuel line hose.Maybe your fuel tank cap is incorrect or defective.A non vented cap may be the problem.
I believe that I would go back to the accelerator pump. sounds like it it is ruptured or wore out and not giving that first squirt of gas when you accelerate. Also check the timing advance diaphram.
Geno,you could check the exhaust back pressure with a gauge installed at the y pipe. Maybe a mouse nest in the muffler?
Hi Geno, Wayne here from Australia. Had a similar problem about four years ago with our '88 Econoline 460ci. We had recently aquired our rig from an importer and after a couple of months found that while being great on the flat, lost power on any incline. The clue to the solution was extreme back pressure causing blowouts in the rusted body of the cat converter. Turned out to be a loose piece of metal inside completely blocking the outlet, 'only on an incline'. After replacing we felt as though we had wings. Just a thought. Cheers