Been fighting this issue for some time now. At speed (50-55 mph), when testing, my engine stumbles and bucks and stalls out when it encounters hills.
From idle, and while parked, I can rev the engine up to any speed with little or no stumbling. Sounds perfect. My driveway, however, is about a 6% grade. If I cruise up the driveway at or around idle speed, it will go all day long without a hitch. If I give it gas, though, on the same hill, it will stall and die. Restarts okay, but dies every time. I can sit parked and rev the engine on the same hill with zero problem and no stalls.
Specs: I added a Carter YF (exchanged out my Rochester), but it was doing this behavior before then. The Carter made this engine run like a top (while parked, that is). I have changed out the plugs, wires, condenser, and coil (added a ballast resistor). I also have a completely buggered exhaust system. I suspect leaks from the pipe that connects to the manifold all the way back. SWEET and I managed to explode the muffler (already split at the seams) while road testing it at hard acceleration on flat road. Ears are still ringing. I replaced the head gasket a few months ago, and replaced the exhaust manifold gaskets. I also added the missing manifold heat spring (which has never worked, to my knowledge).
This truck has been in a state of repair since I bought it a year ago. It has never had a true road test, though I have taken it on a few 4-milers before. Nothing with hills.
I have searched the forums and found everything from condenser to carb rebuild (float level check) recommended. Was hoping that, with this specific set of parameters, someone out there has seen the exact same behavior and knows how to cure it.
Thanks for any ideas.
