1968 GMC 250 Inline 6 4.1L Chugging

[Jason Banks]

I've held off commenting, but my 1968 with 250 has basically the same problem.

I've always thought it was a fuel problem. I have HEI and have rebuilt carb a couple times. Truck also has a new fuel sending unit/pickup and the tank doesn't look like it has trash in it.

I loved hearing 72c20customcamper say that it was a fuel line collapsing because the symptoms he was describing is just like mine, slight incline, near WOT trying to go 69-70mph on the highway with 4:10 rear gears. It starts bucking and you have to let off the gas and slow down for it to get better. Doesn't always happen, you can run for miles at about 70 then it just chokes.

Interested to hear what you find out. I'm thinking I'll inspect the rubber lines, but I know I've replaced those in the past. Might try something stiffer, like some PTFE lined AN line. I've been neck deep in my other truck and kind of neglecting the other one...