1980 C10 Custom Deluxe sputters at 35 mph

[MacAgent]

Help needed! My C10 is bogging/sputtering at 35 mph and when I let off the throttle, the pickup seems fine and will advance and do repeat at 45 mph.

I’ve changed out the plugs, wires, distributor, new fuel pump, blew the fuels lines out, and replaced all vacuum lines and fuel filter going to the carb, and the 2 barrel Rochester fully rebuilt.

Issue happened before all the changes and continues after. Put a clear fuel filter and with hood off and driving I observed the fuel dropping a little when hitting the throttle and experiencing the bogging/sputter. I’m at a loss in what to do next. Any advice is appreciated.

 

[fast 99]

Does sound like a fuel issue. Was fuel pressure AND volume checked? Do that first.

Have run into bad pumps out of the box, twice.

 

[MacAgent]

Yes, all is good and on my 3rd fuel pump in the last 60 days.

Could be timing?

 

[fast 99]

Anything is possible, timing over advanced could cause a lot of drivability problems. Check both total and initial. So you did check pressure and volume? If float level is very low could also cause issues. Although at cruise metering rods should down were they checked for movement through the bowl vent using a small screwdriver? What about the EGR valve, try disconnecting vacuum supply and road test.

 

[squaredeal91]

It Could be the fuel pump cam lobe be to worn to pump adequately Or it's sucking air from somewhere. Maybe try an electric pump inline as a test. Or pull from auxiliary tank with your current pump with one single hose strait to auxiliary tank.