I have a 68 chevelle with a 355 and a holley 650 double pumper and a mechanical fuel pump. When i start it up it runs fine. After it warms up it starts acting funny. It starts to hesitate, the car shakes back and forth. Then when i slow down for a stop sign it wants to die and i have to give it gas and it sounds like its not getting enough gas. If it dies then its hard to start. I replaced the holley fuel pump with a edelbrock 6psi one and put a new earls fuel filter on. The pressure is usually around 5.5 to 6psi. It does jump around somewhat. Sound a mechanical fuel pump keep a pretty steady pressure? My cousin says the lobe on my cam could be worn or the fuel pump rod? Could this be the problem. I'm sick of throughing money at it. I just want to drive it. Im ready to just put it away and not even drive it. Its embarasing when your going down the road and its jerking back and forth and you can't keep it running.

thanks any help would be appriciated.

A mechanical pump will jump around a little because they have a pumping action.Do you have a choke on the carb,this will richen up the engine when it is cool,but when the engine gets warm and it opens up the engine will lean out.Check for a vacuum leak some leaks will get worse when an engine heats up,such as an intake leak or a leak at the base of carb.Unplug all your vacuum lines and plug all the vacuum sources let the engine get warm and see how it does.Check your timing,this can have one of the biggest effects of any engine.

Actually, have you checked your float level? Do you smell gas when the car stalls? Sounds every bit like a flooding condition. The very fact that it's hard starting when warm precludes a choke problem, unless it's stuck closed. As long as there is enough fuel in the carb bowl, the "jumping" of fuel pressure shoudn't cause this problem. Vacuum leak is a possibility. If you have a vacuum guage, hook it up to manifold vacuum and observe it when the engine is cold as opposed to when it warms up. Observe if the guage "jumps" around. It should remain fairly steady. Any chance of borrowing a carb from someone just for testing? Sounds every bit like a carb problem or vacuum leak.

Tried my other carb a 650 double pumper and it did the same thing but not nearly as bad. I had both carbs on my brothers nova and they ran perfect.