Vacuum advance problem
Hello everyone, i have a problem i was hoping someone could help me out with. I just purchased a 1970 chevy c10 with a 350. Only mod done to the engine is a holley 600 carb. I just purchased the truck so i dont know many of the specs on it. But here is my problem, the truck was running great however i am getting horrible gas milage, i know its not a prius but im getting around 5-7 MPG. So a friend said he just had the same problem and his was that the vacuum advance was connected to a ported vacuum rather than a manifold vacuum. Well mine is the same way so i moved my vacuum advance to a manifold vacuum port and now the truck stutters real bad like it doesnt want to run at all. It will idle but doesnt want to drive very well. If anybody has an idea please let me know. Thanks in advance.