this all my opinion only, but i am guessing that the problem you notice at lower speeds and rpms is probably still a problem at high speeds and rpms, you just don't feel it as much. What condition is your timing chain/gears, distributor, points, vacuum advance in? How about the fuel pump? I had one 230 six that the fuel pump lobe on the cam was worn out. There are so many things to look for, I hope I give you something helpful. Check the carb for vacuum leaks while the engine is idling by spraying the outside of the carb lightly, in short squirts, with a can of ether starting fluid. If the rpm goes up when you shoot a certain place, you're leaking vacuum there. check the routing of the fuel lines leading to and from the fuel pump, especially the one from the pump to the carb, as it has to run around the exhaust manifold somewhere. Read your spark plugs to see if your fuel mixture is good, you may be loading up at low rpm's. Check your plugs, wires, cap and rotor. An old plug wire or cracked cap will do it every time. hope this helps,,,,,,,, Cory
