Well good to hear theres more power. Ya gotta go back to the basics. Vacuum leaks, intake leaks, rockers set properly, good plugs, wires, cap and rotor not burnt, coil wires connected properly, good coil, plug wires on correctly and at last the fuel delivery, good filter, proper pressure thru out 5 to 7 PSI constant. Timing correct.....once ya get that figured out then you can play with the carb...sounds like the 670 will be much better...
Terry