make sure your distributer has a good ground! pull the cap,turn motor by hand until rotor is pointing to # 1 wire on cap,pull distributer and clean area where it contacts the block and also check your ground from block to frame,frame to body by removing and cleaning with brake cleaner and wire brush. my forklift was acting up(chrysler ind. flathead 6) driving me crazy and after cleaning the grounds it stopped acting up. if you have solid lifters make sure they are not gummed up. have you done a compression test yet? that will tell you what the valves are doing. if it has fresh plugs and your using starting fluid and valves are operating properly (meaning you have correct compression) ignition is only thing left.
