[richard rink]

MOT, you mentioned that the timing is set "by ear" and that the loadamatic distributor is equipped with the Pertronix ignition. I am presuming that the vacuum connection between the port on the carb and the distributor is in place. You have not mentioned the idle speed, i.e., fast or slow or how the engine reacts when you "goose" the accelerator. Is there hesitation/stumble or a quick run-up? Have you measured the vacuum while rotating the distributor to advance/retard the timing? This will have an effect on the vacuum.
Richard