Those cheap distributors have stamped out mechanical advance units that usually wears a lot faster than a quality unit with hardened parts.What Panic says is correct,you need to build an advance stop.This photo shows what I do on a V Hei distributor,same as the inline unit.Usually limit the vacuum advance to about 12-14 crankshaft degrees(trial and error with a timing light)use intake vacuum ,not the ported carb vacuum if doing an advance stop.
