I read somewhere sucking on the hose to the diaphragm of the distributor (as if I were a carburetor) would work to tell if a)it was an advance or retard dizzy and b)the dizzy's advance/retard worked. I sucked as hard as I could (though I can suck pretty bad sometimes) but saw not the least change in timing according the light&ball. I don't care about the retarded advance question and was really just wondering how my carburetor vacuum was working... But then maybe someone said the vacuum created by an able-bodied though medium-sized American male was not exactly the same as a 6-cylinder internal combustion engine? Any other way to check the distributor's end of the deal?