So you are setting them between 0.4 and 0.5mm? That is about right for
an unworn distributor. But less may get you closer to the dwell you want.

Yes, the dwell meter measures the proportion of time the current flows through
the coil and divides it by the number of cylinders (normally by using different
scales on the same meter). If it is not running it will either be 360° or 0°
depending on whether the points are open or closed. Neither is a helpful
or valid reading. So you gotta run the engine. The tach function is a
counter which counts the number of times you get an ignition pulse in a minute
and divides by half the number of cylinders to give you rpm. Fairly similar
circuitry so they are usually combined in one instrument. I haven't bought one
in a long time (they tend to be fairly durable) but I would bet that the same
thing has happened to them as to electronic tuners for musical instruments -
they have not only gotten cheaper, but better also.
--
George Downs, Bartlesville, Oklahoma, Central US