If the dwell is 60 degrees the engine won't run- - - - -the points will be closed all the time. On a 6-lobe distributor cam, there is only 60 degrees of separation between the high spots on the cam. Now, if the dwell is 60%, like it's supposed to be on some distributors, it will be close to 40 degrees.
If the idle speed is adjusted correctly, there should be no vacuum on the distributor line. As the throttle is opened, a port is uncovered by the throttle plate that begins to advance the timing just off-idle. On a stovebolt distributor you don't need a timing light- - -you can watch the distributor housing start to move as the engine speed is increased.
Jerry
