re: Timing Vacuum Retard

[whs70@cc.bellcore.com (sohl,william h)]

Rod B. asks:
>I'm trying to figure out what the purpose of vacuum retarded timing
>is at idle.

The function isn't at idle, it comes into play when you lift
your foot off the accelerator.  The vacuum hose goes through a small
air switch which is closed when the accelerator is depressed, but if you
are cruising along and suddenly lift your foot off the accerator,
the switch is mechanically opened and the vacuum takes its affect.  
The purpose was strictly as an emmission control during 
deceleration.