Adjustable Vacuum Advance
For example, from 1959 (Session 136) of the Chrysler MTSC.
In fact, its interesting to note that on some early Clean Air Packages (CAP) Chrysler did use a manifold vacuum connection to the vacuum advance.
This was to insure the leaner closed throttle mixtures were given enough advance to burn thoroughly when engine braking. The connection was made to the vacuum advance through a special valve. See 1967 Chrysler CAP System: Master Technicians Service Conference (Session 241) for more details.
This later was dropped for automatic equiped cars.
But normally Chrysler did not use vacuum advance at idle.
from Ignition System Analysis (Session 259): 1969 Master Technician's Service Conference
Ten years ago I too thought ported vacuum was an emissions related development. This came up in discussion now
archived. See "Carb Issues", scroll down to #11, 17 (me), and responses #13, and #19-22 where Shrinker et al set me straight.
For example, from 1959 (Session 136) of the Chrysler MTSC.
In fact, its interesting to note that on some early Clean Air Packages (CAP) Chrysler did use a manifold vacuum connection to the vacuum advance.
This was to insure the leaner closed throttle mixtures were given enough advance to burn thoroughly when engine braking. The connection was made to the vacuum advance through a special valve. See 1967 Chrysler CAP System: Master Technicians Service Conference (Session 241) for more details.
This later was dropped for automatic equiped cars.
But normally Chrysler did not use vacuum advance at idle.
from Ignition System Analysis (Session 259): 1969 Master Technician's Service Conference
Ten years ago I too thought ported vacuum was an emissions related development. This came up in discussion now
archived. See "Carb Issues", scroll down to #11, 17 (me), and responses #13, and #19-22 where Shrinker et al set me straight.