Here is some more info I've gathered. It's reliability is slightly questionable, so you might want to double check its accuracy.


In 1970 all cars used the Cleaner Air System (CAS)(PCV valve, valve cover vent, etc. In 1970 California cars used the Evaporation Control System (ECS)(fuel vapor setup) in addition to the CAS system.

In 1971 the ECS & CAS systems were used in the other 49 states, while California cars went to the NOX system in addition to ECS & CAS. The NOX system includes special components for the transmission, a special camshaft with more valve overlap, and a 185 degree thermostat. There were 2 different setups available depending on manual or auto trans.

Manual trans = a switch on the trans sensed what gear the car was in. any gear below high gear made a solenoid cut off the vacuum from the carb to the distributor vacuum advance unless the temperature sensor indicated the underhood temp was less than 70 degrees.

Auto trans = similar to above, but used a speed sensing switch inline with the speedometer cable.

In 1972 the ECS & CAS systems were used in the other 49 states, while California cars went to the Orifice Spark Advance Control (OSAC) & Exhaust Gas Recirculation (EGR) system in addition to ECS & CAS. OSAC is a firewall mounted valve with hoses to the carb and distributor vacuum advance. EGR is a valve on the intake manifold with a temperature unit on the firewall. The EGR system had slight differences depending on what engine was in the car. (318 ported, 340 floor jetted)

In 1973 the ECS, CAS, OSAC, & EGR systems became standard on all cars. I'm not aware of any differences for California cars in 73.

In 1974 the ECS, CAS, OSAC, & EGR systems were still standard on all cars. California cars used a venturi vacuum amplified EGR setup.

Tav