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    A buddy of mine, who shall remain nameless looked this truck over before we purchased it and told me it was a decent buy. One of the comments he made was the all the smog stuff was there. So silly me I just assumed it was all good and take it on down to Randy at Precision Carburetor where it doesn't even get past the visual inspection. It was missing three minor things according to Randy. 

    The three emissions components were acquired from the local junkyard. Unfortunately I did not know how to hook up the Thermal Vacuum Switch. After getting the "Restoration Kit" from GM I found out that this truck does not need the Thermal Vacuum switch since it does not have an EGR valve for Thermal Vacuum Switch to control. Randy told me it needed it so I let him hook it up for me.

Thermal Vacuum Switch - Not required on Heavy Duty Emissions according to the documentation I got from Chevy. I think the documentation I have may be in error as it seems to be an integral part of the system.

Air Injection Pump (commonly known simply as a "Smog Pump") and the Air  Diverter Valve.  The pump supplies air to the diverter valve which feeds it off to the exhaust manifolds.

    The Light-Duty trucks came with two different emissions packages; Light-Duty and Heavy-Duty. For our Heavy Duty 350ci 4-bbl here is how it came from the factory.

• Positive Crankcase Ventilation (PVC)

• Evaporative Control System (ECS)

• Air Injection Reactor (AIR - Pronounced Smog Pump)

• Carburetor Heated Air (CHA)

The Light Duty

• Exhaust Gas Recirculation (EGR) - Light-Duty Only

• Controlled Combustion System (CCS) - Light-Duty Only

• Idle Stop Solenoid (ISS) - Light-Duty Only

• Early Fuel Evaporation (EFE) - Light-Duty Only

• Under Floor Converter (UFC - Pronounced Catalytic Converter) - Light-Duty Only Ha Ha