[Apache'71]

Originally Posted by donw1986

Glad it works good for you, just wondering what is a TRC, my carb had a throttle position sensor and mixture control solenoid

It's the Throttle Return Control Valve/Actuator. The valve is a vacuum canister on the manifold that operates a the actuator that's mounted on the factory carb.

Here's what I found it does:

Two different throttle return control systems are used. The first is used from 1975 to 1978. It consists of a control valve and a throttle lever actuator. When the truck is coasting against the engine, the control valve is open to allow vacuum to operate the throttle lever actuator. The throttle lever actuator then pushes the throttle lever slightly open reducing the HC (hydrocarbon) emission level during coasting. When manifold vacuum drops below a predetermined level, the control valve closes, the throttle lever retracts, and the throttle lever closes to the idle position.

The second TRC system is used in 1979. It consists of a throttle lever actuator, a solenoid vacuum control valve, and an electronic speed sensor. The throttle lever actuator, mounted on the carburetor, opens the primary throttle plates a preset amount, above normal engine idle speed in response to a signal from the solenoid vacuum control valve. The valve, mounted at the left rear of the engine above the intake manifold on the 6-cylinder, or on the thermostat housing mounting stud on the V8, is held open in response to a signal from the electronic speed sensor. When open, the valve allows a vacuum signal to be sent to the throttle lever actuator. The speed sensor monitors engine speed at the distributor. It supplies an electrical signal to the solenoid valve, as long as a preset engine speed is exceeded. The object of this system is the same as that of the earlier system.

Even though CARB compliance probably requires that I maintain this, it's probably redundant with all the things the Atomic is doing electronically.