MSD Atomic EFI on '79 K30 in Cali

[layinrocker65]

Fellow CA resident here. Unless your buddies with the smog guy, it’s never going to pass visual inspection. Your best bet is to return it or register your truck in a smog free county. The Bay Area smog guys will fail your truck for any visual problem.

[mattcrp1]

Call the referee hotline and ask to get a call back, talk to the referee and explain the situation. There is on in Livermore and they should be able to point you in the right direction.

[donw1986]

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

[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.

[donw1986]

I think you will be ok with carb, by the way i did just take mine to the local smog guy near me, i did not go to the smog ref

[ZacharyDouglas1992]

I can't believe I haven't stumbled across this post sooner. I have an '83 GMC K3500 that is just a smog nightmare. The original Rottenchester was ruined in the body shop as it it was just totally contaminated with bondo dust. I ordered a replacement carb and I cannot seem to get the truck to do everything right at stock timing. I can get it to idle like a dream, or perform under throttle, but definitely not both. I can get it to run fantastic with enough timing (16 deg) but I have to be at 4 deg BTDC for smog purposes. I have toyed with the MSD atomic idea since it was more than twice the price it is now. The only thing that has been scaring me lately is the addendum that speaks to the AIR system. (mine has 1 ton CA emissions for 83, so the AIR tubes go straight into the manifolds, and the truck has true dual exhaust with no catalytic converter.) Your post gives me a little more hope that I can make this work.

I would like to keep the dual tank functionality too, as I would imagine even with the FI my mileage will be 11-12 on the 454. Maybe that can be accomplished with an external pump after the valve, but I am not sure what that would mean as far as running a return line.

Any of your feedback is appreciated. I am nearly frustrated enough, and encouraged enough by the posts here, to try it.