1970 Carb Idle Control Solenoid

[Greg Gerard]

Are there any experts out there on the Carb Idle Control Solenoid or sometimes called a deceleration valve? My understanding it was put on cars with 4 speed and air in 1970. It mounts on the carburetor where the typical idle set screw is on the Quadrajet. Was suppose to keep the engine from decelerating to fast if you let off the gas to quickly. Maybe the extra drag from the A/C could cause the engine to quick?

I hardly ever see this on cars at shows. Is it peculiar to 1970 production year or maybe only part of the production year? Does anyone know the time period? Was it used on other cars besides the Corvette?

Is anyone reproducing this valve? Any guess on what a used one or NOS valve would sell for?
Thanks for any info / Greg

[Warren Friedrich (12139)]

Re: 1970 Carb Idle Control Solenoid

Greg:

I think that this item is sometimes referred to by other names as well, such as TCS (Transmission Control Spark) solenoid or CEC (Combined Emissions Control) solenoid.

1970 & 1972 models use the TCS system, while 1971 uses the CEC system.

[Jim Trekell (22375)]

Re: 1970 Carb Idle Control Solenoid

I have a 70 with turbo 400 and it has the TCS solenoid. This solenoid is mounted on the passenger side on the intake between the valve cover and the Q-Jet. It only controls vacuum to the vacuum advance cannister on the distributor. At normal operating temp there is no vacuum suppplied to the vacuum advance unit until the turbo 400 shifts into third. Another part of the system is the high temp function triggred by the temp sensor in the right cylinder head. It will allow full vacuum through the TCS solenoid if the temp gets to hot. I disconnected mine when brand new and it is still desconnected. Better gas mileage and never any heat problems in traffic.

[Greg Gerard]

Re: 1970 Carb Idle Control Solenoid

Warren/ Jim,

Thanks for your replies. The Carburetor Idle Control Solenoid or deceleration valve as some call it is separate from the TCS system. TCS was on all 1970 cars, both auto and 4 speed trans regardless of A/C. The idle solenoid was only placed on 4 speed cars equipped with A/C. It appears very little is known about it, there is some discussion on it in the archives. There is a picture of one on a 1970 LS5 car on the 1970 Corvette Registry site. I've put it in below. The valve replaces the idle set screw on the carb and has a set screw on one end and a small plunger on the end that rests on the throttle plate shaft. There are no vacuun or electrical connections to it, it is strickly mechcanical. I think the part number for it was 1114421.

I'm trying to see if anyone knows when it was discontinued and just how many cars it was used on. My guess it was on all cars that were equipped with 4 speed and air, but I don't think it made it very far into the production year. I have seen one Chevelle equipped with it. I don't think it is reproduced, and am wondering how much a used or NOS valve would cost.
R / Greg

[Clem Zahrobsky (45134)]

Re: 1970 Carb Idle Control Solenoid

i have seen this on some HD truck Q jet carbs

[Dick Whittington (8804)]

Re: 1970 Carb Idle Control Solenoid

Another name for it was a dashpot. I think that it was also used in other GM car lines of this era