Unknown carb part

[colohusker]

Okay, finally finding time to work on the old beast. Upgraded to an HEI, swapped trannies, and rebuilt and cleaned the Qjet carb. When rebuilding the carb, I noticed the module in the red rectangle in the picture, and it was hooked up to the electric wires, but not the vacuumn. I don't know what it's for, my guess is it was for a cruise control of some kind, but don't know if it's original or something a PO put on. If it is for a cruise control, there are no other components of the system in place that I know of.

So, all you truck gurus out there, help enlighten me on what this is?

[Livrat]

that is a factory fast idle soleniod.. part of the original smog system, they usually got tossed years ago...

[colohusker]

Thanks for the info, think this one will be tossed as well since it wasn't hooked up to anything and the truck runs fine and passes the Colorado smog test.

[425HP409]

The solenoid you are showing was a dual purpose one. It was to speed up the idle for reduced emissions and to keep the idle speed constant when the AC is engaged. I would keep it if I was you as it is nice to be able to idle with the truck in gear and the AC on at a normal level. The AC also works better at idle if the truck is not idling too slow. The compressor pumps better and the fan will pull more air through the condenser for better cooling with the idle not too slow.
Charles

[BHyatt]

Thanks! I was scratching my head about the same thing.

[jbristo67]

Originally Posted by colohusker

Thanks for the info, think this one will be tossed as well since it wasn't hooked up to anything and the truck runs fine and passes the Colorado smog test.

I thought it was to idle up your truck when your A/C was on. Is it an AC truck

[67shortie]

I have one of those in my tool box, keeping it one day when I finally get A/C in the truck.....

[StingRay]

Depending on vehicle they had some different applications. A/C idle up could certainly be one of them. My 72 had one and I was always under the impression that it was to eliminate dieseling. On the stock 307 it sure functioned that way. If you set the idle at the carb it would diesel like a bugger. If you set the idle at the solenoid it would activate with the key and it would idle at the set speed. Kill the ignition and the solenoid would deactivate and the throttle blades would fully close and starve the engine of air/fuel so that it couln't diesel. Worked like a charm too.

[425HP409]

That's right. I had forgotten about them also being used as an antidieseling solenoid. Depending on how you wire it up, it could be used for an anti dieseling solenoid or idle speed up solenoid. Either way, please dont throw it away!!
Charles