I just put in a new motor in my 72 GMC truck and the carb will not come down from a high idle. I don't have much good luck or experience with Holleys. I am also running a HEI dist. The vacuum advance for the dist is going to the vacuum port on the metering block. The Holley is a 600 with electric choke. I'm not sure what the model # is. The idle screw is backed all the way out. I have a light throttle return spring on it. If I push the throttle linkage closed by hand it will idle down, but as soon as I let go it will go back up again. Any ideas?

I have a light throttle return spring on it. You need to try a heavier spring. I have a double spring on mine. Works great. ;)

Check and be sure it's not up on the fast idle cam(on the passenger side of the carb). It has a separate idle speed screw and steps. If the choke is not FULLY open and the fast idle cam is not down on its base step, the fast idle screw will be controlling the idle speed instead of the curb idle screw.

Randy

I know it sounds stupid, but the same thing was happening to me awhile back and I finally figured out that one of the vaccuum lines on the baseplate of the carb that had been capped had fallen off.... graemlins/clonk.gif

Im a little late on this but do you have a 12 volt source going to your electric choke??? If you dont theres your problem