It only took me a day to make my 1405 edelbrock *(Adapt-O-Brock) linkage to work on my 79 C10's "new"305 I installed--the same problem as yours,after getting a V8 accelerator cable (mine was a six cylinder)and installing it--I couldnt get it to return to idle--I had to remove the bracket that holds the cable and file the holes out making them more like slots,and pused it closer to the carb,allowing the throttle to close completely--I had only about a 1/16 of an inch to spare,I had to use one of the closer holes in the throttle lever to make it work.I had one of those tiwan cable holders for the detent and accelerator cables, but I couldnt use it because the bolt that holds it to the carb is the outer rear bolt.which has no bolt in it because my carb is on the quadrajet manifold with an adaptor,and it uses the inner bolts to hold the carb on,and you cant put a bolt in that outer hole--the intake is in the way.I spent more time hooking up those cables than it took to install the motor /forums/images/graemlins/angryfire.gif--ended up using a hose clamp with a 3/16 bolt brazed to it to hold the detent cable,and I had to put a light helper spring on it to help it return to the normal position.I hate messing with throttle linkages and detent cables--if you jerry rig it too badly,your life is at stake if it sticks wide open,and its dangerous to pull over on the highway around here to fiddle with stuff like that--its the number one reason I dont like aftermarket carbs,they NEVER fit the original linkage correctly,you always need to make adapters,remove EGR valves that are in the way,and engineer a new linkage and detent cable hookup--and why is it they never give you those damm "ball joint" things that snap onto the cable and go in the throttle lever--I was using the end of an old sparkplug as a substitute til I coul get to the boneyard(10 bucks at a speed shop--they can keep them!).
You may want to be sure the secondary butterflies arent sticking open,they might be rubbing on the base gasket,or the adapter,if you are using one--the choke also has a fast idle cam that could be sticking,or choke not opening all the way,the accelerator pump can make the throttle want to stay open if its sticking in its bore also.I wouldnt run too stiff a return spring,because that will tend to "egg"out the throttle shaft bushings. Hope this helps you some--I know I was ready to go buy a quadrajet at the boneyard and ditch the edelbrock carb--I was pretty frustrated by the time I re-engineered the linkage and cables--and had a very sore back from bending over it all day----. /forums/images/graemlins/crazy.gif
