Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Edelbrock Quadrajet 1904 idle speed screw non-functional

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sbc357-75camaro:
Hello all,
          Just had my Edelbrock 1904 Quadrajet rebuilt and re-bushed with all of Cliff's kits and parts, but we've run into one problem. My 357 small-block Chevy, which is built bone-stock, is idling too high at 950 RPM. When we try to turn the idle screw down, it has no effect at all on the RPM's. Now, the idle screw is completely unseated, and we have nowhere else to go! The carb performs beautifully; great road manners, acceleration; everything else seems just fine. Choke comes on cold, comes off easily; got the fast idle RPM set low at around 1100 RPM, comes off normally after about a minute on a hot day....Throttle response is excellent.....Idle mixture screws are functional; when adjusted, engine responds to leaning/enrichening adjustments.....Anyone have any idea what might be the problem?
                                   1975 Camaro
                                   357 Chevy small block (bored .040 over)
                                    original style Crane cam shaft, Chevy 929 cam,
                                    .390/.410 lift
                                    duration at .050 is 195 - 202
                                    Dish style pistons, 8.5-1 compression ratio
                                    Edelbrock aluminum intake with EGR valve functioning
                                    engine has high vacuum
                                    initial timing is 12 BTDC

           We tried backing the timing down to the stock 6 degrees, but still no change in idle speed screw not working. My mechanic said that the primary throttle shaft is straight and the new bushings went on easily with no issues. Throttle shaft and throttle plates had play in them before rebuild; they don't now...
            Before the rebuild, the idle speed screw was not as sensitive as when it was new; now it does nothing at all. Idle at Park or in Neutral is 950, which is too high.  Help! Thanks guys, JT

Kenth:
Unhook the throttle rod/cable and see if you can close the throttle blades completely.
Check that the secondary throttle blades are completely closed.
Check the flange gasket for leaks.
Check any vacuum check valves or hoses.

Cliff Ruggles:
Are you using vacuum advance at idle via manifold vacuum?

How much idle bypass air in the baseplate.

If you aren't using VA at idle, and no idle bypass air remove the baseplate and make sure the throttle plates are all well seated when closed with very little if any light showing around them.

A 350 build with that cam doesn't need much initial timing to be happy so don't be afraid to lower it closer to zero degrees even if you have to open up the advance curve to get the total timing where it needs to be.......

von:
Make sure the tiny choke fast idle adjustment screw on the pass side primary shaft isn't keeping the primary throttle blades open a bit when the choke is fully open.

sbc357-75camaro:
                       Thanks for your replies, all your points taken into consideration!   
      I brought the car back to my mechanic, and we pulled the cap off the distributor and had a look inside. Advance weights are sticking! They'll stick open, and stick closed, whichever way you pull them with your fingers. He sprayed a bunch of lubricant in there to loosen things up as a temporary fix, and they're much better for the time being. One of the springs is pretty weak too.
     I want to refresh the distributor and bring it back up to code. Can anyone recommend a good rebuild kit? Would one of the ones from Summit do the trick? It's a stock 1975 GM HEI distributor. Not looking for any extra performance type stuff; just looking to make if fresh again for good all around performance. Thanks for the help guys, much appreciated.

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