I have a Holley Street Avenger Carburetors 575 carb on a non-modified 292. The car would always idle fast. I checked the secondaries and found they would not close all way. I adjusted the stop they still won't close. i shined a lite through it and saw light. The vacuum secondary pull rod is extended all the way down. Any ideas  how to over this. 

Richard (Buz) Mills
Dallas, TX

First, the idle speed is supposed to be controlled by the secondary butterflies.  There is an idle slot that needs at least .015"-.020" showing.  That means the secondaries will be slightly open.  If you closed them down and opened up the primary side, you have taken away the adjustability that is designed into almost all Holley carbs.  Joe-JDC

JDC

OK.. That makes sense. I can set the set screw for the secondaries back to where it was. I made sure to note how many turns I did. That's all i did. However when i gently closed the idle adjustments it will still idle. The idle jet tips are good. No bends, burs, etc. Internal seat looks good too.

If "idle adjustments" is the idle mixture screws and the engine still runs with those turned in, then some possibilities are primary throttle opened too far (this relates to what Joe said), float level too high, bad needle and seat, sunk float, too much fuel pressure, blown power valve, bad power valve gasket.


Lawrenceville, GA

You should be looking at the Primary Throttle plate Position. Take the Carb off.Turn it over and adjust Idle Speed Screw so that the Idle transfer Slots or just small Squares below the Throttle Plate. Make a note of how far the Screw needs to be turned from contact with throttle Lever to get Transfer Slots Square( for future reference if needed). In that Position the Engine should quit as Idle Mix Screws are turned inwards.Start there and see how Idle is. Do not open Primary Throttle Plates any further than where they are Set initially. Use Secondary Throttle Plate Screw to adjust Idle Speed if required,.The Secondary Plates need to be open slightly to draw a little fuel from Secondary Fuel Bowl so Fuel stays fresh. OR You may just simply have a Vacuum Leak?

  

One of the causes of this condition on Holley carburetors is the carb gasket is not allowing the linkage to seat consistently.  This can drive you nuts.  If you turn the carb upside down, you will notice part of the linkage hangs down slightly below the base.  Some Holley gaskets are too wide in this area.  The fix is to cut a small slot out of the gasket.

You don’t mention if you had purchased this carburetor new or used.  If used, then the possibility exists that someone previously has had the secondary throttle blades loosened or removed from the shaft and did not get them aligned properly when retightened.  A worst case scenario is if the blades have been completely removed and one or both were put back on upside down.  Check that the angled chamfer at the edge of both the blades do fit flat to the bores when the shafts are in the fully closed position.   If you have backed off the secondary idle adjustment screw to the point that it has an air gap and you still see light coming past the closed secondary throttle blades, then it does sound like a misalignment or other blade issue when the blades were tightened to the shaft.  In cases such as these, one blade will typically be showing more light than the other.
 
The other thing that comes to mind on the Holley 4V carbs in general is the secondary spring being changed out or modified to the point that it does not have the tension to keep the secondary blades seated in the closed position.

Lorena, Texas (South of Waco)

simler problem,my cure was close the secondary so ther was just a small opening,way more than the holley book recommended, next made sure the exhaust flapper was working. put slight increase in jet size in primary,the rest was  minor fidling of idea screws,  this was a new holley 6000 on a 292 in my 49 merc f47.  it runs great no backfires ,secondarys com in  for a great performer. i do have a dist. converted to ford duraspark ign.. run lots of advance,use the whit wire on the module when cranking(that retards the timing)only on start.