Re: Holley 4160 idles with mixture screws threaded all the way in
Exactly which carb is it? 4160 isn't helpful. Look on the front of the choke housing inside the air filter area, should have something like this, LIST-1850, with possibly -1, -2, -3, etc.
Now, some Holley's are emissions calibrated replacement carbs, and work with dead stock engines ONLY, even a K&N air filter element messes them up. Those emissions carbs also use a reverse idle system, fixed jet size, always too lean, and, will run better when the air screws are turned all the way in.
Post the LIST number, and we can go from there with it.