so i have a autolite 2100 in my 67 289 with really high idle so i went to adjust the idle using the screw located next to the throttle assembly but turning the screw doesnt do anything it doesnt come into contact with the plate under it as it should be! how should i fix this?

 

this is because your choke butterfly is closed. the plate on top of the carb.
if you check the linkage on choke butterfly on other side of carb it will lead to a swivel to wich you have another stop screw. that's the fast idle screw. this casues the car to run quicker (higher rpm) when it's cold.
So you can only adjuts curb idle (your screw) until the car is warm, choke butterfly fully open and the fast idle screw on the other side of carb not interfering

 

also check that little diaphram just to the left of your circle that the throttle closes against. If it's frozen in the extended position it will also keep the idle screw from making contact and cause a high idle.

 

that might be it as well, just wanted to point out that you absolutely cannot adjust curb idle with choke butterfly closed

 

And make sure you have no vacuum leaks.

 

Hi,
I am the tech manager at Autolite and a 1967 mustang owner as well. You should get a rebuild kit for your carb and go through it. They rebuild kit is very inexpensive and the 2100 is one of the easiest carbs ever made to rebuild. The instructions in the kit will explain adjusting the choke, the idle mixture, fast idle and idle speed. Its an easy project.
Good luck