I need your guys help.

Just picked up a nice clean 81 F250 with a 300 6 cylinder, manual tranny and that goofy tiny little Carter, made for Motorcraft carb on it.

I need to know the turns settings on all three screws, because before I got it and now, it will NOT idle. It runs fine to drive it, sort of, but dies when you let off the throttle to shift. Starts right back up, thats no problem but this carb is driving me nuts!

HELP!

 

I had that motor in one of my pickups ( a '69 F 100),but it had big one barrel Ford or Motorcraft carb on it...one mixture screw,one idle speed screw,and a damned automatic choke which I converted to manual choke.Sounds like the idle speed screw or the cam on the auto choke is your problem.You can tinker with it to try and get it working right,but often times the parts that interlink the choke plate to the throttle mechanism and idle cam just wear out.You may be best advised to search ebay,or a parts yard for a new/better carb,unles you're inclined to take the carb of and work on it on your bench...that 300/six is a GREAT motor ( seven main bearings!)

 

The engine must be warmed and choke blade in the full open (vertical ) position? If yes, then you might do the following;
Make sure there are no vacuum leaks, hoses off or broken. If so correct that.
If you bottom the idle mixture screw lightly, bring it out about 2 turns.
Then turn in the idle speed screw in enough to keep the engine running.
Slowly back out the idle speed screw like a half turn at a time, then
If you try turning the mixture screw in or out you should notice a change in engine speed. Find the setting that gives you the fastest idle speed and set it there.
Now go back, and back the idle speed screw out a little more to lower that idle speed to around 600 RPM in neutral. Again adjust the mixture screw to obtain best idle speed. That should get you in the ball park.
I gather you are not that familiar with the adjustments and that is where fine tuning the carb comes in. You really should use a tach to set the correct idle speed. It could be in the area of 600-900 RPM , I would need to verify the recommended setting.
Setting the fast idle isn't difficult , but you need to get it to idle correctly first. Let us know how you make out , then we can do the fast idle setting . OK ?