carb adjustment help....
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Senior User
Joined: Apr 2001
Posts: 285
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From: Houston
carb adjustment help....
Well, to catch everyone up on my problem, my truck (74 460 engine) won't hold idle. It used to idle just fine at 650 rpms. Now anything below 900 and it will die. So when I'm at a red light, I have to hold the gas to 900 rpm or it will surge down to 450 then down to 250 and die. I bought a motorcraft rebuild kit for my carb and it has an instruction sheet in it w/ all of the adjustments needed for the carb to operate smoothly. So I thought untill I have time to take the carb off, I will just adjust the idle up to 900 rpms. The instructions showed two screws on the bottom front of the carb and said they were the idle screws. I turned these screws till they were all the way in and nothing. NOTHING CHANGED! I unscrewed them 5 complete turns and nothing changed. What does this mean? Does this point out a specific problem that I should look for when I do a rebuild? I tried looking at the carb on my 68 cougar that is out of a 84 mustang but they are completely different.
Any thoughts?
Austin
Any thoughts?
Austin
Mountain Pass
Joined: Nov 2001
Posts: 153
Likes: 0
From: Caldwell, KS
carb adjustment help....
those screws arn't for adjusting the idle speed, rather they adjust the idle mixture. They adjust the air/fuel mixture at idle only, the adjustment for the idle speed will be o the side of the carb were the linkage connects to the pedal, you should be able to figure out which one it is easily, it will cause the linkage to move slightley to a mopre open or closed position. As far as you idle mixture screws, now that you have moved them you will have to go back to a base line adjustment. Turn them until they lightly seat (bottom out softley) thren back them out 1 1/2 turns that should get you by until you can rebuild the carb, But I wouldn't wait to long to do that, depending on what condition your motor is running, such as too lean, it could damage your motor if you don't get it corrected.
Thread Starter
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Senior User
Joined: Apr 2001
Posts: 285
Likes: 0
From: Houston
carb adjustment help....
I set the screws back to stock setings. Thanks for the help. I turned the idle up to 900 rpm and now once it warms up, it only takes one foot to drive instead of two. No more holding the gas at a red light. I still need to rebuild it because something has to be wrong for it to not be able to hold the same idle it used to.
Thanks
Austin
Thanks
Austin
