OK. Can someone please tell me which one does what. I think my idle is running a little too fast and i'd like to lower it - I know the two screws adjust that, but I want to make sure I do it right. Please explain in left screw/right screw terms - thanks. Oh yeah, I did do a site-search first but found nothing giving idiot-proof instructions!
OK Ill try to do as you ask ...THE idle screw is NOT the two on the front of the carb they are for adjusting the mixture ( richer or leaner) turning them clockwise is to lean the mixture OK NOW ifyou want to increase the idle that screw is always on the drivers side and mounted on the throttle lever LOOK around it is sometimes hidden but it is there hope that helps pete
With the engine fully warmed up [that is important] gently turn one of the idle mixture screws [ the ones in the front of the carb] in untill the engine begins to run rough and the rpm s drop. back out untill it smoothes out and stop. do that for each idle mixture screw. then go to the idle speed screw on the side of the carb and raise or lower it untill you get the desired rpm.
Those two mixture screws end up to be almost 1 turn each for me.......(just for a starting point for you). Set the idle speed with the screw on the far left side by the throttle shaft to set the idle speed after doing the other 2 first. Then check one more time, b/c a change in idle speed can affect the idle mixture a tiny bit.
Isn't there a larger screw in between the idle mixture screws that is used to set idle speed on a Carter AFB (aluminum four barrel)? I seem to remember one on my '67 Pontiac Catalina.
Yes.......the rear carb on the DQ setup is like that. The center screw is for setting the idle speed. When you screw it in, the speed goes down. It's actually an air screw, so when you screw it out it allows more air to go in thereby increasing the idle speed. The idle speed screw on the throttle shaft is non-existant on this carb, which is to the best of my knowledge only used with factory dual carbs.
Actually, I had one of those Carters with the air bleed screw in the center of the carb. I took it off a 57 merc [turnpike cruiser] with a 383 engine. [ no it was not a Pontiac engine, Merc had a 383 back in the 50's.] I put it on a 57 ford daily driver. When the engine is running the carb has a awesome sucking sound as the air goes in the carb. This sound freaks people out when you pull up to a red light. They think that the car has a huffer on it. this was my favorite carter carb. i have often wished that I had another one. They were on 57-58 Lincolns and Mercs that had the 430 and 383 engines. [the 430 was the Lincoln engine] Along about this time I was working for a ford dealer in pasadena Tex. One day a guy came in the service dept with a 57 ford 2 door that had the 383 merc engine in it that had come from the factory that way. we traced the serial numbers and confirmed the factory build. Now, at that time supposedly you could only get up to a 312 cu. engine in a ford. It had the Carter carb with the big brass center air bleed screw in it. The car was built in 1957 [late] , and this was 1962. The service rep at ford said ''by the way that car is still in warrenty''!!!!! Some kind of factory exp. deal. I watched the road test after the tune up and the car would absolutely fry the back tires.
