i dont do it that way. hook a vacume gauge to a source of constant vacume, of the carb or intake. start with the screws about 1.5 turns out each, and set the idle where the truck will run smoothly. then turning each screw 1/4 turn at a time look at the gauge. as you turn it in or out the vaccume will drop and rise slightly. when you get it to the highest point of vaccume, play with the other screw the same way. youll notice the vaccume will only get so high before it flat lines. you want it as close to the high point without going into the flat line as you can get. the 2 screws may or may not be exactly equal, at this point i will leave them alone if they are close to the same, if not one goes in slightly and one comes out to split the difference. then set the idle to what ever idle speed you prefer. my car with an auto was adjusted this way, and will idle at 500rpm in gear with the air on without stumbling. the highest point of manifold vaccume gives you the best idle power, alowing a lower idle speed without stumbling. i also set the timing this way as well. not saying its the best, just the way i was taught and may work better then what was posted before. call it plan b....lol

btw, if you continue to turn the idle screws out the engine speed will continue to climb, you are adding fuel, there will be no threshold where it quits, you will just be running real rich with an incredibly high idle. out of all the 1,2,and 4bbls i have ever adjusted, if your out more then approx 2 full turns, something else is wrong. most set between 1 and 1.5 turns.



Edited 1 time(s). Last edit at 04/24/2009 10:46PM by wideblock.