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I have a '78 F-150 with a 302 with this carb. (see attached) Can anyone help with the basic settings for the two adjustment screws in the front? Or any other
adjustments as starting points?
the standard start point is to screw them all the way in then back out 2 1/2 turns. then at a warm idle open them up until you hear the engine slow down, then back in until it slows down again and that's where your setting is . if you don't hear the engine slow as you back them out then just go in until it does. you can use a vacuum gauge to set it even closer but it's not needed.
To add to what sixpack said. I always consider carb adjustments kind of a dance (like distributor points dwell/gap adjustment) where once you've fiddled with the mixture screws, you then have to re-set the main idle speed screw (sometimes). And once you do that, you might have to re-set the mixture screws to their "new best setting" because things have changed with throttle blade position.
So don't hesitate to do these adjustments two, three or even more times if that's what it takes to get the best balance.
And the two screws do NOT need to be at exactly the same setting. It's all about what makes the engine idle the best. If one ends up being 2 turns and the other 2 3/4 turns, that's what it takes with your particular carburetor.
Don't turn the mixture screws in too tight. Just gently bottom them out because the tips and the carb casting are slightly delicate and can deform. Changing yet again how much adjustment they might need.
With no experience, it can be very difficult to tune a carb properly. Luckily, there is a cheap tool out there that takes a lot of the guess work out of the equation.
A Vacuum Gauge. Using one, and tuning for the highest reading achieveable is the way to do it.
To set a baseline, I like to pull the carb, get a rebuild kit with all the settings for the particular carb, then clean, rebuild and bench set everything. There's some linkage adjustments that most people never do, but it's really simple, that really effect how well the carb works. Most OEM or reman carbs I've ever done were slightly out of spec somewhere. Every time I've done it, it's improved start up and gave it a much crisper throttle. Making sure the choke is free and adjusted correctly is also important.
Regarding the choke adjustment, following the procedure described in this link will ensure that your choke linkage is synced and adjusted perfectly. It always works for me. Good luck!! https://www.ford-trucks.com/forums/7...ml#post6422219
