Fuel System: Carter 1Barrel Carburator Question on 61 Lark VI

[Lark Novice]

Hello friends-- I am still in my 1st year of Studebaker ownership, and have a lot to learn. I have been playing with my carburator screws. One is the idle speed screw-- when I turn it in the idle speed increases-- that one I think I understand. The other screw is the air/fuel mixture screw, and I haven't mastered it yet-- When I screw it in too far the car doesn't run very well at all. My question is, what is happening when I screw that in-- is that giving me more air/less air/ more fuel/less fuel? I don't want my mixture too rich, but I also want the car to run well (duh!)

Please advise? Thanks, Martin

[christophe]

Hi Martin,

That's quite simple. The mixture screw obtures (partly) the conduit to the venturi of the carb and controls the amount of mixture. You turn the screw out to increase it and vice versa. In your case, the amount of fuel decreases. This screw is to be treated gently and must never be overtight. In fact, it never has to be tight, as the mixture is then so lean that the engine can't perform properly. You might even get a melted piston on sportier engines if the mixture is too lean.
Best of luck for your tune-up.
Nice flamingo by the way.

[gordr]

And the idle mixture screw really only affects the mixture at idle. If you have the engine badly tuned, and the idle speed screw cranked in to open the throttle well past the normal idle range, the idle mixture screw will have little effect. Best to first set the idle speed to as slow as it will go, and continue to run, tweak the idle mixture screw for smoothest/best idle, and then re-tweak idle speed screw.

Make sure your dwell and timing are correct before messing with the carb.

[Tom Bredehoft]

The air/fuel mixture screw under discussion only controls the mixture when the engine is idling. It has nothing to do with the mixture when driving down the road. To adjust, turn it in till the engine begins to stumble, back it out just enough to eliminate the stumble. If you want to play with it, slow down the idle by backing out the idle speed screw until it is just barely ticking over, then repeat the idle mixture screw, then increase the idle to where it's just smooth. with a manual transmission it should run about 400 rpm, an automatic about 700.