I agree with Gary in that you don't want unfiltered air going into the choke assembly. All it takes is a microscopic piece of dirt to jam up the choke and render it useless.
A *properly-tuned* carburetor with a working choke should start up just as good as any *properly-functioning* EFI with a working computer. A daily driven vehicle equipped with a carburetor should only require one single pump of the pedal to set the choke on a cold start and the vehicle should immediately fire. As soon as it fires, you should be able to drive away without any hesitations or stalling in any weather condition. A warm engine doesn't even need that. A warm engine should start right up with only a turn of the key just as fast or even faster than EFI. Anything less than that and there is a problem somewhere.
The next time you start your cold engine, pull the air cleaner lid before you start to get a good view of the top of the carburetor. Push the gas pedal down once to set the choke, and then look at the carburetor to see if the choke plate closes. It should close completely and with a little bit of tension. The colder it is, the tighter that tension will be.
If that checks out, start the engine. As soon as it fires, check the choke plate again. It should crack open just a little bit and your engine should be running at a fast idle speed. As the engine warms up, the choke should gradually open all the way.
The fast idle speed should be set high enough so that the engine idles smoothly even in the coldest temperatures. Most people don't realize this, but the cold fast idle speed should be set
when the engine is at full operating temperature.This is how you do it:
With the engine fully warmed up and turned OFF, take one hand and open the throttle a little, and with your other hand pull the fast idle cam down until the "V" mark is lined up with the fast idle screw. While holding it there, release the throttle. This will hold the fast idle cam in position and "tricks" the carburetor into fast idle mode. Then, start the engine again, but DO NOT TOUCH THE GAS PEDAL. If you do, the fast idle cam will drop down and you will have to repeat the previous steps again. Now you simply turn the fast idle screw to the specified fast idle RPM. It is usually
1500 RPM or so.
This is done to to keep the fast idle speed right under different temperatures. When the temperatures are warmer, your engine will start closer to 1500 RPM and idle smoothly. When temperatures are colder, your engine will start a bit lower than 1500 RPM, but it should still idle smoothly. (You wouldn't want a very high fast idle speed on a stone cold engine in single digit weather.) In either case, you should be able to drive away immediately without any problems. As you drive the vehicle, the choke should automatically come off gradually as the engine warms up.
Just like any modern vehicle with EFI, it is actually better for your engine to drive away sooner, rather than let it sit and "warm up" or idle for a long time. Your vehicle will come up to full operating temperature faster in one mile of driving than if you let it sit at idle for 10 minutes.
The stock thermostatic air cleaner will also help the vehicle to warm up faster and provide better driveability in all weather conditions. Carbureted engines and even throttle-body fuel injection systems need a hot air source for better fuel atomization in colder conditions and to prevent carburetor icing. It is a true "cold air" intake as well, so it will also help when the weather is hot. By keeping the incoming air going into the carburetor at a somewhat consistent temperature, seasonal carburetor adjustments are often no longer needed.
Lucille: 1985 Ford F150 XLT Lariat
*Colors: Dark Canyon Red exterior, Canyon Red interior
*Engine: 5.0, CompCams 31-230-3, "Thumper" E7 heads, Edelbrock Performer intake, Autolite 4100 carburetor, DuraSpark II ignition, Thorley Tri-Y headers, Flowmaster dual exhaust, H-pipe.
*Drivetrain: AOD transmission, 3.55 gears, 2wd.
Locked
