WHO SAYS I NEED A CHOKE?
Lots of people run without a choke and that is fine, after all no one can tell you how to set up your engine. If you bump up the idle rpm your engine will run fine before it is warmed up. If you do this, the engine RPM will rise after the engine warms up. The choke isn't just for the weather changes, it is more for the engine temperature. Many people say that since I only drive in the summer, or my seasonal temperature changes aren't too large, I don't need a choke. That's not really the right way to think about it. Keep reading to see why.
WHAT DOES A CHOKE DO?
A choke restricts the incoming air into a carburetor so that there will be excess fuel available to richen the air-fuel ratio to help the engine start. Gasoline has to be a vapor to ignite, and with higher temperatures, it will change from a liquid into a vapor easier. That means that gasoline is more difficult to burn when it is colder. This can be due to the weather being colder, but an engine is always colder than operating temperature if it hasn't been running in a few hours.
Either way you look at it, the choke compensates for temperature changes.
IF YOU DON'T LIKE CHOKES.... DO YOU NOT LIKE THERMOSTATS EITHER?
If you like thermostats, you should like chokes. The thermostat opens after the engine warms up because your engine runs best at a certain temperature. If you ran your engine temperature too high, you won't be driving too much longer. The thermostat keeps the engine cool after the engine is warmed up. The choke helps the engine to burn fuel until it is warmed up...
Not using the choke won't do any damage, and because the choke only gets used for a few minutes when you start a cold engine, it doesn't really get all that much respect.
Not using the choke won't do any damage, and because the choke only gets used for a few minutes when you start a cold engine, it doesn't really get all that much respect.
WHAT IS YOUR SEASONAL TEMPERATURE RANGE?
It's typical to live in an area where the summer temperature is 100° F and the winter temperature is 0° F. That is a seasonal temperature change of 100° F, right?
WHAT IS YOUR ENGINE TEMPERATURE RANGE?
This can get as complicated as you want to make it. The good thing is that it doesn't have to be. To keep everything simple, a conservative estimate of a combustion chamber is 250° F. We are not talking about your coolant temperature, exhaust, or the engine bay temperature. Since you are burning fuel in your engine, the air-to-fuel ratio INSIDE the combustion chamber is important, and 250° F is a decent estimate. It's probably a good deal higher than that, but we are keeping it simple.
Now think about your engine. A "cold" engine will have the same temperature as the air around it. That would be 100° F in the summer and 0° F in the winter.
It's about 250° F inside your engine. In reality, it's probably higher than that, but remember we are keeping it simple.
So in the summer, the temperature difference from a cold engine to a warm engine is 100° F compared to 250° F.
It's about 250° F inside your engine. In reality, it's probably higher than that, but remember we are keeping it simple.
So in the summer, the temperature difference from a cold engine to a warm engine is 100° F compared to 250° F.
250° F - 100° F = 150° F Difference in Summer
In the winter, the temperature difference from a cold engine to a warm engine is 0° F compared to 250° F.
250° F - 0° F = 250° F Difference in Winter
WHAT'S YOUR POINT?
The point is that the temperature difference from a cold engine to a fully warmed up engine is larger than seasonal temperature differences. That is why I say the choke is for the engine temperature changes instead of seasonal weather temperature changes.
A CHOKE ISN'T FOR SEASONAL WEATHER CHANGES - IT IS FOR ENGINE TEMPERATURE CHANGES
Of course a choke is more useful in the winter if the weather is very cold, because the outside air temperature is a lot lower than where the engine temperature should be when it is warmed up, so the difference in the engine is more noticeable. If a carburetor is setup to run without a choke and runs well, it means that the temperature difference is being compensated for somewhere else in the tuning of the carburetor. If you are okay with that, good.
UNLESS YOU LIVE WHERE THE OUTDOOR TEMPERATURE IS 250° F, A CHOKE WILL HELP YOU
If the outdoor temperature and the engine operating temperature were the same, no one would have trouble starting any type of engine and chokes wouldn't exist because there wouldn't be any point. I don't think this applies to anyone, and If I was somewhere that was 250° F the last thing on my mind would be a choke.
I DON'T KNOW HOW TO SET THE CHOKE
You're not alone. That's why most people don't use them. Tuning a carburetor can be frustrating, and if you are having trouble just getting it tuned right, adjusting an electric choke just adds another headache. Most of the time, I find that people don't use their choke because they don't know how to set it up. It's a lot easier than tuning...
The Edelbrock Carburetor Owner's Manual has all the information you would ever need, and it's actually written well. Unfortunately, it's written well like a textbook, and since textbooks are boring, nobody actually wants to read it. The instructions for adjusting the choke aren't too long and there are pictures.
WANT AN EASIER EXPLANATION?
Start with a cold engine and take off your air cleaner. Start the engine and make sure the choke plate is CLOSED. You will want to do this quickly because you need the engine to be cold and the choke operating to adjust the choked idle RPM. Read your tach and adjust the choke fast idle screw to the RPM that you want the cold, choked engine to idle at. To gain access to the choke idle screw, you will probably have to turn the engine off to gain access. If you don't know what I am talking about, try to adjust that choke fast idle screw with the engine running and you will understand. You can buy yourself some more time by turning the choke cap as far clockwise as you can. What this does is increase the amount of time that they choke will stay closed. You still have to do this quickly because otherwise you are adjusting the choke on a choked engine that has already warmed up. The choke will start opening as it gets warmer. You can gently push the choke plate closed with your finger to give yourself more time. If you run out of time and the engine is warmed up, you will have to let the engine cool down and start over.
After you have the choke fast idle adjusted to the correct RPM, with a manual choke, you are now done. The electric choke works automatically and can be set for different lengths of time, so if you have an electric choke you can adjust this. Start your engine and let it warm up to operating temperature. When the engine is completely warmed up, turn the choke cap counter-clockwise until the plate starts to move. Turn it back clockwise one click. Tighten up the three choke cap screws TIGHTLY and you're done.
After you have the choke fast idle adjusted to the correct RPM, with a manual choke, you are now done. The electric choke works automatically and can be set for different lengths of time, so if you have an electric choke you can adjust this. Start your engine and let it warm up to operating temperature. When the engine is completely warmed up, turn the choke cap counter-clockwise until the plate starts to move. Turn it back clockwise one click. Tighten up the three choke cap screws TIGHTLY and you're done.
SET IT AND FORGET IT - I WANT TO CONVERT MY MANUAL CHOKE TO ELECTRIC
If you have a Performer Series manual choke carburetor (1404, 1405, 1407, and 1412) you can use the Electric Choke Conversion Kit which is part 1478. Click the link below for the install instructions.
Edelbrock 1478 Electric Choke Conversion Kit
The 1478 kit does not work on Thunder Series carburetors.
Edelbrock 1478 Electric Choke Conversion Kit
The 1478 kit does not work on Thunder Series carburetors.
I STILL DON'T WANT TO USE THE CHOKE
Everybody has their reasons. The good thing is that you don't have to remove all the parts. If you remove all the choke parts, you could create a vacuum leak, so it's better to just leave the parts in place and disable it.
DISABLE A MANUAL CHOKE
If you have a manual choke, just leave it open. Don't touch it. It's a manual choke, so since the driver is in charge of opening and closing the choke.... just don't ever close it. Done.
DISABLE AN ELECTRIC CHOKE
There are a couple of things that you can do. The first one would be to rotate the choke housing counter-clockwise enough so that the even if the choke does close, it will not be closed long. The second thing that you can do is adjust the fast idle linkage so that even when the choke wants to work, it is adjusted so that it will not affect your idle speed.
Once you have made the adjustments, make sure that the choke is fully opened all the time. You can do this by starting the engine when the engine is cold with the air cleaner off. The choke flap will not move at all and will be in the same position whether the engine is off and cold, or warm and running. If you are not using a choke, your idle RPM will still rise anyway... because the engine will be running more efficiently after it is warmed up. (Or the RPMs will be lower than were the idle RPM is set until the engine is warmed up.)
Once you have made the adjustments, make sure that the choke is fully opened all the time. You can do this by starting the engine when the engine is cold with the air cleaner off. The choke flap will not move at all and will be in the same position whether the engine is off and cold, or warm and running. If you are not using a choke, your idle RPM will still rise anyway... because the engine will be running more efficiently after it is warmed up. (Or the RPMs will be lower than were the idle RPM is set until the engine is warmed up.)
WHAT'S YOUR PROBLEM? WHY DO YOU CARE ABOUT CHOKES SO MUCH?
I mess around with lopey cams. The downside to having a rolling idle is that it can be harder to have a smooth idle at lower RPMs. Most people just compensate by jacking up the idle RPM higher to smooth it out. You don't have to do that. If you have a lopey cam, letting the choke do it's job allows you to get a smoother idle at a lower RPM even if the engine is cold. What's wrong with a smoother idle at a lower RPM?