At My Wits End With This Choke!

[savatreatabvr]

I installed a manual choke on my mid 70's 454 Quadrajet, when I have the choke on it fires right up and idles but runs really rough. As soon as I take the choke off and feather the throttle to get it to idle it runs good and even better when warmed up! Do I need to adjust the choke flap to open more when the choke is on? I'm thinking the flap is closed to much so it's not getting enough air. Make any since?

[tucsonjwt]

Caution: Long Post Ahead
I have an 83 C20 454 with a manual choke and have had manual chokes on all of my squares. You need to adjust the choke when the engine is stone cold - first thing in the morning. Adjust the choke so that the choke valve is just completely closed with the engine cold - don't go beyond the full closure setting or the cable will bind up in the sleeve and be under pressure. You should hold the throttle lever back so that the choke valve will close all the way when you are doing the adjustment. Even on a hot day your choke valve should be closed completely prior to start up.
Before you start the engine, remove the air cleaner and verify that the choke is fully closed. Press the accelerator all the way to the floor while pulling the choke knob all the way out - remove your foot completely from the accelerator while still keeping pressure on the choke knob - this insures that the choke valve closes all the way. (If you have not driven your truck for a few days you may need to pump the accelerator a few times to put gas in the carburetor before you start this process.)
After driving the truck for a few minutes you should stop, remove the air cleaner, and verify that the choke valve is all the way open - straight up and down vertical position. If not completely open, then adjust the choke until it is just all the way open. I have heard 454s called "cold blooded", meaning that they need choking a bit longer than a small block while they warm up. I experienced this in cold climates, but not here in southern AZ.
I have my choke cable adjusted so that the choke knob sticks out about 1/4" away from the knob bracket when completely open - that way I know for sure when the choke is all the way open - if the choke knob bottoms out on the bracket I know that the cable has become loose somewhere under the hood - this happened to me a few times, requiring readjustment of the cable.
Don't give up on the manual choke. When adjusted properly (which is so simple even I can do it) it is the best choke you can get. You may have other problems with your carburetor but the choke issue is easy to troubleshoot and fix and at least then you can eliminate it from the problem equation.

[savatreatabvr]

I'm wondering during the installation of my manual choke if I could have messed up the lever assembly linkage thingys, lol, and they need to be set again, I'm kinda dumbfounded when it comes to that stuff? My father had an old 59 Chevy with a manual choke and it worked perfectly, so I'm determined to this figure out, I think I need to step back and take a deep breath!

Originally Posted by tucsonjwt

Caution: Long Post Ahead
I have an 83 C20 454 with a manual choke and have had manual chokes on all of my squares. You need to adjust the choke when the engine is stone cold - first thing in the morning. Adjust the choke so that the choke valve is just completely closed with the engine cold - don't go beyond the full closure setting or the cable will bind up in the sleeve and be under pressure. You should hold the throttle lever back so that the choke valve will close all the way when you are doing the adjustment. Even on a hot day your choke valve should be closed completely prior to start up.
Before you start the engine, remove the air cleaner and verify that the choke is fully closed. Press the accelerator all the way to the floor while pulling the choke knob all the way out - remove your foot completely from the accelerator while still keeping pressure on the choke knob - this insures that the choke valve closes all the way. (If you have not driven your truck for a few days you may need to pump the accelerator a few times to put gas in the carburetor before you start this process.)
After driving the truck for a few minutes you should stop, remove the air cleaner, and verify that the choke valve is all the way open - straight up and down vertical position. If not completely open, then adjust the choke until it is just all the way open. I have heard 454s called "cold blooded", meaning that they need choking a bit longer than a small block while they warm up. I experienced this in cold climates, but not here in southern AZ.
I have my choke cable adjusted so that the choke knob sticks out about 1/4" away from the knob bracket when completely open - that way I know for sure when the choke is all the way open - if the choke knob bottoms out on the bracket I know that the cable has become loose somewhere under the hood - this happened to me a few times, requiring readjustment of the cable.
Don't give up on the manual choke. When adjusted properly (which is so simple even I can do it) it is the best choke you can get. You may have other problems with your carburetor but the choke issue is easy to troubleshoot and fix and at least then you can eliminate it from the problem equation.

[tucsonjwt]

Not likely. The only thing you should have touched is the choke housing - replacing the thermostatic choke coil cover with the manual choke cover. There is nothing on that right side of the carburetor to get messed up. Just make sure you pull back on the throttle bracket on the left side of the carburetor when you do the adjustment (this is really depressing your accelerator all the way as described above.) By pulling the throttle bracket back all the way you are releasing a cam below it which holds the choke valve back and prevents it from closing all the way.
I know nothing about carburetors but I know a fair amount about manual chokes, having installed a few. I suggest you follow the procedure I described in the previous post and see how that goes. I am pretty sure you just need to adjust that manual choke properly and you will be good to go - not saying that you don't have other carburetor problems, but the choke should not be one of them. If all else fails, don't let anybody talk you out of your Qjet - a good rebuilt Qjet beats all of the aftermarket carbs I have owned - just get a top notch carb rebuilder and you will be satisfied with it.

[savatreatabvr]

It didn't have a choke housing to begin with, I'm assuming you're talking about the round choke housing? So I just hooked the cable to something that moved the choke flap open and closed and called it good, but of course it's not good, lol!

Originally Posted by tucsonjwt

Not likely. The only thing you should have touched is the choke housing - replacing the thermostatic choke coil cover with the manual choke cover. There is nothing on that right side of the carburetor to get messed up. Just make sure you pull back on the throttle bracket on the left side of the carburetor when you do the adjustment (this is really depressing your accelerator all the way as described above.) By pulling the throttle bracket back all the way you are releasing a cam below it which holds the choke valve back and prevents it from closing all the way.
I know nothing about carburetors but I know a fair amount about manual chokes, having installed a few. I suggest you follow the procedure I described in the previous post and see how that goes. I am pretty sure you just need to adjust that manual choke properly and you will be good to go - not saying that you don't have other carburetor problems, but the choke should not be one of them. If all else fails, don't let anybody talk you out of your Qjet - a good rebuilt Qjet beats all of the aftermarket carbs I have owned - just get a top notch carb rebuilder and you will be satisfied with it.

[Bad Karma]

Looks like you're missing some pieces... Is that an "in progress" pic, or is that how you're running it?

[cjlinkster]

Originally Posted by savatreatabvr

I installed a manual choke on my mid 70's 454 Quadrajet, when I have the choke on it fires right up and idles but runs really rough. As soon as I take the choke off and feather the throttle to get it to idle it runs good and even better when warmed up! Do I need to adjust the choke flap to open more when the choke is on? I'm thinking the flap is closed to much so it's not getting enough air. Make any since?

It sounds like you are really close to having it work correctly. If your carb doesn't have the front choke pull-off (or it if doesn't work), the purpose of the pull-off is to open the choke plate roughly 1/4" upon imediantly starting the engine.

With your manual choke, you may need to mimic the same action. Upon the engine starting, relax the choke a little for 2~3 minutes and then gradually opening it up.

Did you ever replace the thermostat? Is the enigine warming up correctly??

[donut]

Maybe a mod could merge your choke threads?

Sound like your close, does the fast idle work? I believe I had to hold the throttle open a little, then set the choke, this would allow the fast idle cam to engage. Then start it.

Fully closed my choke still had about a 1/4" gap from being sealed.
How does it run at partial choke?

[savatreatabvr]

That's what I'm wondering, am I missing pieces? Yes, it runs with the current set up!

Originally Posted by Bad Karma

Looks like you're missing some pieces... Is that an "in progress" pic, or is that how you're running it?

[savatreatabvr]

Choke pull-off? What's a choke pull-off? Since you said it's supposed to be roughly 1/4" open I need to adjust it because it's less than that. It does take 10+ minutes running and driving before it idles normal. I'll replace the thermostat but what temp should I get for the mild Phoenix winters?

Originally Posted by cjlinkster

It sounds like you are really close to having it work correctly. If your carb doesn't have the front choke pull-off (or it if doesn't work), the purpose of the pull-off is to open the choke plate roughly 1/4" upon imediantly starting the engine.

With your manual choke, you may need to mimic the same action. Upon the engine starting, relax the choke a little for 2~3 minutes and then gradually opening it up.

Did you ever replace the thermostat? Is the enigine warming up correctly??

[donut]

Thermostat, personally I'd go with whatever is recommended. My '73 was a 195 degree.

As long as the rest of the cooling system is up to snuff, it's not to high. Your engine actually needs heat to help burn the nasties out of the engine oil, pcv system will then remove them. I lived in Mesa and Tempe during my younger years, so I do know the summer heat and mild winters.

I saw the pic posted, if I were to bet, I'd say it's a divorced choke carb. If it was complete, you'd have a raised pad on the intake and a thermostatic spring on it, and a small rod going from the spring to the linkage your current cable is attached to. If you do a site search, I believe I saw some pics of that setup in the 67-72 section.

Choke pull-off, I believe is the vacuum can in the pic, front of carb, attached to choke linkage. (I don't see it, but there should be a linkage connecting it to the rest of the choke assembly)

On mine what I did, I found a small sheetmetal "L" piece, big enough to go from the end of the choke blade and down enough to clear the aircleaner. Tackwelded it on to the end of the choke blade, small hole to attach cable and clear everything. This would operate the blade, and everything else was run on it's own linkage. Because I essentially installed it backwards, operation was backwards. Bracket was enough to clear the carb body, and drop it enough to clear the air cleaner. I sold the truck about 4 mos ago, so I can't snap a picture. I'm also in a part of the country that isn't wired for high speed internet, so looking for links doesn't quite work for me. (I'm NOT paying the $$$ for satellite.)