Hi guys, Recently rebuilt the carburettor on '80 release year buick 350 engine. Has 4 barrel quad- Unsure of specific model. It has a hot air riser for the choke. Pulling the throttle pedal, the choke plate doesn't close when cold. When warm, it does however engage in a small level depeding on whether it is a 'truely' hot engine, or just been running for a few minutes. Either way- it works sometimes on a somewhat warm engine by simply having a bit of throttle open and then the choke operates through the vaccum, or can sometimes kick in by driving away... IE.. the choke is not operating whilst cold. I feather the throttle until the engine is comfortable on it's own- then I start pulling away, and the choke suddenly operates and the car behaves as normal then on including normal kick down idle speed. At the minute I have to use my finger on the choke mechanism and I can drive away. Both the choke plate is closed, and the high idle is there. When engine is warn, the vehicle kicks down to hot idle perfectly fine and runs as it should. Although the carburettor was taken apart, I didn't bend the linkages, or change any screw settings or adjust the choke spring unit (riveted anyway). I have tried applying some lube on the linkage arms, but that hasn't done anything. I'm sure I sound like a right noob. But i've never had a car with an automatic choke, much less american iron.... All my bikes and cars currently and before have had manual chokes- Whether they are a choke with high idle, or simply in the case of my Commie German bike a 'Fuel enrichment' system which doesn't have any choke butterfly or high idle. Anyway- little stumped. Any help would be greatly appreciated!
Thank you. Unfortuantely I don't have good pictures, I do however have a video.. Just to re-iterate. Just now on the cold engine. I took the air pan off and pulled the throttle. Nothing happened. I then pushed the choke lever (?) downwards. Then, each time I pulled on the throttle linkage, the choke operated as it looks like it should. Without fail. Perhaps some more specific lubrication in the right area is required? I did put some heavy duty lub that were used for electrical contacts in phone exhanges in the 80's. I am going to try it again tonight in a few hours, If not to start it for a few seconds. And will try again tomorrow as a cold engine. Once again- I am awfully sorry for the images. But I don't get a chance in the daylight- and the car sits outside, unfortunately. My eyes aren't very good- so my focus might not be very appropriate with the images- And besides that. I can't read them myself. I believe the model is '17080248' Or is that the casting?
Interesting. The adjustment is riveted, but I suppose that if the whole assembly was taken apart the linkages are now slightly different. The only thing I don't understand is that, surely if it just needs adjustment then the starting would be consistently poor. So how come the choke sometimes come on. Just humour me here. I started the car this morning, and it's cold and damp- and the choke didn't initialise. But when I gave the throttle a slight tap after starting, it came on full..? Despite the fact that I depressed the throttle a few times before I started cranking.. I am aware the vaccum then takes over the choke? Otherwise. Thank you very much for the advice. Looks like i'll have to take the cab off again to get the drill to get to adjustment rivets...
It is binding somewhere, that is something you will have figure out as it is difficult for us to see that. I would drill those rivets out and replace them with screws. That will allow you to replace the choke coil if need be and give you some adjustability.
Okay, so I decided to take the choke coil out and clean it up. Seems to work everytime now, However- a new problem. When the choke is off fully, I found I had to adjust my idle speed somewhat. It was down 200+rpm. I made sure to put the choke position in the same place as it was. When I drive the car, pulling away, the smallest bit of gas and it sounds like it is 'dying', then jumps forwards .. I'm confused- Is it running rich or something now? EDIT, good thing I took some prior pictures, I had mixed up some tubes that go into the carb. Not sure if they make a difference? But I suppose I will find out soon.
What initial timing do you have? Are the mixture screws accessible or are the factory plugs still in place? What vacuum reading are you getting at an idle?
Everything stock. 15 degrees, mixture screws are not accessible. Other than the choke not applying when I pulled the throttle, it worked perfectly. I specifically got these two pipes mixed up, so I'll be trying it out again tomorrow..
There are hot and cold idle adjustment screw(s) on the carb. Base(hot) idle screw hits the throttle arm. The other screw hits the high(cold) idle cam, which is connected to the choke linkage.
15 degrees initial? Those mixture plugs should of been removed during the rebuild. Last time the carb was adjusted was at the factory nearly 40 years ago. You need to remove those plugs and adjust the screws to the highest vacuum reading. The Thexton #353 tool is available on Ebay.
Okay. I tried it to-day after I swapped over the pipes.. Adjusted the idle and it's perfect again. Thanks guys.. Fired up first thing this morning on choke after one press of throttle as it should. And Buick64203, I will be purchasing that tool soon to adjust the pilots. I just needed to get the car 'working' at the minute, and the only thing that wasn't working was the auto-choke. Soon I will drill those pilots out- I never liked the way the idle was so unstable and how 'rocky' the engine was.
I know this has been some time... But I thoought I'd update on my current issue. After importing the special drill bit, and adjusting tool I waited until I moved house and had a garage to keep the car in, to do anything the car needs doing to it. Plus a holiday whereby I used the car to drive to France had to be done. So I didn't do anything until recently. I have drilled out the pilot needles. Cleaned them up and them put them in exactly as they were. Installed the carburettor to the car, and now find the choke doesn't kick down! I opened up the thermostat housing, made sure it was grit free and lubricated the various levers that it activates, and gets activated from and it still won't kick down when it gets warm.. even beyond that! I've checked the choke pull off and the various vaccm lines and they test out fine. If I push it off manually, it idles nicely of course (when warm) but when i pull the throttle a bit the choke comes back 'on-line'.. activating both the high idle and closing the butterfly. I have adjusted the choke thermostat to various positions but this does nothing to stop it from activating. Any ideas ? Thank you very much in advance!
This isn't anything to do with your choke issue, but I see several vacuum lines cracked, collapsed, and not connected. This will cause many issues like stalling, erratic idle or hesitation. You really need to replace your vacuum lines. More than likely, you need a carburetor overhaul.
Hard to explain... There needs to be tension on the choke mechanism via the spring to hold the choke shut. As it warms up the spring unwinds (usually) to pull the choke open and keep it open. Tje weights on the side should drop and while running the choke pulloff shouls prevent the weights from coming back up. Is your choke electric?
Is the choke actually opening fully? Let it sit there and idle until hot. It should fully release on it's own and drop down to it's lowest idle setting.
It doesn't shift down at all. The engine gets progressively faster (obviously). As mentioned. If I push the choke mechanism off, and have the car idling at normal warm idle speed, touching the throttle will pull the choke back closed, also operating the high idle speed too. When I had the carb off the other day to drill out the pilot jets, I never touched the choke or mechanisms haha. Of course that doesn't mean I haven't disturbed anything - just nothing is obvious to me.
