arem04667

I just recently bought a 85 camaro with a "rebuilt" 4bbl 750 cfm carb. The guy i bought it from said it had just been rebuilt, but i didnt ask if he did it himself or if a shop did it. Something is wrong with it. The choke butterfly stays open all the time, doesnt close, and the secondary butterfly doesnt open at all. I'm thinking something broke, but ive never dealt with a carb before so i dont even know, and have no idea where to look.
The car has been running fine, i actually didnt notice there was a problem until yesterday when i took the air cleaner off.
Any help would be greatly appreciated.

b1lk1

Choke butterflies should operate when the car is cold, but the secondary butterflies are not likely to open much when you are not putting the engine under load.

lowridetractor

iTrader: (2)

sounds like a vacuum secondary carb.
the secondaries won't open till there is a load on the engine. as b1lk1 stated
what kind of catb is it? holley edelbrock q-jet?
is the choke hooked up?
can you post a pic?

arem04667

Sorry, I ve been busy and havent been able to get back on here.
Its a quadrajet carb. I compared the old carb the guy i bought it from gave me, to the one that is on right now, it appears that the choke butterfly isnt connected to anything.

correct me if im wrong, but, a working choke stays closed when starting the car, and as temperature increases it opens up?

DoubleV

Pretty much. Here's a quick explanation on how the choke works;

When you go to start a cold car, the choke is open because it was open the last time you drove it ( assuming you let it warm up of course ). This is why you pump the gas pedal when you try and start the car...it 'sets the choke' aka allows the choke to snap shut. You only need to pump the gas once to set the choke. The choke should be all the way shut or darn close to it when it's 'set'. The reason for the choke being shut is to give a very rich mixture to the engine when cranking.

After the engine starts, the vacuum diaphram on the carb now cracks the choke open a little bit so it's not as rich as when you were cranking the engine over ( but still richer than normal ). The amount it opens is adjustable by the screw on the diaphram. Just adjust it for best drivability.

As the car warms up, the choke opens up more untill it's all the way open. When you shut the car off and let it cool down completly, the choke will still be open as I mentioned above, requiring you to pump the gas pedal ( thus setting the choke ) to start the cold car. And the cycle continues....

It's really quite simple. I wish somebody would have taken the 2 minutes to explain this all to me when I was younger and hadn't a clue. I went years without fully understanding exactly how it all worked!

arem04667

Well, now it looks like the choke is working properly. funny thing was i didnt do anything to it. im thinking maybe it was just stuck when i looked at it before. i sprayed it down with some carb cleaner just incase.

it does seem to struggle to stay running when it first starts, the previous owner said the choke might need to be adjusted a bit, but im not sure how to adjust it.

DoubleV

As mentioned above, to adjust how far the choke opens after the car starts you just turn the screw on the front vacuum diaphram. Adjust it untill your car runs good when cold. Choke should only be open a small amount.

Probably one of the easiest things you could fiddle with on a carb other than adjusting the idle.

spawnicus

so what would cause the butterfly to be stuck open?, fully open?, mine is, i cant even shut it by hand

five7kid

iTrader: (14)

As I said in your thread, hold the throttle open a little bit and see if you can move the choke thermostat.

DoubleV

Maybe the linkage is messed up? It's hard to say without seeing it.

Take the choke over off ( round black plastic part on passenger side of carb with a wire going to it ). This is where the choke spring is located. See what happens when you remove that.