When the engine is cold, it can use the extra fuel your carb is dribbling into the engine, same as the choke being closed or nearly so.
How about the fuel pump? How old is it? A weak fuel pump can lead to a low float level, and the problem can come and go. I remember that from the 72 Skylark 350-2, that was my first Buick. Does your fuel pump have a vapor return line? If so, is it hooked up and functional?
Fuel pump was on the car when I got it a couple years ago. It does have a return that as far as I know is working. I wouldn't be surprised if it was the original pump. I also read on a different forum about a vent on top of the carb sticking shut and causing similar issues. I'm going to check that out tomorrow, assuming it doesn't rain all day again.
If you can, and its not raining on you, take pics or a vid with the air cleaner housing off of the carb and the car fully warmed up (after driving for awhile) and idling.
That vent was stuck. now it's unstuck, but i couldn't see it actually doing anything once the car was warmed up. the problem did seem lessened, but not cured. Now it has to be in gear and sitting at a light for the idle to get bad. i took a little video of it idling. I'm aware i have an exhaust leak. I'm also aware of how mickey mouse that **** on the fuel line is.
I'm not sure what vent you are referring to. The main vent on that carburetor is right there inside the throttle bore up top. Unless someone stuck something inside of it, it would always be open to the atmosphere. One thing I noticed from your video, the choke vacuum break appears to be defective. With the engine running, vacuum should pull the link all the way in. Yours is extended. That means the diaphragm is defective. That could potentially create a small vacuum leak.
Suddenly this is not a high priority anymore. My th350 is about to die. Full of fluid but slipping and dropping out of third. Anybody got a line on a 200-4r for cheap?
Going to be some work to convert that 2 barrel to accept a 200r4 tv cable. And you will really want a deeper 3 series rear gear or it will load up under 45 in overdrive.
If you end up doing the tranny swap feel free to pick my brain. I had to fabricate a tv cable mount on my 2 barrel 300 before I did the motor swap.
If you're hurting for funds and need the car to be street worthy, about the cheapest transmission you're going to find would be a solid non-switch pitch ST300 (there's a few board members here who want to get rid of theirs, last I heard). You can get those for practically free since everyone needs their car to jolt the fillings out of their teeth with 4.10 gears and a 200-4r trans (which won't be cheap any way you slice it). It'll bolt right up in a direct swap, no fuss.
Know I'm late to your post. Did you solve your warm starting issue? When you experience extra cranking to start when it is warm, does it seem to fire better if you let off the key from start to run? You should try it and see. If my speculation is correct, you may have a bad starter. How old is it? Even if it works, it can be bad. What happens is when you engage the starter, it draws a lot of current from the battery to spin the engine. If the starter is bad, it can starve your ignition system. GM designed the ignition system to run on about 5 to 5.5 volts in normal operation (running) to prolong the life of the points. That is why there is resistance wire going to the coil. However, for starting, there is wire from the solenoid to the coil (typically yellow) that provides 12 volts to the coil for starting. If the starter is drawing down the voltage excessively, the coil can actually not have enough voltage to start the car. I would replace the starter and solenoid and your warm starting problem should be resolved. I experienced this first hand on my corvette. As far as your carb is concerned, if you have a foam float, replace it with a metal one. The foam floats are notorious for losing buoyancy over time. Set the float level and adjust the mixture using a vacuum gauge.
Don't want to add insult to injury, but being your having issues with your carb and such, and now your trans. is shot, why complicate matters further by swapping in a 2004R trans? The 4 speed auto WILL need a rear gear change from (probably 2.56 gear) to a 3.42/3.73 gear plus the TV cable set up. If the Throttle Valve cable is not proper, it WILL fry the 2004R trans in short order. Get your T350 trans rebuilt, then re-address the carb issue
I know its an old thread, but I wanted to come back and post what solved the problem. Carb was indeed shot and leaking down the intake, put a remanufactured one on and the problem went away.
