I've been having problems starting up my '76 L48, and my father in law suggested holding open the choke and trying to start it. Sure enough, this worked just fine. When i would tap the gas, the choke would slightly close, to a maximum of about 75% closed. I let the car sit overnight, and this morning, the choke was still wide open. I believe that it is supposed to close when the engine is cold, correct?

The choke blade should close completely when the temp is cold. Once started, the vacuum pull-off should open it slightly, to keep from flooding. Then, as the engine temp warms, the choke should go to full open automatically.
You may have a broken/damaged spring inside the choke housing.
Is this the original Quadrapuke, or an aftermarket carb? Does it have an electical connection on the choke housing?Adams' Apple2007-01-23 07:07:08

As far ask i know, it i s an original carb....it doesn't look like it's an aftermarket carb. It hasn't given me any problems until the past week or so. Could it be that it is gummed up (for lack of a better term)? It moves freely when manipulated by hand.

What about installing a manual choke????

[QUOTE=IR1976]... It moves freely when manipulated by hand.[/QUOTE]

It should have some tension on it at all times, either holding it open, or holding it closed.
With the engine cold, you should be able to step on the accelerator pedal slightly, and the choke should close.

As Joel has said sort of.... the correct way to start is to pump your pedal ONCE.  This will reset the choke to closed, and also pump a small amount of fuel into the manifold.  When you crank it over and it fires, the vacuum system will open the choke slightly so the engine doesn't get too much fuel and not enough air.  As the engine heats up the choke should open according to the temp of the engine (that's for auto chokes only). Chips582007-01-23 16:24:57

[QUOTE=IR1976]As far ask i know, it i s an original carb....it doesn't look like it's an aftermarket carb. It hasn't given me any problems until the past week or so. Could it be that it is gummed up (for lack of a better term)? It moves freely when manipulated by hand.[/QUOTE]

by any chance did you clean outside of carb with something like gumout spray? have noticed when i used it sometimes linkage would stick.  gumout would dry everything up that linkage couldn't move freely. a real small amount of wd 40 or a silicone lubricant did the trick. just a thought.

I haven't cleaned it with anything. It seems that when i press on the gas when the engine is cold, the choke will close. However, it seems to want to stutter and then sometimes stall out when the choke is closes. Granted, it's like 25 degrees in my garage, and this might have something to do with it....

IF you had some sort of vapors coming out of the carb, it could mean a timing problem, or there is something else wrong with the carb. It could also just be some leftover fuel in the intake that spat out when one of the intake valves opened.
Might be time for carb surgery...

Yep, I agree with Joel.  If it's a Quadrapuke just go and buy a 600 Holley.  You'll never have a problem with it.  While you're at it why not throw an Edelbrock performer manifold on to go with the Holley.  You WILL notice the difference.