Car Won't Idle After Carburetor Replacement

[Richin65]

Hi Guys.....Need some thoughts here.

Just placed a carburetor (4682s) on my 68 383. Once it fires up, I have to keep the foot on the accelerator and the idle speed up on it. When I do that, the engine will run, but a little rough. Once I take my foot off the accelerator, it dies instantly. The carb is a rebuilt by a reputable mechanic, so I feel pretty confident with that, but you never know I guess.  Also, anything I do with the adjustments doesn't seem to make a difference. The car was running decent before I swapped off the carbs (I removed the old carb as it will need a rebuilt).

Appreciate your inputs.

[XH29N0G]

Others will know more, but have you checked to make sure you don't have a large vacuum leak.  PCV hooked up, etc.....  I would check to see if the choke was working because I assume it is also cold.  What is the lowest RPM it will run?

[Richin65]

Others will know more, but have you checked to make sure you don't have a large vacuum leak.  PCV hooked up, etc.....  I would check to see if the choke was working because I assume it is also cold.  What is the lowest RPM it will run?

Not sure about the RPM. Pretty low and it will start to stall out. Car was cold, but let it warm up, and made no difference. My suspicions are a vacuum leak as well, although everything is hooked up correctly. Appreciate your thoughts!!!!

[XH29N0G]

I would just make sure it doesn't keep running at something like 750 -850 RPM.  Or if maybe you can keep it running a little higher then you can find if you have a vacuum leak.  Mine did that a few weeks ago when I forgot to connect the PCV tube. 

Unfortunately I am not the one to diagnose this so hopefully someone else will pipe in.

[myk]

You said "carbs."  What engine and setup are we talking about?

As was said earlier, check all hoses, lines, etc.  Make sure the 'carb to intake gasket is on properly as well...

[BLK 68 R/T]

I know you said it was rebuilt but if everything else checks out ok, ie: vacuum leaks, fuel filter not plugged. It's possible the floats are set incorrectly. With the floats set incorrectly the fuel level will be either way to high, forcing more gas into the engine at idle than it can take which is why you have to increase the rpm, to burn the extra gas. Or with the float level set to low, you are having to increase the rpm to pull gas from the secondary circuit instead of the engine being able to run on the idle circuit.

[Dino]

If it was shipped to you after the rebuild then definitely check the floats.  Just remove the carb, open it up and check everything out.  You never know what got in it. 

[Richin65]

Thank you for the inputs. Still frustrated......Put the old carb back on, replaced the base gasket, and still getting the same problem with old carb back on it (which ran okay before I initially removed it), so don't think the new carb was the problem. I'm baffled on this one.....

[XH29N0G]

Do you have a stock intake?  Does the manifold have any vacuum fittings?

[Richin65]

Do you have a stock intake?  Does the manifold have any vacuum fittings?

Just noticed that the vacuum advance line was off.....duhhh....running again.  Thanks!!!

[XH29N0G]

Excellent news. 

[myk]

Lol.  That's like when I can't find my keys and they're either in my pocket or in the ignition of something.  Congrats 'OP!

[ws23rt]

  This is the kind of fix we all hope for.

[Richin65]

Thanks guys!!