General engine question

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Silent Thunder

Silent Thunder

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A general engine question, I have a 64 273 V-8 non comando engine with a 4 barrel 600cfm edlebrock carburetor automatic choke. When the car is cold it idles fine, 750 rpm, when it warms up it is at 550 rpm when the needle passed the middle a little bit and the engine is fully warmed up and its say 85 degrees out the idle drops even further, 200-250 rpm and eventually drops so low it shuts off. Now I know the easy answer is adjust the idle on the carb but when I increase it for the hottest times then on the cold its 1400 rpms. My question is: Is there anything that can effect the idle speed on an engine besides the carburetor? If something is worn can it make the idle drop when warm? I want to rule everything out but the carborater. If that it all it could be I will re focus on that. I have gone to two seperate mechanics who work on carb engines (they are over 50 years old) and they have each adjusted it with the same results.
 
maybe the choke isn't opening all the way and it's flooding out. I had the same problem believe it or not with the same carb. I would be sitting at a stop light or in traffic and the car would just start to idle slower and slower till it would stop. I had to keep pumping the gas to keep it going, but with a 4 speed, thats a lot of pedal work. I adjusted the choke a little, bumped the idle just a touch and it seems to have gone away. Try the choke if your mechanic buddies have not.
Maybe the timing could be bumped a little.
Just my thoughts..
 
A vacuum leak can do that too. I had a problem like that in a older OT truck and the issue was the carb needing a rebuild and a new dizzy since the advance weights were hanging.
 
Could have some "junk" in the jets from your lines.
 
Probably a stupid question here, but which screw are you using to set idle? There should be one for idle and one for high idle on the choke cam.

From your description it sounds as if you are using the choke idle screw.
 
The electric choke housing is adjustable. The black plastic housing turns adjusting the rpm setting. Look in the instruction booklet and it will explain. Is the vaccuum port for the advance (if any on the right port )
 
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