stock 1973 318 V8 starts but won't idle without foot on pedal

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Put a vacuum gauge on it. I bet it's low because it has a vacuum leak. Rough or no idle is classic symptom.
 
A vacuum leak is my #1 possibility. I tried spraying quick start all around the edge of the intake manifold and the carburetor base but did not get a real reaction anywhere. I am also inexperienced at this test and I don't really know what is supposed to happen if there is a vacuum leak. Maybe a positive reaction is more subtle than I was looking for.
 
Lasalle said:
A vacuum leak is my #1 possibility. I tried spraying quick start all around the edge of the intake manifold and the carburetor base but did not get a real reaction anywhere. I am also inexperienced at this test and I don't really know what is supposed to happen if there is a vacuum leak. Maybe a positive reaction is more subtle than I was looking for.
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If you have a vacuum leak, any combustible will make the engine race. The leak will suck in the vapors and the idle will change. You can also do it with a un-lit propane torch.
 
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toolmanmike, did you mean to say "any" combustible will make the engine race?
 
Bewy said:
If the car has been in storage for 25 yrs, might have sediment blocking the idle system.
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25 years of crap and shellac in the small orifices.
Lean, not because of vac leak, but no fuel.
Pull the idle screws out and hose the screw holes with carb cleaner. If that doesn’t do it, rebuild the carb.

Damn, it’s been setting 25 years!
Gas prolly smells like varnish. And probably is.
 
I finally solved the problem! I had the carburetor rebuilt and then I adjusted the mixture screws properly and it idles like it should now. This is the short version of the story. I have been stumped by this all summer. In the end I learned there is no substitute for doing the research and learning how to do it yourself. Professionals do not even have enough help to work on modern cars these days much less put time in on the old ones. Thanks to all who responded!
 
Lasalle said:
I finally solved the problem! I had the carburetor rebuilt and then I adjusted the mixture screws properly and it idles like it should now. This is the short version of the story. I have been stumped by this all summer. In the end I learned there is no substitute for doing the research and learning how to do it yourself. Professionals do not even have enough help to work on modern cars these days much less put time in on the old ones. Thanks to all who responded!
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I was going to suggest a complete tear down and clean to remove fine dirt particles... but glad you got your problem taken care of.
 
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