|UPDATED|9/14/2014 8:35:25 AM (AZT)|/UPDATED|

Check for a vacuum leak...it would be a fairly large leak for it to not idle. It would cause it to run rough like that, as well as spit back thru the carb.
Does it have any black smoke from the tailpipes?
Do you smell raw/excessive fuel?
It's possible the float is stuck in the carb, and the engine is flooding with too much fuel. Tapping on the fuel inlet on the carb will usually un-stick a float, depending on what might be causing it to hang.
Also possible the points are burnt, or out of adjustment. Cap/rotor problems.
So many thing could cause it. Just gotta start with the basics. Vacuum leak? Too much fuel? Spark issue?
Eliminate one at a time.

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Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Joel, I did check the distributor: Cap, rotor and ignition points look fine and clean (except for a little bit of red dust in the cap and the rotor. No grease, no carbon trace. I also checked the ignition coil: I get 6V at the (+) and at the center connector tha goes to the distributor. 6V is kind of a surprise but I get the same in and out. The vacuum: Where should I start to check a leack? I do not understand the role of the vacuum in the carburation. Obviously there is as I got an excess of gasoline driping on the ground just aft of the front left wheel. I believe it came from the canister. The vacuum system usually needs several minutes to build up vacuum enough to lift the headlights. I wish I could keep the engine running long enough to see that. Not sure where to start from to find a leak (I didn't here any particular noise of this kind). Christian

Disconnect the vacuum line at the white filter and plug it.  Then see how it idles.

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Just did it. No change. Still running rough and not holding idle.

This points to the carb flooding. It sounds like fuel is overflowing into the vent tube on the front of the carb, and running down into the canister. See if you can pinch off the fuel line going TO the fuel pump, effectively shutting off the fuel supply to the carb. Start it up, and once running again, it will use the excess fuel, and then run ok for a few minutes, until it runs out of fuel. Sometimes doing this will also flush out any debris that might be stuck in the needle/seat of the carb, if that is what is causing the flooding.


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Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thank you Joel,

 Hope it's something simple.

Years ago, when I was taking the '74 to it's 1st NCRS Judging in Waco, we were to meet up with some other folks on the road. I was driving the car down(for driving points), and trailering it back home.We got to the meeting spot, and I realized I had forgotten to bring the lug nuts for the steel rims, which I was going to change to from the aluminuminum rims once we got there. I hop in the car and haul butt back to the house for the lug nuts. As I exited the hiway, the car wouldn't stay running...it was flooding out big-time. I made it to the house, got the nuts, and limped back to the meeting spot. Once there, I had to take the top off the carb, took the float out, and had someone crank the engine(with the coil wire off), and flushed some crap out of the needle/seat. Took about 10 minutes....car has run fine ever since. Was running fine before, too...just something made it past the filters, and lodged in the needle/seat. Ya never know when it could happen, but you can bet it will usually be at the worst possible time...



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Joel Adams
C3VR Lifetime Member #56    
My Link


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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Joel,




|UPDATED|9/20/2014 11:56:06 AM (AZT)|/UPDATED|

Now I am even more puzzled!!!!!

|UPDATED|9/20/2014 11:55:21 AM (AZT)|/UPDATED|

 Two things could be happening, from your description. The fuel pump may be able to provide decent volume, but what about pressure?It's possible that when clamping off the return line, you raised the pressure enough to keep the bowl full. The problem MAY be a stuck float still....if it is hanging, the extra pressure from the return line being clamped off could force the fuel on thru. The problem could also be the fuel pump itself.
Do you have a way to check the fuel pressure?

To get the accelerator linkage lever off the carb top, there is a TINY roll pin that goes thru it....take a small punch, or nail, and press the roll pin inward, toward the carb body. This will allow you to remove the linkage, and the top of the carb. When re-assembling it, you can use a small screwdriver to pry the roll pin back into the linkage lever.

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Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

No, I don't. How would you do that?


Thanks. I saw it, but I didn't dare to remove it because I was not sure I can insert it back in place, correctly.

You would need a fuel pressure gauge,and connect it after the fuel pump. You could remove the fuel line going into the carb, and connect it there. You'll be looking for at least 6psi under heavy throttle.

The roll pin, when pushed IN, will not go anywhere...it will bottom out against the carb choke housing...so it will not fall out, and get lost.





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Joel Adams
C3VR Lifetime Member #56    
My Link


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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thank you very much for the tip.