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Old 08-13-2010, 12:40 PM
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Q-jet running too rich

Quick question: I have a 750 q jet on my chevy 350 and it seems to be running kinda rich. I'm eventually going to get it tuned but in the mean time i need to solve one problem. When the car is idling it starts sounding like it's getting flooded and if i don't give it some throttle it will eventually die. This causes a problem because it doesn't want to start for a while afterwards and i don't wan to be stuck in a parking lot or gas station because of this. Any thoughts on what i can do to solve this until i get it tuned?

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Old 08-13-2010, 01:44 PM
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It could be a number of things. The needle might be sticking in the seat in the up position and floding the carb. Try taping it lightly and see if it improves. Another cause is the plugs at the base of the carb leaking. You will need to pull the carb and check them. If it was running good before than I would not suspect incorrect rods and jets. If it has sat for a long time it could be the needle. Also check the fuel pressure. It should be around 5 psi. And make sure you have a filter in the carb. Without one the fuel pressure increases and can cause flooding. Final one I can think of is incorrect float level.
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Old 08-13-2010, 01:55 PM
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i think the carb came off a bigger engine and was never tuned for the 350. what about the 2 screws on the front?
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Old 08-13-2010, 02:06 PM
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If the vehicle takes a lot of cranking- as if the carb were dry- after it has sat overnight or longer, the main wells could be leaking. This is a common Q-jet problem. It will cause the idle to be too rich as well.

By all means adjust the idle mixture screws! They often have odd-shaped heads, so you might need to remove them and cut a screwdriver slot into them so you can easily adjust them- if you don't have the correct carb tool to use.

If you do this, before removing the screws, count the number of turns until they lightly bottom. Write these numbers down- you won't remember them.

Then after cutting the slots, bottom the screws lightly again then back them out the same number of turns that you counted before removing them.

Then w/the engine warmed up to operating temperature, connect a diagnostic vacuum gage to a manifold vacuum port and adjust the screws to give the highest vacuum reading.

You want the screws to be very close to the same number of turns out. You should be able to keep them within 1/4 but not more than 1/2 turn apart.
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Old 08-13-2010, 04:19 PM
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Alright, thanks for the help. I'll play with it and see if it gets any better.
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