Odd carb question

[ChrisDollins]

I've been DDing my 66 for a few months and it hasn't missed a beat until last week. It started missing pretty bad under load and seemed to be flooded at idle. Like fuel smoke sitting in the drive-thru at sonic. So I adjusted the carb this morning to see if it would help. Now, the truck has been running great for the last 2 years, so its odd it just started. Anyway, I turned the mixture screw in all the way and it cleared up and ran better. I backed it back out either a 1/4 or half a turn because i was expecting it to stall all the way in. Could something have gone bad in the carb, or what do you think?

Chris

Btw, the engine still spits and sputters at shut off for a couple of seconds and seems to run backwards...
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[R_W]

What type of carb?
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[ChrisDollins]

Crap, can't believe i forgot that lol. Factory single barrel on 250.

Chris
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[Wrenchbender Ret]

You probably have a bad float that is getting gas in the pontoons.

[ChrisDollins]

Thanks for the response. Would that beable to be adjusted out? The truck runs and idles as good as it ever has. It's just the screw is almost bottomed out.

Chris
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[Rufton]

If the idle screw lost function I think it's time for a rebuild kit. Maybe fuel shut off valve (included in kit) is leaking. Ret's pontoons may be a little low like he said so be sure and check em during rebuild.

[cortcomp]

If you turn the screw in and it's still running, it's getting the fuel from somewhere, so either bad internal gasket/leak somehow, or like wrench said, bad float or something letting it get fuel in that way. Those are an easy/cheap carb to rebuild, give it a try and it will likely work out for you...use carb cleaner spray with the little red tube nozzles and compressed air to make sure those passages are nice and clean.

[geezer#99]

If the mixture screw changes nothing then the throttle (idle speed) is too high.
Turn the idle down. If it's too low then make sure your vac pot on the distributor is hooked up. Vac adavance will increase your idle so you can turn the idle back down with the idle speed screw.
Then your mixture screw should respond.

[Rufton]

Originally Posted by geezer#99

If the mixture screw changes nothing then the throttle (idle speed) is too high.
Turn the idle down. If it's too low then make sure your vac pot on the distributor is hooked up. Vac adavance will increase your idle so you can turn the idle back down with the idle speed screw.
Then your mixture screw should respond.

Good point!

I'd pull a plug after hot idle. If off white then may be as simple as geezer said.
If black then may be bowl overflowing as others mentioned.

[TJ's Chevy]

Sometime those old carbs can crack and cuase a vacuum leak. My factory 1 barrel had the same issue, though it was not cracked theres a vacuum leak in it some were and it has been rebuilt several times.

[ChrisDollins]

Thanks again guys. I'm new to the carb world. I think its just time for a rebuilt carb. I did raise the idle some when this first started and it seemed to help. Then replaced plugs and wires (they were black). Then problem has been getting progressively worse quick. So as a last resort adjusted the screw. The last couple of days it has ran perfect with the screw a 1/4 turn out from bottom. Will get a replacement soon before it strands me.

Chris
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[ChrisDollins]

Vacuum port is hooked up, and I lowered the idle back down to normal before I adjusted it. It was just getting dumped with fuel.

Chris
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