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From Another C3 Forum:

"I just bought a 1979 L82, manual transmission, all original with 35k miles. I made all the preliminary adjustments, installed a new steel fuel line since the original had been kinked. I filled the bowl and she started right up on fast idle, ran a couple minutes till the choke got hot and fell down to slow idle. At slow idle it's very rich. I've turned the mixture screws in to the point that it's barely idling but it's still eye watering rich. Somewhere I'm getting a lot of extra fuel at an idle and I'm not sure where. This one has me stumped".


The mixture screws on QuadraJets add air when opened; not fuel. Same with the Rochesters as their mixture screws also add air when opened. When mixture screws are located in the base plate they add air when opened.

Holleys on the other hand have their mixture screws located high up in the sides of their metering blocks and they add fuel when opened; not air. That's why Holley mixture screws have a neoprene seal around them to prevent their sucking in air and leaning the mixture.

So I'm guessing this gentleman is simply turning his QuadraJet's mixture screws the wrong way while thinking he's choking off the fuel when he's actually choking off the air; making it run very rich. The mixture screws on QuadrJats are usually opened 2-3/4 to 3 turns.
 
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