Well, I have brand new Edelbrock 4 barrel carb. #1813S 4077. It is a copy of the Carter AVS. It's the weekend, so I can't call Edelbrock.

Anyway, the driver side mixture screw offers zero change to the engine idle when I adjust it. I even took it all the way out, and nothing happened. The passenger side mixture makes changes when I adjust it, and the engine idles and runs terrific. The throttle blades are definitely in the correct relation to the transfer slots. I poked a needle in the hole with the mixture screw out and it didn't feel plugged. The metering rod looks fine too.

Even though it runs great, I'm curious as to why I can't get any adjustment out of it.