Thanks. That's where they were. It didn't even have the caps on it. I hadn't paid any attention to that hole because it's so small. Interesting thing is that when I started, I had 16" of vacuum. I turned those screws in until the engine started to stumble and back out until it stumbled on the other end. There was very little vacuum variation. Problem? (I'm drawing my vacuum off the Offy intake.) I set both carbs to the middle point between those points.

There are 3 places to draw vacuum; two on the carb and on in the center of the intake. There are two points about a third of the way up from the bottom on each carb. The other is at the very base of the carb. Where should I draw vacuum to adjust the carb? Where should I draw vacuum to drive the vacuum advance?

Jerry Acheson
Indianapolis, IN
57 Chevy 3100