First days with an AEM AFR guage installed, Hmmmm.... rich at cruise? Options

[Gint]

Running pretty good. It could be leaner, but it's not horrible for a pair of carbs that sat for well over a year and a half without a rebuild. I'm getting anywhere between 12 and 13.7 to 1 when I'm getting on it. Goes a lean for a second during transition from idle to mains. I'll work that out eventually. About what I expected. Not perfect, but that was the point of installing the gauge and getting a baseline before I touched anything. The gauge does tend to fluctuate quite a bit. Even at steady state throttle/speed/grade/etc...

What's weird to my mind is that it goes stupid rich at cruise. I expected it to lean out some. Trailing throttle cruise sometimes goes as low as 10.5 briefly, usually around 11:1 though. It will go up sometimes as high as 12 at slight throttle cruise, but I expected that to be leaner as well.

Thoughts?

2.0 with about 10K on a local rebuild, 10 years ago. It's the 4 from Scott's Martini car. Stock build, pistons, cam, everything stock based on the receipt from the build. Dual Weber 40IDF's that sat for almost two years before this engine fired again this last time. I haven't rebuilt them yet. I have new jets and 32mm vents from ACE. I want to baseline what I have now, rebuild, adjust, baseline and then re-jet and check it out again. I want to see the effects of the changes as I do them.

Carbs now:
60 idles
115 mains
F11
2.0 AC
28mm Vent

[michael7810]

I have the same problem. From a small load to pedal to the metal the AF is 12.5-13.5. When at cruise with no hills it's good above 3k rpm but up to 3K the AF is 9.9-10.5. When I give it just a little more throttle it leans out to 13-ish. My numbers (by memory as I'm on travel)
60Idle; 135 main; 220 Air, 40 IDF with 32mm vents. Can't remember the other numbers. The emusion tube is "stock" according to the Weber book but I can't remember the number.

[Gint]

When at cruise with no hills it's good above 3k rpm but up to 3K the AF is 9.9-10.5. When I give it just a little more throttle it leans out to 13-ish.

I think that's primarily because as you give it more throttle it gets more air as well. I would think that would be expected. Amateur swag at best though. Again, I was just surprised to see such a fat cruise.