AFR tuning

[Norris McCarty]

I’ve a 40 coupe with a 53 Merc that has a Max1 cam, Navarro heads, 3x2 Navarro intake with 2 real 97 Strombergs setup to run together(much better than running the 3 progressive) and Reds headers. I’m also running one of Charlie’s SBC mechcanical advance distributors. This engine has about 2000 mile and runs good.
I can’t leave well enough alone, so I installed an Innovate AFR gauge in the glovebox.
I’ve just started tuning.
With both carbs set perfectly with a vacuum gauge it idles with an AFR of 12.7.
I understand that a perfect idle should be 14.7 on the gauge, but if I close the mixture screws in enough to lean out the mixture to around 14 on the gauge, it doesn’t idle near as good. Does this mean that I have a problem somewhere? Perhaps a vacuum leak? The car idles beautifully at 680 rpm.
As I get into cruise tuning I’ll report back.
Just curious....I know most would just not worry about it.