Going lean when shifting...

Guys,

I have an AFR gauge on my car. LA 360, with Edelbrock 600 CFM, manual choke (1405).

When I'm gently accelerating up to speed, the AFRs go way lean from 1st to 2nd, and 2nd to 3rd.

I've been searching the internet to try to UNDERSTAND WHY this happens. And to try to determine how to prevent it, or read some advice on how to prevent it.

Generally it doesn't stumble when it does this, except before the engine is fully warmed up.

I haven't fully finished tuning it in, as I'm currently working on making my own metering jets. Once I have the Power Mode and Cruise Mode AFR's where I want them, then I'll get serious about this issue.

Does anyone understand this? Or have you read about this somewhere you could link me to? What I find sort of kind of just skims the surface of this.

I don't have much of a theory, but I wonder if the metering rods may be dropping into their jets during a shift (from the power step to the cruise step) and starves it of gas for a second. Dunno. I don't know what happens to the vacuum during a shift. If the vacuum spikes during a shift, I guess it would suck the metering rods down before kind of returning to where they were. Kind of makes me want to increase the length of my custom power step further up (toward the L) on my metering rods. Maybe then it won't switch from power to cruise (if this is what is happening).


7milesout