A/F Graph Interpretation (Help Needed)

[cwestra]

Looking for someone who can help diagnose some A/F data I recorded recently on my 340 6-barrel Cuda.  The graphs are for various speed and acceleration conditions.

Float level, idle speed, timing, are set correctly.  A/F sensor is calibrated.

I started with the idle screws on the outboard carbs fully closed and adjusted the center idle screws to max. smoothness (2-1/4 turns).  I then ran the outboards to 3/8 turn (starting point).  Idle was okay and showed slightly lean on A/F meter but driving was rough and lacked performance and at cruise I was extremely lean.  In increments of 1/8 turn for outboard idle screws (leaving centers alone) I eventually settled on 5/8.  At this setting the idle showed rich (around 11.5 to 12.5) but idled nicely and transitioned well at a cruise.  It was still, however, showing somewhat lean as the speed went up, which is a concern for me.  I'm not sure where to go from here.  Adjusting the idle screws out further to correct for a lean condition at cruise doesn't seem logical. 

Under hard acceleration I see a different A/F pattern in 1st gear than the other 3 gears, for some reason.  Through 1st I go from rich to lean, while in the other gears I go from lean to rich.  Not sure why.

Should I be looking at raising the float level in outboard or center carbs to address it, without further richening the idle circuit?
Should I change jet size in center carb (currently 61's)?
Should I change powervalve (currently 6.5)?
Will a spring change in outboard vacuum pods work?

Any help would be appreciated.

[cudabob496]

I'd research the web. Adjusting 3 two barrels to optimize AFR throughout the rpm range seems like almost
an impossible task.  I have an AFR meter on my 496, and have just tuned the carb to get a WOT AFR of about 12.5.
It would be a lot easier if you had fuel injection.

It does look like you have it dialed in quite well for the hard acceleration runs, where your AFR seems to be around the desired
12.5 to 13 range.

From what I've read, you would never want to be above 14.7.


http://www.enginebuildermag.com/Item/15762/carburetor_tuning_the_airfuel_equation.aspx

http://www.circletrack.com/enginetech/ctrp_0404_jetting_carburetors/viewall.html

[Chryco Psycho]

inserting a small diameter wire into the jet circuit air bleeds may correct the lean criuse condition
 Maybe in 1st gear the rpm rises quickly enough to fully open the outboard carbs fully very quickly whille in the higher gears ithe ported vacuum rises more slowly not fully opening the carbs as fast .
I agree that using the mixture screws to richen or adjust cruise or WOT is the wrong way .
 Using a 4.5 pwoervalve may help the rich condition during transistion but should still be open @ WOT either way , changing the springs may help as well but opening them faster may cause it to stumble , you can change 1 spring at a time as the seconadries open with combined spring pressure so using 1 lighter spring is a 1/2 step change