I am currently running a DCOE 48 carb on a stockport 12A with full RB Streetport exhaust and direct-fire ignition. Here are my jetting specs.

40mm Venturis
45F6 Idle jets
210 main jets
F9 emulsion tubes
160 air corrector

Let me start off by saying that the car runs and drives and that I've already put about 2500 miles on it since I bought it. I recently installed an innovate lc1 wideband and xd1 guage and am reading ~12.2:1 at idle (it won't idle well at all if its any leaner, I've tried adjusting it already). Under cruise I am anywhere from 10.0:1 up to 11.3:1. Part throttle is around 13.0:1 and full throttle is ~11.2:1 and drops to 10.2:1 by redline.

I know that the F6 idle jets are really rich (my numbers prove that). I'm thinking of going with 55F9 as a starting point. As for the main circuit, I'll worry about that later, I'm just sick of 12MPG so I want to redo the idle jets (I do alot of highway).

Does anybody have a better suggestion for me for idle jets or are 55F9s good? I also want to switch over to 38mm venturies if that would make a difference in the idle jet that I would need.

Thanks guys

 

Since no one answered, I'll try. I would buy 2-3 sizes of idle jets and try leanest first and see how driveability is, and if your mpg increases. In other words run the leanest jet that you can with decent driveability. I'm not sure how this will effect your idle quality.
Most of us are running the F11 tubes. FYI in my 12a large streetport race motor I'm running F11's, 185 mains, 145 a/c. ALso with the large idle jets. It's rich as a pig at idle but MPG is irrelevant, and I'm always above 5000 rpm anyway. WIth this jetting I'm seeing egt's of 1500-1600. I wish I had a wideband like you do.

ALso Robert (rotaryshack.com) is the best at jetting of anyone on this forum. Send him an email. He can help. Good luck.