Need Carb Jet Guidance, Weber 40 IDFs Options

[bbrock]

Plans to Megasquirt my car got delayed over the winter so my Webers will stay on for another summer. So, I finally hooked up my wideband to see if any adjustments are needed to keep the engine happy and safe until I can do the conversion.

The only real "problem" area is idle and low speed driving on the progression circuit where it is running too rich. It idles smooth and steady at 700 rpm with AFR of 12.3. That with idle mix screws ~ 2 turns off their seats. That's the leanest I can adjust and keep the engine happy. Just off idle at 20-40 mph @3000 rpm it goes even more rich to around 11.0 +/- 0.5. I don't think that's alarmingly rich but wasteful and I do get a bit of annoying surging/bucking driving below 30 mph.

Current jetting is as follows:

Venturi - 28
Emulsion tubes - F11
Main jet - 115
Correction Jet - 200
Idle jet - 50

I'm thinking I should reduce the idle jet but not sure by how much. I can get .047, .045, or .040. Any suggestions?

I could also use some advice on mains and/or air correction jets. If I didn't plan to swap the carbs to FI, I'd try for a little leaner highway cruising mix for better economy and maybe flexibility. In limited testing running in good ranges for performance at the expense of economy - WOT ~12.5, Highway cruise ~13.5 but rarely goes above 14.0 even on downhill and decel. Weather is crappy here this weekend so I've only done a short drive in hilly conditions. I need to get it down in the valley for some long level runs to see where it settles. I think I can live with the numbers I'm seeing now, but do wonder what it will do when I attempt to cross a 10,000 ft. pass. I'd rather it not die of oxygen starvation if I attempt it. Any thoughts?

BTW, I live at 6,000 ft. elevation so I'm not surprised it is running on the rich side with out of the box jetting.

[930cabman]

I have been following this to a certain degree as I am a carb guy and currently wrestling with a hex (hexed) bar linkage setup.

Couple things:

It's possible the technology of the Webers will never provide the information with regards to A/F numbers

Did you mention the car is running good? Maybe leave well enough alone until you can convert to an FI system

From what I know the idle speed screw needs to be about 3/4 turn max from initial contact. Also the mixture screws should be around 1 1/2" turns our from the seated position.

[bbrock]

Did you mention the car is running good? Maybe leave well enough alone until you can convert to an FI system

Depends on how we define "running good." If it means being able to drive like a bat out of hell and feel a strong pull all the way to 90, then it is dialed in to the nines. If we add fuel economy to the equation, it is not running good at all. The mileage sucks and I'm lucky to get 200 miles out of a tank of gas. I got closer to 400 miles when it ran on the long in the tooth DJet. I have a long trip I'd like to take it on the end of this month, but won't if I have to stop every 200 miles to fill it with liquid gold.

New jets are already paid for and on their way so should be able to do something to improve economy. Honestly, I never expected out of the box stock jetting to be ideal at 6,000 ft. so none of this surprises me.