A very good explanation of Weber carbs.

Texasroadrunner

Club Member
I found that one a year ago and read it several times. Very informative and it helped me tune my DCOE 40's. I was able to get rid of the annoying 1,800 rpm bog without making the plugs black.
My favorite chart was "The Ideal Relationship of the Three Fuel Delivery Circuits" and the color Idle jet diagrams below it. I have two O2 sensors. One on cylinders 1-3 and the other on cylinders 4-6.
The dual AFR gauge on my console has helped me get the carbs responding well and the spark plugs a nice tan color with a clean and happy powerband.

Texasroadrunner
 

SeanDezart

Well-Known Forum User
I have two O2 sensors. One on cylinders 1-3 and the other on cylinders 4-6.
The dual AFR gauge on my console has helped me get the carbs responding well and the spark plugs a nice tan color with a clean and happy powerband.

Would you say that is much more effective than a single sensor at the junction of all 6x primary pipes ?
 

Texasroadrunner

Club Member
He Sean, I do enjoy seeing the AFR numbers change while I'm adjusting the idle mixture screws on Weber DCOE's. Having two O2 sensors makes setting them more accurate since I make all 3 needles (cyls 1-3) the same turns out. Then
I set the other 3 needles (cyls 4-6). If it was all six cylinders read by a single O2 sensor, it would be more difficult. The best info from the AFR gauges with Weber carbs is during the transition zone from idle circuit to Main, taken care of by the Idle jets. The AFR is very
sensitive to different idle jet sizes. After an idle or main jet change and a long test lap, I pull a few spark plugs to verify what I was seeing on the gauges and how the engine responds. This method takes much of the mystery out of tuning. When the AFR reads too
lean as in 17:1 there will always be a bog. Someplace between 13:1 and 14:1 is the sweet spot for power and good gas mileage.
 
have your factory got a car they can line it up on? Are there any s30's in china? Or if there are, are they being imported by 'new money' there? might be a growing market?
 

SeanDezart

Well-Known Forum User
...plenty on here but luckily, I know what I'm doing, have ramps and a selection of early to late S30s upon which to experiment.
 
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