Cylinders 2,4,8 running rich

[llwalkman]

I am running out of ideas here. Need some help please:
65 idles
150 mains
200 air
Idle screw 1 turn out.
Idle jet holder 1.00

Cylinders 1, 3, 5, 6, 7 spark plugs are light grey
Cylinders 2, 4, 8 spark plugs are sooted black.
AFR reads at cruise ranges from 13.1- 18.5
AFR on acceleration ranges from 10.9 to 13.1
AFR at idle is 25.0 to 38.0

I know I am running lean but cannot figure out why the trailing barrel of the weber carb is running rich. Any ideas? Thanks

[Rick Parker]

1. Check for vacuum leaks, gaskets, leaks at throttle shafts and leather bearing seals.
2. Be sure the auxiliary Venturis are snug in the main body and do not wiggle, if they are loose that cannot pull emulsified fuel from the mainwell.
3. Are the cylinders similar on compression? Plugs should be light-medium brown, not grey.

[Caprimaniac]

My guess is the soot comes on when idling. Turn the idle screws on those cylinders 1/2 turn in and see what happens.

The AFR numbers looks OK, but would be 1000 times more helpful if taken from each cylinder!

[Gaz64]

Originally Posted by llwalkman

I am running out of ideas here. Need some help please:
65 idles
150 mains
200 air
Idle screw 1 turn out.
Idle jet holder 1.00

Cylinders 1, 3, 5, 6, 7 spark plugs are light grey
Cylinders 2, 4, 8 spark plugs are sooted black.
AFR reads at cruise ranges from 13.1- 18.5
AFR on acceleration ranges from 10.9 to 13.1
AFR at idle is 25.0 to 38.0

I know I am running lean but cannot figure out why the trailing barrel of the weber carb is running rich. Any ideas? Thanks

Something doesn't add up here.

Where have you got your Lambda sensor mounted?

The engine could not idle on A/F ratios of 25 - 38:1.

So the whole lot of A/F ratios could be richer than you think.

[Caprimaniac]

25- 38 is very lean; agreed. Some say that the AFR reading while idle could be a faulty read because the exhaust gasses travel at such a low speed ++. So in reality they might be lower.
And on idle the AFR can be really high, not causing any trouble.

As far as I can remember....

Will still put a coin on idle screw adjustments.

You could do a test to see WHEN the plugs soots up: at idle (fresh cleaned plugs, warm engine) and on full throat/ accellerating (again fresh cleaned plugs, warm engine)- dont' forget to turn engine off (with clutch pedal in) in the midlle of the pull...

[llwalkman]

Thanks for the response guys. Getting Closer, Inspected the floats and they were at 5.5, dropped them to 4.5 to 5.0 and the rich condition went away on the cyclinders. The soot was from test driving, I have so many sets of plugs....... the O2 sensor is right near the header flange.

I am Close, sooo close, now I am just trying to sync the left bank to the right bank. the drivers side just bounces all over the place while the passenger side is smooth. and the linkage I got from Pierce maniflods is not the best in my opinion. LArry

[Tom Howland]

Show us a picture of your linkage.

[Gaz64]

Originally Posted by llwalkman

Thanks for the response guys. Getting Closer, Inspected the floats and they were at 5.5, dropped them to 4.5 to 5.0 and the rich condition went away on the cyclinders. The soot was from test driving, I have so many sets of plugs....... the O2 sensor is right near the header flange.

I am Close, sooo close, now I am just trying to sync the left bank to the right bank. the drivers side just bounces all over the place while the passenger side is smooth. and the linkage I got from Pierce maniflods is not the best in my opinion. LArry

Second that on the linkage, get some adjustable heim joints from Dale Wilch.