After adjusting the valves and checking the timing, I checked carb sync - The 3 barrels on the left side (Driver side USA) all read 4, while the 3 cylinders on the right are 5 or 6. Is this a linkage issue, or should I just adjust idle air to increase or decrease?

Thanks in advance!

Topic has attachments Syncing Webers from Aug 11th

Never synch'd 4 cylinder Webers, but many many times with 6 cyl IDAs. About 4 on the synchrometer with small bore 6's. I do it the very old way learned from an old Weber manual... lost the hardcover book but author's name begins with a P!
Step 1 is disconnect L and R carb banks.
Screw in all idle air adjustment screws all the way in.
Run engine about 900 RPM
Get L and R banks close using idle adjustment screws
Do initial tune with idle mixture screws, enough to run all cylinders
Synch within each bank.
Start at the lowest synch reading cylinder and open idle air screw until match with highest synch reading cylinder.
Move to opposite bank and repeat.
Make sure idle stays sround 900 RPM
Adjust idle mixture screws
Adjust L to R throttle rods, leave one side loose, and attach both
That gets L to R close
Now, because of throttle linkage slop, you have to further adust the loose side running angine at about 2000 RPM.
Use synch to adjust and match both banks at 2000 RPM
Tighten everything down and rechech synch at both 900 and 2000 RPM

Idle air adjustment will likely remain the same for a while. The idle mixture screws will likely need readjusted after some running.

I adjust idle mixture by turning each clockwise until cylinder no longer fires.
Then open it up slowly until cylinder fires, then open up another half turn. If cylinder spits through that intake, open up idle adjustent screw slightly more.

Not my work.....stolen from roblav and very well done

I had this issue when I first got my car running,I had already replaced most of the worn linkage ball cups,found lh and rh thread ones new on Pelican,did a couple more and it was sorted.
I also found the throttle return springs were a bit uneven and sorted that,now after a bit more running I have found the issue is sometimes there again so I plan to fit return spring on the cross bar as others have done.
Unless all the above are correct any adjustment of air bleeds, mixture or throttle screws is only masking the problem,good luck.

Before synching carbs, you must disconnect linckage and make sure all throttle plates are contacting bore when closed.

Then connect linkage, and make sure left and right sides are synched mechanically so they begin to open at exactly the same time when connected.

If you don't do this first, all else will be out of whack.

Only then do you go idle mixture screws.

GN

Thanks for the replies, was looking for a shortcut, but alas, will check linkage ball cups, start from scratch. ... wish 'my guy' Klaus was still around... LOL

Here is a great guide to adjust Weber’s
http://www.performanceoriented.com/special-procedures-1

I think its the first job to do,I found the new ones are a really tight fit so I can only assume the cups wear more than the ball ends which appear to be harder steel.
What I did find was the RH thread ones appeared to be more worn than the LH thread ones....weird really ,also I found you can't adjust the drop links to be exactly the same length for some reason,didn't find anything bent so guess that's the way the crossbar pivots are .
I have new throttle cams to fit so I may correct the above @ the same time.