Weber Tuning and Idle Increase

[Pinch]

Thanks to Wayne's book and the great threads on this forum, I decided to tune my 911's Webers (46 IDA 3C).

With the exception of cylinders 3 & 6, which both exhibit lower air draw and do not respond to adjustment, everything went ok but when I reconnect the linkage (drop rods) the idle increases to almost 2k. My throttle idle adjustment screws on both carbs have very little adjustment range left (i.e., backed out to the point where they are almost not touching the throttle lever). So how do I decrease the idle?

I've examined the linkage and it seems ok. Because it moves each throttle lever simultaneously, I'm hesitant to fiddle with it which raises another question: according to Wayne's book "The accelerator linkage must open each carburetor by the same amount at the same time..." As far as I can tell, the only way to examine that is by watching the throttle levers move. Is this how you do it? If so, it's a challenge even with stereo vision.

Just trying to figure this out. TIA

[Steve@Rennsport]

Sounds like several issues at work here.

I would first investigate why cylinders 3 and 6 won't respond to airflow adjustment and idle mixture screws. You may have a clogged idle jet, idle air bleed, worn or maladjusted throttle plates, etc. After that's resolved, you can proceed to the linkage issue.

You may need to make several adjustments and I would first adjust the throttle rod between the front bellcrank & the crossbar to get it to idle at 900RPM with everything connected.

Naturally, make certain that the distributor advance isn't sticking and keeping the idle too high.

[T77911S]

+1
from what i had read, and now come to understand, the idle screws are not really to se the idle, they are a mechanical setting. the idle is set with the air bypass screws.
then the way i did my linkage was to connect the linkage then i would raise the idle just a little with the cable to the linkage. (914-6). then i would use the sync to balance left to right carbs with the linkage. since all barrels should be the same, i would use 1 and 4 to compare.

[Pinch]

Thanks for the great advice. I called Paul Abbott at Performance Oriented and he figured out what the problem was right away and guided me through the steps to correct it (it was the linkage). We all know Paul from his invaluable contributions to this forum and when it comes to Webers he is definitely "the man".