Tuning webers - can't get them balanced

[Christien]

I can't get the 2 banks of carbs balanced. They were close when I started then things started going wrong so I baselined everything and started from scratch. I started with the air corrections screws and the closest I could get was a reason of 7 on 1-3 and - bit above 5 on 4-6. The correction screws were almost closed on 1-3 (1/8th turn out) and way open on 4-6 (3+ turns out). I couldn't even them out with the idle stop screws - the left bank screw was off the stop and the right one just barely on. And even then, I couldn't get the idle below 1000.

I know it's something in the adjustment, because before I started, the idle was at 900 and the idle stop screws had plenty of travel to lower. Now ican even back both screws off the stops and the idle doesn't drop below 1000.

Another new development is run-on. I turn the key off and the engine still runs. That's new. I do have an msd 6a and I know run-on can occur with that box, but I've never had it before until today, after messing with the carbs.

Oh, and on a test drive it felt slightly down on power. Before adjustment, there was a very slight hesitation I believe getting off the idle jets on the transitions, hence the reason for adjusting them. I was expecting to find a little bit more power, not less. (they hadn't been adjusted since rejetting for the 3.0l.)

Thoughts?

[T77911S]

here is a starting point from the website below.

8.Initial carburetor settings to be adjusted as follows:
a.Throttle stop screws adjusted all the way out and turned back in until they just touch the throttle arm and then turn in 1/2 full turn. Alternately: Remove the plugs covering the transition holes (Item #55 on the Weber Parts web page) and adjust the throttle valves until the bottom edges of the valves just begin to uncover the lowest progression circuit holes.
b.Idle air correction screws are turned in until they lightly bottom out and then turned 2 full turns out and locked in place with the 8mm lock nut
c.Idle mixture screws are turned in until they just bottom out and then turned out 2 full turns
d.Connect cross bar linkage and drop links to just snap onto the throttle levers without binding, these will be readjusted later but for initial starting it is handy to have these connected.


make sure the linkage is not effecting one side. i use to pop one side off just to make sure. then i would connect it back up and adjust the linkage so both sides where balanced just off idle using the linkage. you have to keep the RPM's low so the sync does not peg.

here is a GREAT website.

from what i understand now is that the idle stop screws should not be used to really set the idle. once set, leave them. the idle is then set with the air correction screws.
wish i would have known this back when i had carbs. now i can look back and see how trying to use the idle stop screws to set idle was causing other problems, like the mixture screw not having any effect on th mixture.
Weber Carbs Technical

[Christien]

Yep, set everything at baseline, then went from there, air correction screws then idle mixture, then readjusting everything one thing at a time.

On the upside, run-on seems to have stopped.

[turbo grey]

Noticed your not to far from me.Im in vaughan.I have had very good success tuning my webers.Theres a good clip on youtube with a guy setting up a vw motor with webers using a uni-sync tool,and he explains how to use the idle stop screws to balance both banks as far as achieving an even reading.I would start your baseline air correction screws 2 turns out,air/fuel mixture 2 turns out.back the idle stop screws and turn them in until the just touch,then anouther 1/2 turn as the previous member mentioned.from there start the car and start take a reading from the left bank stacks,then the right side.then i would adjust the idle stop screw on which ever bank has the lower reading.from there u can fine tune each stack with the air correction screw.then finally your idle air mixture.oh yeah and all this with the linkages disconnected at the carbs.lastly youll want to adjust your linkages as well.so that both carbs open at the exact time.hope this helps
found the link for you.

http://www.youtube.com/watch?v=5tigMg-Fn94

[1QuickS]

STE readings are VERY high, typically they should be around 4.5 when lean best mixture adjustments have been achieved.

[rw7810]

Send me your email address and I'll send you a very good step by step instruction sheet.

[al lkosmal]

Based on your description of airflow, air correction settings and idle stop settings on 1,2,3 vs. 4,5,6....I'm thinking that you may have a vacuum leak on the 1,2,3 side.

regards,
Al