Basic Weber tuning woes

[Tremelune]

I rebuilt the Weber 40 IDA 3C carburetors on my 1970 911T 2.2 (after adjusting the valves and doing the ignition timing) using the Parts Klassik kit (which was complete and seems to be of high quality), and now I'm trying to tune them on the car. I cleaned out the passageways with pipe cleaners, carb cleaner, and compressed air. I soaked everything brass in Carb Dip and then put everything including the carb bodies in an ultrasonic cleaner with Simple Green.

My first immediate question is: What is a good starting place for the air correction screws (the ones with the lock nuts)? I have them one turn out from all the way in...an arbitrary location I just made up in my head.

I've got all cylinders drawing about the same air, according to my unisyn.

This is my jetting (it's stock, as far as I know):

venturi - 30
main - 125
idle - 55
air correction - 180
emulsion tube - F26

These are the procedures I'm following:

Performance Oriented

https://www.pelicanparts.com/techarticles/101_Projects_Porsche_911/29-Carburetors/29-Carburetors.htm

It certainly runs better and smoother than it did before I cleaned the carbs, but judging by the smoke coming out of the tailpipe, it's running very rich. When I turn the mixture screws in, the idle doesn't always change noticeably. On some cylinders I'll turn them all the way in with no pronounced effect.

I'm almost certain the engine internals are stock, and the only jetting I changed was to switch the emulsion tubes from F3 to F26 and replace a few mismatched air correction jets (that I believe had already been drilled out to 175 or 180), so it's either just a tuning issue or something bigger inside the engine...I'm hoping for the former.

This is my first time tuning a carb on a 911, and I'm out of my element...The Performance Oriented guide is Very Involved, and the Pelican guide is rather...blasé...I couldn't find a video.

[Tremelune]

It seems the idle air bypass/adjustment/correction screws should start all the way in:

Baseline settings for weber carbs

Perhaps ignore this thread for a bit...

I sure wish there weren't three names for each screw and jet in these things...

[Gordo2]

You have a great reference with Paul Abbott's (Pelican member "1quickS") / Performance Oriented tuning webpage info.

Information well worth downloading, printing, studying and comprehending if you want to DIY tune your carbs.

Answer to your Q regarding idle air corrector setting is addressed on the site BTW:"Typically the idle mixture screw will be 1 ˝ to 2 ˝ turns open, the idle air adjusting screw will be zero to one turn open"

Another priceless tip I picked up from Mr. Abbott is using a Colortune tool to assist in tuning. Here's a video I made to show what it is / how it works:



Lots of info out there, it just takes time, study and patience to absorb & apply.

Good luck, keep at it.

Gordo

[snbush67]

Performance Oriented

I think you may have skipped one of the pages on the performance oriented page. Pay close attention to the initial settings and installation. Information such as the initial air screw settings are in paragraph 8.

[1QuickS]

PM sent.