Help, only 3 Qs for Weber masterbrains: I think these are easy.

[marlinaness]

I just got what I think is a 2.2 T standard motor and I just put on Weber carburetors. Everything about the engine is good, e.g. ignition, 4.5 psi fuel pressure. The carbs came off a different 2.4T engine. I have just tuned and synced the carbs and they are set up as follows.

2.4T 30 130 180 60 F26

I used an LM2 on all cylinders to get the idle circuits the same for all. They are all around 13.0 give or take .4 up to 3000 rpm. When I test for high speed with the LM2 on cylinders 1 and 4, I have A/F around 13 all the way up to around 3300 rpm and then it goes lean on me up way past 20-40 A/F with resultant popping and snapping, spitting etc. Obviously, I only tried this very briefly.

According to experts, I should have the following:

2.2T 30 125 180 55 F26

Q1) Will changing the setup to the 2.2T setup help my lean condition e.g. change to 125 mains and 55 emulsion tubes? Doesn’t seem like that is the right answer. It seems like I need to get more fuel at higher RPMs or reduce the air intake. I don’t want to screw up the idle set up. It is fast and powerful right now up until 3300.

Q2) Or should I actually increase the mains to get more fuel to reduce the lean condition?

Q3) Or should I reduce the air correction jet fix the lean condition?

Q4) Or should I do both 2 and 3.

I do have 27 venturis on hand that I could try if that is an easy fix.

Many thanks for your continued support.

Marlin

[jpnovak]

If you have an AFR that high then you have more serious problems compared to slightly missized main circuit jets. It sounds like you have a plugged mainjet passage(s). The one-size change in jets will make a relatively minor change in AFR. If you are jumping from 13 to 20+ then you are just not getting any fuel.

I would solve that problem before moving on to fine tune the jets.

[911pcars]

At rest, you should be able to observe fuel discharging from each carb throat while reving the engine. If so, the main jet path is fine. A better simulation is when the engine is under a load (chassis dyno). If fuel discharges okay at 3000, but doesn't when it goes leaner at a higher rpm, suspect your fuel delivery system (pump volume, lines, filter).

Sherwood

[marlinaness]

thanks guys. very good points.

what was interesting is that I had very good fuel delivery at 4.5 psi to the carb inlet. Nice full flow. So, I think it is with the carbs.

Both 1 and 4 were almost identical on all the readings with the LM2 on each, and most of the others were also popping/snapping over 3k. So, I agree that this is something systemic and not one off. Unfortunately, I had to travel to NYC today and can't check again until the weekend.

thanks again

[john walker's workshop]

the little venturis up top will plug in two ways. one way blocks the fuel delivery from the mains. the outlet tube, if you look down the hole in the venturi, needs to be on the side toward the emulsion tube/air corrector hole.

[marlinaness]

John,
thank you very much for responding. Do you mean the upside down big T looking thing that slides in over the venturi? I think most of the pictures shows this to the left of the float in the parts pictures.
thanks in advance
marlin

[911pcars]

Originally Posted by marlinaness

John,
thank you very much for responding. Do you mean the upside down big T looking thing that slides in over the venturi? I think most of the pictures shows this to the left of the float in the parts pictures.
thanks in advance
marlin

Its a secondary venturi. Only one side has a passage that connects to the float bowl/main jet. If the venturi is installed 180º incorrectly, the main discharge tube outlet passage is blocked, preventing fuel from entering the venturi. That condition would certainly create a lean condition. 3000 is about the correct rpm when the carb delivers fuel as the idle circuit transitions to main metering.

Sherwood

[marlinaness]

Sherwood, John, et al,
thanks a million
I will check them this weekend.
regards
marlin