I grew tired of trying to guess the correct fuel settings on my triple SU E-Type. So I installed a fast O2 sensor in each downpiipe, and an Innovate lambda gauge in the dash. I discovered several interesting things, but the one I want to discuss today is that my rear carb has a tendency to run lean when I push the engine. I’ve sprayed the rear carb and manifold with carb cleaner in an attempt to identify air leaks, but there’s nothing obvious. In discussion on the E_Type list, another member reported the identical issue, and eventually solved it by using a UO needle, just in the rear carb.
I’m wondering if this has something to do with the vacuum takeoff for the brake booster. It’s the ony thing I can think of that’s different from the center and front carbs. Anyone else run into this problem?