Dual carb question, Dellorto 40s on a 1.8L to be exact Options

[terrymason]

The problem - The car will go very lean around 2500 rpm, as if the pump jets were too small.

History:
New fuel pump (3.5 PSI to each carb)
55 idle jets
55 pump jets
140 main jets
175 air correctors
These carbs are new to the car, and I'm trying to dial them in.

The car is lean when I first start it (16 / 17 on my air / fuel gauge), but then levels out to a nice 14.7 idle when warmed up. While driving, I can give the car 20% or so of the pedal, and drive up to highway speeds nicely, but when I goose it, it will go very lean (18-22 on my gauge) followed by a series of backfires and loss of power. I started off with 35 pump jets, and have moved up to 55s, which appear to be the most popular around here. I've also adjusted the pump jet linkage, from the nut fully loosened, and moved it in as far as it would go before affecting the main throttle shaft (like 60 turns or something).

What do you guys think, do I need 75 pump jets?

[terrymason]

do you have a wide band o2 sensor? It made it ALOT easier to tell if the things rich or lean. I'm also running 30 vents now.

I'd say get bigger pump jets and swap them out. Pump jets are about the easiest to change.

[bjinright]

do you have a wide band o2 sensor? It made it ALOT easier to tell if the things rich or lean. I'm also running 30 vents now.

I'd say get bigger pump jets and swap them out. Pump jets are about the easiest to change.

I've got some 35s I'll try them first, but I know I'll probable have to get the 50s. I SOLO race once a month or so so the O2 sensor is probably a good idea. I also need to check the etubes, I have no idea what they are. I was always looking for an f11 or f2 but I thanks to this thread I know what number to look for. We should put a thread on here for Dell's showing what a good starting point for different vents are. I've got the Tuning manual but it's very 1600 friendly.

My 1.8 is a eurospec. 8.5 to 1 compression. Factory carbed with wierd bumpers and no side markers. I don't know if it was originally that way but somebady before me made a darn good copy.
CB did not have 30's when I re-vented my dells so I'm sticking with the 32's. The 34's have an off idle stumble, (pretty common on our 1.8s and 2.0s) but if your racing who cares. The 32's have fixed the stumble.

Also Terrymason, I noticed the throttle body of your dell is similar to mine, If i saw it right there is a notch where the secondary vent fits in to the carb body. Not all dells have this. some 2vents have a ring around them like some kind of tiny space station. DO NOT order the update kit if you have the notch. It won't fit right.
OR tell CB that you have a notched Secondary vent body and see if they have another version. they haven't so far. My first set of Dell 40s had the update on them but were a different main body type apparently.