Effects of going from 30mm venturi to 32

[keitho64]

I have a 2.2 motor that is a hybrid built to a S spec motor. As of now I have 30mm venturis, 60 idle jets, 130 mains, F1 tubes and 180 air correctors. If I were to experiment with 32mm venturis would I need to make any other change to the jetting?

Right now the car runs a little rich at idle with the 60 jets, but with 55 it spits. The transition from idle circuit to main is very smooth as is performance up to 6500 or so. All in all it runs very good, however I am always on the hunt for the optimum setup.

In conjunction with the 32mm venturis, I was thinking about bumping the emulsion tubes to F3.

Do any of you see a flaw in my logic?

[campbellcj]

I have essentially the same engine and recently started tinkering with the Webers too.

Richard @ PMO suggested 32 venturis, 55 idles, 130 mains, 180 air and F3 emulsion. (That is a stock 2.0S setup.)

That is what I have in them now except F26 emulsions instead. Like yours it spits/pops a bit on the idle circuit with the 55's if the mixture screws are set anywhere near where they "should be". But all-in-all it runs quite well now.

I would guess that the larger chokes would bump your power curve to slightly higher revs. I actually had even larger chokes before (34's if I measured right; they're not marked). It seemed like the carbs would "break up" at high revs i.e. 6200+ and that is a bad thing since it's a track car. It's too soon to tell whether it will pull better and smoother with the 32's...

[jluetjen]

ChrisC;
When you put in the larger venturi, did you change anything else like the mains or Emulsion tubes?

[campbellcj]

I put in -smaller- venturis.

When I acquired the engine, it had the larger chokes and the mixture was set incredibly rich. Even with megaphones the plugs and exhaust were somewhat sooty.

I'm hoping to play around with it more this weekend. I think the main jets will be fine but not sure about the idle jets or emulsions yet...

[SteveF_911]

I have a 2.0 s with webers

Setup is
30 mm venturies
55 idle
125 main
180 air correction
f2 tubes

I tried 34 venturies as I had a set lying around. I found that performce at lower RPM dropped off and maximum power was made at higher rpm ie 7,200 which is more rpm than I wish to use.

32 should be ideal for a 2.2s assuming it is not a race car.

If you do any changes put the car on the dyno and check the AFR to make sure the car is not to lean.

Putting bigger venturies will make the engine run a little leaner at high revs.

[Zeke]

A rule of thumb: 4X the venturi size = main jet to start. Depends on cams. Sounds like you can go up to the 32s w/o touching anything since you are already rich.

[keitho64]

I installed the 32's and also bumped the mains to 130 and I am elated to report the car runs better than ever! It idles at ~900, smooth as glass, pulls throughout the entire rev range to 7,500-7,700. Ah I love the wail of a short stroke 911! The performance in the upper RPM is unbelievable. i would never believe a little 2.2 could run like this.

Thanks to all your help the final jetting is:

Idle - 60
Main - 130
A/C - 180
Emulsion tubes - F1
Venturi - 32mm