BIGRACING

I was wondering if someone could give me some advice on the correct jet sizes for my triple Weber 40ID on a 2.2 liter engine?
I notice from my Haynes manual that the Air Correction jets are generally larger than the Main jets. It's also my understanding that during the years the triple Weber where used, it was for something like a 2.0 liter engine? I have both size engines. How much would the jet setting differ between the 2.0 and 2.2 liter engine?

Besides many other weber adjustment parts, I also have an extra set of some very long pre-atomizers to choose from. What are the advantages/disadvantages between the standard 4.5 pre-atomizers vs. the ones that meet up with the top of the Air Horns?

Any advice is greatly appreciated.
Happy Turkey Day,

Raoul.

Steve Weiner-Rennsport Systems

Raoul:

Jetting depends on many things:

1) Displacement

2) Compression ratio

3) Camshaft profile

4) Exhaust system

5) Carb main venturi size


As you can see, two engines with same or similar displacement can require different jetting based on the above parameters,....

The answer to your question lies with how each engine is configured.

BIGRACING

It's NOT for a racing application, and everything is pretty much standard.
1) Displacement = 2.2L
2) Compression ratio: let's say it is 10:1
3) Camshaft profile: Stock
4) Exhaust system: custom (sort of like straight back, into one short exhaust)
5) Carb main venturi size: 40IDS (I've got to double check, but I thing it might be a 46mm?)

I got the carbs back from Motormeister (long story) with 120's in both the Main and the Air Correction jets. This worked for a while, about 2000 miles, until the engine was broken in. It now seemed the engine was starving for fuel, especially at the top end. Then I tried some 168's that I had laying around in the basement, in both the Main and the Air Correction. Initially found myself using about 1 gallon of fuel per 10 miles of travel (I only have a 3 1/2 gallon gas tank) After some adjustment it's down to about 45 miles a tank (vs. the about 60 miles I used to get before) Now the top end is nothing to complain about, but I like to avoid 'washing down' the cylinders with to much fuel. At this point it also doesn’t start to good.

What I'm looking for are some initial guide lines to start with, let's say for a stock 2.2 engine.

Before I take the thing apart again, I was also locking for some more info on the difference between using a long, medium or short pre-atomizer. My Weber Carb HPBook, nor my Haynes manual seem to have a lot of info on that particular part.

Thanks,
Raoul

Steve Weiner-Rennsport Systems

Raoul:

LOL,..One must really have some precise information to properly choose jetting,...

No 2.2 came at 10:1 CR, if you really have that,....do you know if you have Mahle or JE pistons? CR is critical here.

"Stock" cams. 911's came with either T, E, or S cams. All of these are "stock", but they are VERY different.

I don't mean to be difficult, but one needs some detailed specs to make this call.

You should be using either 170-1750-180 Air Corrector jets, but mains will vary with camshaft, compression, and main verturi size.

Look at your engine build sheet or contact the builder to get this needed info.