help with 2.0 weber carb jets, I'm soooo confused!! Options

[BK911]

I have two different charts that give two different settings:

28 vents, 1.35 main and .55 idle or
32 vents, 1.45 main and .60 idle.


Bought a set of EMPIs for a 2.0 which came with:

28 vents, 1.25 main and .52 idle


Read MANY threads here, samba and type4forum on proper jetting and vents and they are all over the place.

Would like to get these together and installed asap.

Is the current set up good enough for daily driving to/from work?
No track, no AX, just cruising around TN back roads.

[Elliot Cannon]

The only help I can offer is to share my experience with my 44idf Webers. My engine is 2.2 liter type IV. My carbs are set up with 32 vents, F11 emulsion tubes, 130 main jets, 175 air jets and 55 idle jets. When the engine was first built it ran great once past about 2200 rpm. Prior to that it would NOT come off idle very well at all. A change of Idle jets pretty much solved that problem. About the best advice I can give is to buy, borrow or steal something to measure air/fuel mixture. This device and test drives might help you decide the jetting combination you want. It may take a bit of experimenting (and patience) to find the best combination for your engine but I think you will eventually get there. Good luck.
Cheers, Elliot

[aggiezig]

Bought a set of EMPIs for a 2.0 which came with:

28 vents, 1.25 main and .52 idle

Are they 40 or 44's? Will make difference in jetting. What cam are you running in your 2.0L?

[nditiz1]

If they are 40s you want to start with a base of 28 vents , 115 main, 50 idle.

You can pull the main stack and solely drive around on just the idle to get a feel for the idle jets and where they will drop off. There are overlaps at each stage of the progression and you want to dial in each stage for best overlap in performance

[BK911]

40s on a bone stock 2.0.

[rhodyguy]

The 40s with the 28mm venturi. Good response off idle. Pretty good mileage. Put them on and see what you get. Swapping jet and such is simple with the carbs installed. New linkage? Don't forget the phenolic FI intake bases.

[IronHillRestorations]

I'll 2nd the set up with the 28's

[MarkV]

I don't know my Delorto 40's came with 28's and it drove like a vw bus. I changed to 34's. (IMG:style_emoticons/default/confused24.gif)

[porschetub]

(IMG:style_emoticons/default/agree.gif) with Perry,that jetting is a good starting point,those vents will provide good response and power in the normal driving range @ the expense of small power loss @ rpm you rarely use.
Keep the fuel pressure around 3psi and the engine properly tuned and you will have a nice running motor.

[amfab]

I have two different charts that give two different settings:

28 vents, 1.35 main and .55 idle or
32 vents, 1.45 main and .60 idle.

Here is a thread on this topic:

http://www.914world.com/bbs2/index.php?showtopic=89838

I am definitely no expert, but I too was looking for an easy answer for my 2.0.

After lots of searching I came up with some info from Solex and Mark Harney to add to your confusion.

What I gleaned was that jetting for a particular set up can vary and you need to mess around with your particular motor and driving style and power band desires.

But:

Solex has a formula for carb barrel sizing that says the barrel size should be .82 times the square root of the of the size of the cylinder in Cubic centimeters (2.0L divded by 4 cylndars=500cc) times the max RPM of the motor (5600 for a stock 2.0) divided by 1000—so 5.6.

I will show the work:

500cc x 5.6=2800
Square root of 2800 is 52.92
52.92 x .82 (the Solex coefficient) is 43.39

So Solex is saying that a 40–44 diameter bore is a good size.

Then Mark Harney’s formula says:
Idle jet-1.6 x venturi
Venturi-3-5 less than intake valve diameter (42 on a 2.0)
Main Jet-4.2 x venturi size
Air Corrector-200 as a starting point

Based upon the above information for 40idf a good starting point is:
Idle jet-54.40 (round to 55)
Venturi-34.00
Main Jet-168
Air Corrector-200.00

These are just the best generic formulae I could find. Many people around here have A LOT of empirical experience with this so read their feedback.

According to these formulae I should run in a 36idf (rounded):
Idle jet-55
Venturi-34.00
Main Jet-150
Air Corrector-200.00

But I can't get a 34 venturi in a 36IDF like the Solex formula suggests so with the 32 venturis, using the Harney formula I should run:

Idle jet-50
Venturi-32
Main Jet-150
Air Corrector-200.00

I never got to do this because I pulled the car off the road due to rust issues, but the formulae seemed to reflect the problems I was having with my car.

The car popped a bit on deceleration—lean—indicating the idle jet is too small.
Power got a little flat toward the top indicating a little bigger min jet may have helped
My set up was
Idle jet-47.00
Venturi-32.00
Main Jet-145.00
Air Corrector-220.00

So my symptoms are exactly what the formulae would have predicted.

Of the two options you suggested, I think the 32 vents, 1.45 main and .60 idle would be the closest to what the above formulae suggest. I don't know if you can get 34 venturis.
I think that the suggestions about the smaller venturis are probably better suited to the smaller valve heads of a 1.7 or 1.8 or type I motors. The 2.0 heads have a big intake valve.

I would probably start with:
Idle jet-50 or 55
Venturi-32.00
Main Jet-155–165
Air Corrector-200

Again, there are many here with a lot of experience with this—way more than I have. This is just some info I researched that I hope adds to the conversation.

-Andrew

[MarkV]

They come new with 28mm vents... mine did. I ran them for a long time. Maybe if you are in to fuel economy and you only drive at low rpm you will be happy. I can tell you from experience that w/ 28's you give up pretty much all performance at mid to high rpm.

I started with:

28 vents
.65 idle
1.22 main
195 air

Changed to:

34 vents
.60 idle
1.32 main
180 air

Of the two choice you posted I would go with the 32's but I think a 1.45 main might be too big. The .60 idle you list should be good.

[rhodyguy]

Op states 'bone stock 2.0'. I think the cam will be the limiting factor. It's going to runout of steam at the top end and I doubt he's going to run around @ 5.8k. Not a racer or ax'er. Driveability is the key.

[72hardtop]

40 IDF's on a 2L?

28mm vents
47.5 - 50 idle jets (elevation near sea level or slightly above?)
120-125 main (likely 120)
180-190 air correctors
F11 tubes

Drive-ability when going to a performance carb such as an IDF is a bit of a trade off. Performance generally equates to less drive ability overall. No carb heat would be one thing on those brisk cool days.