Jetting question - Zenith on 2.2T

nkbitsch · 03-15-2016, 01:32 AM

I've read several places that the stock venturi and jetting size for the Zeniths initially were too small. I've also found a few recommendations jetting/veturi for modded engines. Though I haven't been able to find any recommendations for a standard 2.2T engine.

Some say that factory sizes runs just perfect, but as I'm rebuilding at the moment, and have to order new venturies and jets anyways, I though that I could as well order the optimal sizes.

I've seen that PMO has some recommendations for the Weber IDAs but not for the Zeniths.

Have any of you experimented and found the optimal venturi/jet-size for a standard 2.2T?

Here's a little picture of the beauty having a great time in the ultrasonic cleaner:

VFR750 · 03-15-2016, 09:12 AM

If it is going to stay a 2.2T, including the T cam, then the Venturi size is fine.

I you want more power, like a E cam, then the 27.5mm venturis might be too small. But not by much.

Alfa1750 sells venturis on eBay. I've dealt with David before. Great source for hard to get bits for zeniths. My guess is he has 28-29mm venturis.

VFR750 · 03-15-2016, 09:13 AM

Btw. You left a transition port plug in. See your picture.

nkbitsch · 03:05 AM

Quote:

Originally Posted by VFR750

Btw. You left a transition port plug in. See your picture.

Good spotted!

I simply couldn't loosen it, but I think a thicker screwdriver than the one I had will do the job.

For now, I'm not going for E cams, so I will stick with the stock venturi size.

Though I'm thinking of replacing the jets, just to make sure that it runs smooth. I can see that the stock idle fuel jet is 47,5. But alfa 1750 only sells 47 and 48. What would you go with?

Also, do you have experience with his rebuild kit? I have heard that the gaskets in some kits doesn't fit properly.

VFR750 · 03-16-2016, 03:46 AM

The 47.5 jet is too small really. And the 48 won't make a difference. With modern e10 gas you'll want somewhere around 50-55.

For a 2.2"E" I would go with 50s.

For reference my 3.0 likes 57-60 depending on the state of the engine. My 62 are just a little too much.

Some gasket kits use the weber paper gasket between the top cover and the intake "bowl". I haven't used alfa1750 kit yet.

Yes, you need the really big blade screw driver. Massive craftsman screwdriver in my tool box! I does take some torque to break them free.

nkbitsch · 06:51 AM

OK. I actually didn't know that. How about the other jets? As I could read, this is the default sizes:

Main Jet 115
Air Correction Jet 195
Emulsion tube 4,3
Idle fuel jet 47,5
Idle Air Bleed 165
Pump jet ?

What would the optimal sizes be?

Quote:

Originally Posted by VFR750

The 47.5 jet is too small really. And the 48 won't make a difference. With modern e10 gas you'll want somewhere around 50-55.

For a 2.2"E" I would go with 50s.

For reference my 3.0 likes 57-60 depending on the state of the engine. My 62 are just a little too much.

Some gasket kits use the weber paper gasket between the top cover and the intake "bowl". I haven't used alfa1750 kit yet.

Yes, you need the really big blade screw driver. Massive craftsman screwdriver in my tool box! I does take some torque to break them free.

crummasel · 03-17-2016, 05:10 PM

#1 Open it up at least to 30mm (which can be machined out of the original venturies on a lathe if the operator has a "sense" for fine mechanics), and build your new jetting based on that.
#2 REALLY understand carburettors and jetting profundely and especially the Zeniths.

nkbitsch · 03-21-2016, 06:27 AM

I think I will run with the standard size venturies, and try some different jetting as this is what I have found most people recommending.

I'm all new to adjusting carbs, so I have a steep learning curve in front of me :-).

What would be a the best starting point? I'm thinking of at least running with some bigger idle jets.