Zenith carbs pros and cons and applicatons?
 

I have a very nice set of 70-71 911t Zentih carbs, may or may need a rebuild. I wonder if they are comparable to webers, better or worse? I have a 2.4 engine that I'm thinking of putting them on. The engine has the following specifications. 2.2 (84mm) E pistons, should be around 9.5: 1 give or take and it has solex cams. Will these Zeniths do a good job on this engine or should I look for good Webers? Maybe PMOS?

Thanks for any opinions.

They are good carbs, but tuning parts are hard to fine. You want 32mm chokes, ( Zeniths have 27) you can modify weber chokes to work. 140 Mains to start out with, you may need to go a bit bigger. 55 Idle jets are good for that engine.

Make sure all the emission & enrichment crap is blocked off on the carbs.

Zeniths
 

Thanks for that response, sounds good. If anyone else has an opinion please reply.

David

You can buy VW solex idle jets and there are some sites that have the mains too. I just use a jet reamer and a gauge and drill my own. The stock 27.5mm Velocity stacks can be hogged out to about 31mm's if it runs out of lungs in the high RPM area, pick up the weber 32's and figure out what that modification that everyone talks about is.....then tell me how you did it!
Thanks,
Nabil

Nabil, You made me go out in the garage and take apart a nice set of webers and pull a choke (some call them a venturi) to see how it fit in a Zenith body.

I have 32mm chokes in Zeniths I'm running in a 2.4E right now. They were chokes I machined down from a set that were not factory Webers parts, that I bought on e-bay.

So here is the scoop using factory stuff. The base of the Weber and the Zenith chokes are the same size and the height is the same. The Weber chokes drop right in the Zenith body.

The only problem is that the top of the Weber choke has a slightly smaller outside diameter. (.5mm) That allows the aux venturi to fall in about 1.5mm below the top of the carb body, where it should be flush.

All you have to do is cut a 1.5mm thick paper gasket ring using a choke as an outline, stick it at the base of the choke hole and all will be fine. Or you could make spacers out of your old Zenith chokes by machining 1.5 ring off the bases.

I used a reamer and a guage to get the desired jet sizes. ( I have a pile of them) I did not know that the VW stuff was the same.

Getting 31mm out of a 27.5 Zenith choke is cutting it pretty close. The O.D. is only 32mm.

Nice Work TVR!!!
I've been needing to go bigger on the venturies for a buddies engine. I told him to run with the zeniths and I got stuck doing to tuning (for opening my mouth). I'll give that a try.
Thanks for the homework!
Nabil

zeniths
 

Thank you for that great info.

David