JowettTalk

On eBay are carbs suitable for fiat 128, hence in my opinion possibly a good replacement for Jowett Zeniths.
When I enquired where & what brand they were the supplier said they were generic & made in Chine of the best quality.
These are 1/2 the price of new webers, has anyone any experience with these carbs or similar generic carbs?

All carbs must match the engine. There are many variables. The first is the fixing to the head. Usually you need an adaptor. Then there are the controls, such as throttle and choke. These usually need modification. Jowett carbs are handed.
Then you need to look at port and throat size.
Then all the jets where there are always three but may be two or three more.
If Zeniths are properly refurbished they are adequate, although they do run out of steam above 70mph. Note that fitting new bushes in the throttle is always required and this has to be done very accurately otherwise slow running is impossible to get correct. You should not be able to see any light when looking down the barrel with a closed throttle at a strong light source. New butterflies may need some bedding or lapping in to achieve such closure. Jets can wear so checking their aperture is also a good idea for accurate metering. But for most purposes such accuracy is lost amongst the confusion of different petrols and modifications to the head that have occurred since the design of the car. There is quite a lot in the technical notes on the subject.

Look for Weber 32 for 50's and 60's Fiat. A nit rare and getting pricey. 34 ICT or ICH (one without, the other with a choke), but look for ones without the power valve in the top. 34s can be found new, but the old ones were the prefered swap on VWs back in the day are better quality and easier to tune. With all old carbs, check the slop in the shaft with the throttle closed.