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A note from the Technical Committee:
This Topic Index page on the Zenith Carb shows only a portion of the content the 356 Registry's members have had at their disposal for years. The problem has been only a few people could find it easily. Our goal is to organize our technical library with a series of Topic indexes. There are hundreds of topics to cover, and we need some help identifying the articles and writing short description for each page. Please see the New Website Guide page and consider volunteering. No website experience necessary!

The Zenith 32 NDIX Carburetor was introduced in 1957 for the 1600N and 1600S engines, and continued to be furnished through the 356C in 1965. When rebuilt and set up properly, they provide great service for stock and mildly modified 356 engines.

From Ron LaDow:

For street-driven 356s with engines displacing ~1600 to 1720ccs, it is really hard to beat Zenith carbs.

Their design complements 
the 616 engine to provide performance where most of us use it: 2,000 – 5,500 rpm. The factory spent many dyno hours and road-test hours making sure that was true and determining the jetting to do so for the various engine specs. And by design or accident, the transition circuitry is superior to any of the alternatives; you do not hear gripes about ‘flat spots’ regarding Zeniths.

Happily, by 1960, Zenith-equipped 356s were 
fitted with the paper filter elements, so you also get air filtration far superior to any other 356; truly modern tech. But by their design, they are also 
subject to leakage if not maintained and serviced properly.

Reference Documents

Zenith Section - Porsche Factory Workshop 

1958 356A Supplement

Zenith section - Porsche Factory Parts Catalog

Includes notations by Bill Romano

Zenith section - Porsche Factory Workshop manual
356B/C Version

Exploded Zenith Diagram, with annotations  

From Ron LaDow and Charlie White

Magazine and Website Articles


Leak no more: Keeping fuel inside Zeniths - by Ron LaDow

Porsche 356 Registry V40 Issue 6 

For street-driven 356s with engines displacing ~1600 to 1720ccs, it is really hard to beat Zenith carbs. But by their design, they are also subject to leakage if not maintained and serviced properly.

Open PDF

Rebuilding Zenith 32 NDIX Carburetors - by Ron LaDow

Porsche 356 Registry V31 Issue 4

The type NDIX has also been in production longer than any of the stock 356 carbs. Sooner or (mostly) later, they will need attention. But before you decide to rebuild them, make sure that’s what they need and what you want.

Open PDF

Adjusting and Tuning Zenith 32 NDIX Carburetors - by Ron LaDow

Article written for the Porsche 356 Registry Website.

With very few exceptions, Zeniths tolerate all sorts of strange jetting and adjustments and still work OK. They work far better than OK if you spend some time to tune and optimize them. If this is your first effort at tuning carbs, allow a couple of days so you don't end up wasting your time.

Open PDF

Zenith Carburetor Bases: Making Them Flat - by Bruce Tews

Article written for the Porsche 356 Registry Website.

I do not like leaks of any kind, whether they be engine oil, transaxle oil, or gas, and maybe, especially gas. So, my Zenith carbs leaked, and I was not going to tolerate the leaks. Mine no longer leak, and this is how I fixed them.

Open PDF

Developing the Flow in Zenith Carburetors - by Gary Koehler

Porsche 356 Registry V32 Issue 5

I have finished the rebuild and modification phase of the Zenith carburetors for my big bore rebuild, realized some nice flow and velocity gains, and wanted to share what I did with Registry members who are interested.

Open PDF

Replacing Zenith Carburetor Top Cover Gasket - by Steve Dempsey

Article written for the Porsche 356 Registry Website.

Recently I discovered the top cover gasket on my driver side Zenith 32NDIX carburetor leaking. I decided to give it a shot, and as it turns out, this job is really something anyone with basic skills (and a little muscle) can handle.

Open PDF

Carb Chemistry101 - Cleaning Zinc Alloy Fuel Bodies By Bruce Smith

Porsche 356 Registry V37 Issue 6 

Since the invention of the carburetor in the late nineteenth and early twentieth there has been a need to clean the residues and reactants that accumulate during use. How to clean the crud that forms in and on carburetors.

Open PDF

Jet Setting By Bruce Smith

Porsche 356 Registry V38 Issue 3

So you’ve decided to tear down your carburetors and rebuild them. Now the challenge is figuring out whether the jets in your carb are what you need, or even what they are marked to be. Instead maybe you’re looking for some performance improvement from your carburetors. 

Open PDF

Zenith Carb Checks and Adjustments - by Ron LaDow

Porsche 356 Registry V35 Issue 4

As our cars and their parts age, we keep finding new ways in which they have been damaged or have worn out and how to correct those problems. Zenith carbs are no exception. 

Open PDF

356 Resto Strips by Edwin Schweitzer

Concerning Zenith NDIX 32 Carbs

Restoring Zeniths for a T2 Speedster (V36 Issue 2)

Open PDF

Manufacturing new butterfly parts (V36 Issue 5)

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Continued .... new butterfly parts (V36 Issue 6)

Open PDF

Video on Zenith Butteryfly fabrication.

Forum Topic Links - "Best of the 356Talk Forum"

The links below will open a new browser window and take you to a 356Talk Forum Topic. This Forum was established in 2008 and at various times has allowed both members and non-members to post. While many experts contribute to the Forum on a regular basis, there is no guarantee the contents are correct or even safe.

The quality of information is directly related to the expertise of the author. Follow it at your own risk.

How to deal with fuel Seepage

356Talk Forum

How to reduce or stop fuel seepage on Zenith NDIX 32 Carburetors.

Open 356Talk Topic

Changing Venturi Size

356Talk Forum

How to change the size of venturis on Zenith NDIX 32 Carburetors.

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All Zenith Topics

356Talk Forum

This will search the entire Forum for all Topics that include "Zenith" and return a list. You must be logged in to the Forum on this device for the search to work...if you get a message "Sorry but you are not permitted to use the search system" simply log into the forum then go back and hit the button again.

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Heidi & Franny's Garage video covering a tuning Zenith 32 NDIX Carbs.

Heidi & Franny's Garage video covering a full rebuild of the Zenith 32 NDIX Carbs on a 356C.

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