Shop car context: VIN 108689's engine had sat for decades. Both Zenith 32 NDIX carburetors were rebuilt with ZE-25K kits — the engine now runs on them. Every photo below is from that bench session.

§1 · What correct looks like

The Zenith 32 NDIX is a dual-throat downdraft carburetor; a 356A Super carries a pair. The castings carry Zenith and NDIX markings — ours are stamped ZENITH W-GERMANY with the NDIX designation on the body.

Cleaned Zenith 32 NDIX casting showing NDIX and ZENITH W-GERMANY stamps
After cleaning: the casting identification — NDIX, Zenith, W-Germany.
Authenticity note: matching carburetor types to your engine spec matters for judging and for tuning literature. Confirm what's actually on your engine before ordering kits — decades are long enough for swaps.

§2 · The kit

One ZE-25K kit per carburetor: gaskets, seals, diaphragm, and replacement hardware. Lay out the kit contents against the instruction sheet before touching the carbs, so you know what’s being replaced and what must survive disassembly intact.

ZE-25K rebuild kit package Kit contents in packaging
The ZE-25K kit as it arrives, and its contents. One kit does one carburetor.

§3 · Teardown — layout discipline is the whole game

The single most valuable habit in a carb rebuild costs nothing: lay every jet, screw, and small part out in disassembly order, and photograph the layout before cleaning anything. Jets look alike; they are not. A swapped idle jet between throats will chase you for weeks as a mystery flat spot.

Jets, screws and hardware laid out in disassembly order Old and new seals sorted side by side
Left: jets and hardware in disassembly order. Right: old seals matched against their kit replacements before anything goes back together.

While everything is apart, record the jet sizes stamped on each jet — that’s your carb’s actual specification, which may or may not match the book spec for the engine. Ours are recorded in the build ledger.

§4 · Cleaning & reassembly

Castings get cleaned to bare, bright metal — passages blown through, no polishing compound anywhere near a fuel path. Reassembly follows the layout photos in reverse, new seals and gaskets from the kit throughout, old parts retained and bagged as the reference set.

Finished pair of rebuilt Zenith NDIX carburetors
The finished pair, ready to go back on the Super engine — which now runs on them.

§5 · What this guide doesn’t cover yet

Bench synchronization, final jetting for the 1600 Super, and on-car tuning happen when the engine goes back into a driving car — that’s a later phase for the shop car, and this guide gains those sections then. Jetting specs will be published with their sources when they’re verified, not before.

Safety-critical: fuel system work. Inspect fuel lines and the tank before running rebuilt carbs — fifty-year-old fuel varnish travels, and a clean carb fed by a dirty tank doesn't stay clean.

§6 · First start

The reason this guide exists: the engine firing on these rebuilt carburetors, for the first time in over fifty years.

VIN 108689's Type 616 running again — first start in 50+ years, on the rebuilt Zenith 32 NDIX pair above. Phone video, low resolution, kept as shot.
Parts used Affiliate links · they fund the research
Carburetor rebuild kit, Zenith 32 NDIX (per carb)
PN ZE-25K
One kit per carburetor. Gaskets, seals, diaphragm, hardware — what we used on both of ours.
Pelican

Where this guide comes from

  • Shop car 1959 356A 1600 Super, VIN 108689 — both carbs rebuilt with ZE-25K kits; engine runs
  • Supplier ZE-25K kit contents and instructions
  • Forum 356 Registry / Pelican 356 Technical — NDIX rebuild threads (synthesis in progress; citations to be added)