Zenith 38 39 NDIX ?

[Frederik]

I have 3 NOS NDIX carbs, two have "38" cast on them and one "39". Can this be used on vw? Wonder what the difference from the normal 32 are?

[spencerfvee]

[Danwvw]

What is the spacing on the carb base to manifold bolt holes? If it's the same then some VW NDIX-32 manifolds could be opened up. Probably need a 94mm bore VW engine though to use that much carb. Those carbs though on a Aircooled are going to be a fire hazard with all the coughing and spitting they do.
Zenith Manifolds vs Weber DCNF manifold for Zenith NDIX 32 Carbs
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[Frederik]

Well I bought them with the hope they might get to work with a 36hp/ww okrasa build. Might have to trash thad idea.

I've never heard of 38 (or 39 NDIX).

39

38

However the carb itself is smaller in diameter

Also noticed two looks the same (One 38 and One 39) the second 39 missing:

With both the 39 the 3.. is grinded off and 9 being added (probably 38s thar been modified.

Here are something else I don't know what it is, when the leveler is puched it opens a large Valve to where screw (nut) driver is pointing.

[Danwvw]

Those are really cool carbs. The hole pattern looks the same. Measure them. I have some 32 bases and can see what they measure between bolt holes. Yours would need to have 22.5mm venturi's maybe 24mm if you up the compression.
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[Danwvw]

I have not seen one like that, that's the idle enrichment valve, Not needed with duals.
SS Dual Port 1600 manifolds for Zenith NDIX-32mm
48.5mm center to center

83mm

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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[Frederik]

Thanks, Yes they have the same bolt pattern.

[Frederik]

[Axel Andersson]

I think that NDIX 38 was mounted on some Panhard cars.

[sled]

38 NDIX was used on some Pinzgauer's as well.

keep in mind the 32 NDIX was big enough to support 75hp from the Porsche 1600cc super and C engines. So, unless you have larger displacement or are shooting for more horsepower (very high RPM), then a 32 NDIX is plenty.

Matching carb size, and more specifically carb bore size/venturi size to a given engine's air/fuel requirements, is most important. Over-carbing does nothing but hurt performance.
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drive your split.

[Frederik]

Thanks again for the info. Can I change the throttle base and use smaller venturi? But I starting to understand this is not a good twin carb setup for my little 36hp engine.. Maybe as sigle carb setup for a larger engine? (I have two NDIX 39 and one 3.

[Danwvw]

People figure out how to run all kinds of vintage stuff on a 36 horse. Makes me wonder if anyone has tried big ones. I really like the looks of the Solex P40-11's which are 40's on a dual port Okrasa head 36horse based engine. So those would work if you can find the parts. The venturis may have the mm size on the top lip of the venturi where you can see it.
An Okrasa engine with a 69.5 crank or a 74mm crank with 7.5 or a little higher CR could use them. They would need a bit of attention jetting and it's likely unless you up the bore size and valve size on the 36 horse Okrasa engine they would not handle full throttle.
Zenith NDIX-32:

Solex P40-11:

Zenith to Okrasa Manifolds:

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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[JeeWee]

I am running those 38 NDIX carbs with a 28mm venturi on a 36hp 1448 (72x80) ww okrasa engine with modified Steffi G manifolds. Mine came from a Hotchkiss.

runs great, during the petermax muller rennen on the autobahn 80mph with roughly 50% throttle, nice!

but I have never seen a 39.

Still need to put my car on the dyno to get a proper read

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1192CC WW okrasa
48,2 DIN PS (58SAE HP)@4430rpm - 83Nm@3610rpm

[[email protected]]

[JeeWee]

yes I can.

I took the throttle body of the zeniths and removed the butterfly valves

Then I positioned it on top of the manifold and draw a line with a scriber pen.

then I started with the dremel to 'flow' the manifolds

and this is how it ended up

In meantime I just fit the throttle bodies on the manifolds and then feel with the fingers how the flow will be and remove the obstructions to improve a smooth airflow.

I followed the same 'principle' for the other side, the side where the manifold is mounted on the cylinder head. It took me a lot of time, but it is very satisfying.

There is enough material on these manifolds to do this.
_________________
1192CC WW okrasa
48,2 DIN PS (58SAE HP)@4430rpm - 83Nm@3610rpm

[[email protected]]

That's awesome...i was thinking of using zenith 38s on my 40hp 1500cc okrasa build ...but was wondering if manifolds can be opened up and you cleared that right up 👍 ... I thought maybe they wouldn't and I would have to make custom manifolds but I guess not 👍👍 ..now I got to look for some zenith 38 carbs 🙄

[Frederik]

I don't plan to build any big bore 36hp to start with. My plan is to use one of My industrial engines, with a WW okrasa kit I have. Maybe add domed top 77mm pistons and ratio rockers. What I understand the included solex copy carbs dosn't work good out of the box. Thought that it was a bit boring to have copies reworked, so first I thought of buying old 32pbic's. But I also have this pair of 39 NDIX (and a single 3, and two solex pII. Might however be best to find a pair of 32's.

I don't know if I'm going to keep the 39's if I go bigger or not.

[Alstrup]

On a "stock" displacement Okrasa type engine with stock cam and CR you will be better off using 32 ndix. There is no idea in using 38´s as they will only make the lower rpm area less easy to work with. More cam, CR and displacement and you begine to be able to exploit them.
The 38´s were also installed on some 2,6 l. BMW industrial engines. I never figured out why they went 38 mm when they kept the venturi 28. It does not make sense to me. I have also never come across 39´s, but I see where the flow improvement ideas for the 32 & 36és came from now.

[JeeWee]

Hey Alstrup, I think I have to agree with you. I would love to test both the 32's and 38's on my motor and see what differences are shown on the dyno. Ok I have 8,0:1 CR, ww okrasa cam, 1448cc etc, and have to say they do better then expected in low RPM's. I am running stock WW orkasa valve size 33x28 But it might be the case the 32's do better then 38's, but I came across these and thought it would be so cool to run 38's. There are a couple of guys running 40's (weber/solex) on 69,5x80mm combo's so I thought let's give it a try.

Anyhow what venturi size would you run on 38ndix on such a setup?
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1192CC WW okrasa
48,2 DIN PS (58SAE HP)@4430rpm - 83Nm@3610rpm

[Frederik]

What would be a fair Price for the pair 39 ndix and the single 38 if I deside to sell them and get 32 ndix instead? The other choice is to keep them if I go bigger in the future and just run the solex 32 included in the ww okrasa kit.

The 38 ndix is NOS but the the two 39 ndix (at least one) is probably used little or rebuilt.