Zenith 32 NDIX pump rod

[Albert Tiedemann]

All:

In 1958 [maybe a few 1957 cars as well] Porsche began fitting the 32 NDIX carburetor to the engine. Early rods featured a center section made from a Cu alloy, perhaps 360. It had turned down ends and one end was longer than the other. The longer end contained the left hand thread [left = long, you know the Germans] The same material was used in later rods but the center section was just a hexagonal rod. The end containing the left hand thread had a circumferential groove to identify same. I am not sure when, but the material was change to a plated steel. I think I even saw some advertised that had a square body, but that cannot be correct.

Anyway, I am trying to determine when the switch from the turned down ends to the "all hexagonal rod" was made. Any input welcome as to when this might have occurred. I have included a sketch of the part. The dimension across the flats[ATF] is 5.5 mm and the diameter of the turned down ends will be that of the inscribed circle of the rod.

Pump Rod Center Section, Old Version.pdf

(30.28 KiB) Downloaded 72 times

[Ron LaDow]

Ab,
When I was doing Zeniths, (and getting some originals though) it seemed anything with '59' date stamp had the full-hex. But I'm pretty sure they were brass also.
When did the carbs change from "Pallas" to "DVG"? Could it have been associated with that?
Brad?

[Albert Tiedemann]

Ron:

Thanks for the reply. My first Porsche was a '59, [in 1960] but I cannot remember a detail that fine until I started making replacement parts for this assembly when I learned that only "complete units" were available to purchase. This endeavor was prompted by "why replace the whole assembly when only the link with the left hand thread was damaged or broken". Many know why and on what carburetor. I did a little more looking regarding my comment about the currently available Zenith pump control rod and found the following of note. My comments are based upon an enlarged picture of said control rod posted on the Stoddard website.

It is clear that the center section, hereinafter "body", is a square and that the nuts are also square and the latter are of equal height. The circumferential groove on the square is not proportionally located on the body as on the bodies with a hexagonal form. In the details posted for this illustration, the source is cited as Genuine Porsche.

Without a Zenith pump control rod in hand from this source, I cannot say if the square body is the correct length or if the machined groove in the body to identify the end containing the left hand thread is the correct width. Whether 5.5 mm or 7/32 inch raw material has been used in the manufacture is a mute point since mill tolerances and plating [if used]tolerances are easily accommodated by the clearance built into the open end adjustment wrenches.

You cannot tell from this illustration if there is any marking on the square nut that identifies it as a left hand nut. The left hand nut on previously offered assemblies of hexagon body and nut form were thicker [by approximately 2 times] and some had circumferential grooves.

Since the threaded links are embedded in the body of this illustration, it is impossible to discern if the left hand threaded link is longer. I guess you will just have to rely upon your tribal knowledge that right hand threads slope left and vice versa.

Also, I will postulate that the materials of construction are steel and that they are plated although the part number reference in the "details" cited above [616.100.809.00 does not wholly support the postulation.

Rest assured, however, if you are entered in a competition in which I have been ask to judge and you show up with this link, you will be downgraded even if you produce the Porsche bag that contained the part as this configuration was never ever offered by Porsche in the vintage years. You might just as well turn up with an emergency link fashioned from coat hangers [be sure to get the cheap metal ones so the diameter will pass the connective link holes] and later to be refined by Harbor freight and advertised as "can be used on Porsche". If you come to the Ski Round top Swap on September 15, 2018, stop by and I will show you just how cheap a reliable link can be made. Think "big iron" as you ponder the choke adjustment link.

See you a Ski Roundtop, Adam, and save me one of your handouts as I am not in the flashlight hunters fraternity.

[Ron LaDow]

Ab,
A day or so ago, I ran a magnet over some 2 dozen links, both partial and full-hex, assembled and otherwise. None of the hex parts were magnetic, so I'm quite certain they are all brass. You can be fooled with a rare-earth magnet on an assembled link, it seems magnetic but as you 'mouse over it', it it obvious the magnet is attracting the steel end-links (and nuts)
There is a repro available here: https://www.pinzgauer.com/showdetails.p ... 7121085289 "Pump Rod Carb Zenith NDIX"
Comments:
1) They are all-steel, which doesn't matter unless you are showing and the judge has a magnet.
2) There is no bold nut on the LH threads, which means you get to fiddle with them on reassembly if you have them clear-plated.
3) They are longer, since the 36mm carbs have a spacer between the float bowl and the throttle body. You may have to shorten the hex part.
4) When I last bought some, the bend radius was too generous, which meant some filing to get the spring/washers/clip on the outer ends.
If you use them and plate them, fit them first. #3 and #4 should be done first.