Serial numbers used to date code our 28 PCI carburetors

[BulliBill]

Hi all,

I searched but didn't discover a topic about using the serial numbers stamped into the bowl area of our 28 PCI carburetors to sort of "date code" our carbs. Not sure if others have tried to sort out when various carbs were made and track any improvements made in them. I have a box full of 'em and wondered (other numerical progression of serial numbers) how to basically date code them. A few of us might want to find a carb serial number appropriate to the year the engine was produced.

Anyway, if there is already a thread, please point me toward it, or lets do this!

Some of the digits are a bit hard to read. All of the serial numbers I have are either six or seven digits long. My earliest 28 PCI carb in the box is #722944 and my latest is #4998957

Bill Bowman
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Thanks for any help!

[EverettB]

There is no specific thread about it as far as I know but I have seen it asked a few times.

A recent thread though:
https://www.thesamba.com/vw/forum/viewtopic.php?t=729601
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[Volumex]

Some info here: https://www.thesamba.com/vw/forum/viewtopic.php?t=482472

[Mr. OGPaint]

I'm doing the same thing on a small scale with fuel pumps here
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[oldslow]

28PCI serial numbers:
I too have found it surprising that so little attention has been paid to the 28PCI. After all, it was used for longer than any other carburetor, and may be the most common VW carburetor ever. Millions of 1950’s beetles, busses, and Ghias and industrial engines had them.

I tabulated data on carburetors from TheSamba forums and gallery, as well as from eBay and my own collection.

28PCI’s can be divided into two broad styles: I call them “early” and “all the rest”.

The early style has a ribbed fuel bowl to accommodate s brass float, and the early top piece has a removable brass idle jet (it’s tiny)

The very earliest base had no provision for vacuum. Later early bases had a “D” shaped boss that was not drilled if it was intended for a bus, or drilled and tapped for vacuum if intended for a beetle. The early bases also had an iron grub screw that held the venturi in place. I believe that as production progressed all early bases were tapped for vacuum, and those headed for a bus had a brass set screw to close off the hole.

The earliest bases lacked the “28 PCI” cast on the bowl, and the round VW logo changed from a fat style to thinner lines over time. There seem to be 3 or 4 slightly different VW logos throughout the entire early to late production.

As for the all the rest? Well sometime between #1364556 and #1965149 was the end of the early bases and tops. The later bases had a steady evolution of minor changes for the rest of the 28PCI run. For example one easy change to spot is the words “Made in W. Germany” this was added around #3500000

So how does this help to match a specific carb to a specific engine? It’s pretty obvious that the 36hp carburetors were sequentially numbered with the earliest seen so far from about #70000 to up to maybe #5000000. At a guess something like 4,930,000 numbered carburetors and an unknown number of blank ones were produced. After reading about total production in the archives I calculate that about 3867975 beetles busses and Ghias were produced with the 36hp engine. Add maybe 73000 industrial 36s to bring the total to about 3,941,000. This doesn’t match up to well with 4,930,000 carburetors. Off by a million. Maybe the carburetor serial numbers are sequential but have gaps, so perhaps carburetor 4998957 is the 3,990,000‘th produced. Maybe VW recycled a million 36hp motors and put new carbs on them. Maybe my production numbers are wrong.

We do know a few things though. The first vac advance carburetor (VJU 4 BR 2) went to December 1953 beetles so we can match that with the first vacuum carburetors. Progressive refinements says the brass float was eliminated 03/17/55.

If you have a zwitter it for sure came with the early style carburetor. If you have a ‘59 or’60 it’s going to say Made in W. Germany. 56,57,58? not sure yet exactly.

So all you picky stock lovers out there, go out to your low mileage never modified engine and photograph the carb and its serial number. Post it in the gallery and tell us about it.
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[Dan22]

[janerick3]

I've posted some of these numbers sometime in the distant past, but here goes:

28 PCI:
- 1377021 from engine 20-0922XXX, 12/54, early base, undrilled vacuum boss
- 1436019 from engine 1-0960XXX, 01/55, early base, brass tag
- 1716897, not original to engine, late base, steel tag
- 4650897, believed from 1960 engine

I have 1-2 others buried in my shed w/no traceability
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Thanks,
Jan K.

[Dan22]

Here is a graphical predictor of the carburetor number based on the engine number using the data in this and other threads. The curve looks reasonable given the increasing popularity of the cars and production increases.

If I get other confirmed numbers I can add it and give an update. The formula is there but you have to use an x number based on what excel uses for a date, something like the number of seconds since 1970 or something like that. And you need a scientific calculator for the exponent of e.

I really hope BulliBill posts the carb number on his original June 1955 beetle because my car is also a June car.
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https://www.thesamba.com/vw/forum/viewtopic.php?t=765074