This set of Webers is very special since they were produced for the very first of the 911S engines.  They were identical to the 40IDA3C Webers used on the Normal 911 engines except they were re-jetted for the higher performance 911S engines.  To identify this jetting change the ends of the throttle housings were stamped with a "S" to identify the jetting differences from the Normal 40IDA3Cs.  Later in production the 911S engines were suffering detonation issues at sustained, high speed operation so the 40IDS3C version of the Weber carburetors were produced.  These upgraded carburetors used a secondary fuel delivery that was activated by high engine intake air-flow and supplementary fuel was delivered via "High Speed Enrichment Tubes" which are the most obvious change to the standard Weber.  Upon adoption of this design revision for the 911S all subsequent throttle housings incorporated the cast-in provision for fuel galleries to feed the 40IDS3C version and its High Speed Enrichment tubes.  Non-IDS throttle bodies simply did not machine the internal passageways.

This set and other early, pre-40IDS3C throttle housings will have the same appearance in the areas around the accelerator pumps; there are external fuel galleries supplying fuel for the accelerator pump jets and no gallery provision for the High Speed Enrichment Tubes.

This set of early IDA(S) Webers are shown mounted to an equally scarce set of sand-cast intake manifolds which were quickly developed for use when Webers first began to replace the Solex 40PI carburetors.  The Webers were already developed for use by Porsche on their 906 prototype race engines but the permanent molds for die-cast manifolds had not been created so an expedient solution for quick delivery was to use sand-cast manifolds.

Other details of the earliest 40IDA3C Webers include:

-The throttle housings and top covers for these Webers did not have any finishing operations so they have the as-cast aluminum color.  Starting in 1968 these components were given a protective "Alodine" coating that is easily identified by the brown/green tint.  These housings were finished with a clear Alodine finish to help preserve them from corrosion and discoloration.

-Fuel inlet banjo fittings are of two piece construction with a cast body and the nipples are installed by soldering.  It is most probable that the cost of manufacturing was decreased by making them a one piece casting which is why the next generation design has a shorter collar between the nipple and the main body, there is no need for a longer collar for the solder connection of the earlier version. 

-Black safety wire of correct gauge installed per OEM tying method

-Black grub screws retaining the main venturis

-Shaft couplings are "folded-spring" of the earliest version.  There were two versions of the folded-spring coupling before the cylindrical shaft coupling was adopted; the earlier version incorporated notches used to keep the heads of the clamping bolts from twisting during tightening of the nuts but these notches were stress risers and in a spring steel component, any stress riser is a poor design which leads to breakage. 

-Black throttle return springs (the throttle-shaft, concentric springs at each end of the throttle body)

-Tall Weber original nylock hex nuts used for M5 studs, these are NLA. I have collected good, used nuts over the years and refinished them for installation on this project

-The split lock washers used for locking the hex nuts on the accelerator pump covers are OEM, heavy cross-section and have the serrations on the faces in contact with the nut and the top cover of the pump (hard to find these also, very specific to early Weber carbs and NLA)

-The accelerator pump rods are NLA and OEM; I have been able to acquire a few in excellent, used condition over the years so I could use them on special projects like this one

-The top covers of the throttle bodies are correct to the main bodies; top cover casting design changed forever as did the main body castings upon introduction of the IDS throttle bodies in mid 1966

-Accelerator bodies and top covers are left as "as-cast" zinc finish but internal chambers are modified for venting per later versions

-Accelerator pump covers are early style without stiffening rib around their perimeter edges

-All studs are of the earlier version with machine-cut threads and radiused ends; later studs had roll-formed threads and sheared ends

-Main venturis, squirter nozzles, squirter nozzle bolts, main jet carriers, fuel bowl drain bolts, idle jet carriers, banjo fittings, banjo bolts, idle air screws, mixture screws and progression port plugs are period correct and OEM.  Again, I collected good condition, OEM parts in anticipation for use on a deserving project like this.

-Nickel plating used on:

     -Lever arm and fulcrum pin installed into the top covers of the accelerator pumps

     -Cam lever that is mounted on the float bowl that operates the lever arm in the top cover of the accelerator pump

     -Intake air horns

-Air horns are period correct with thick flanges and spun, not brazed construction

-Brass spacer washers installed between nylock nuts and flanges of air horns; these are not shown on any Weber drawing but were installed as by Porsche

-M4 cheese head screws used for installation of air cleaner are OEM original screws, new screws do not have the same head profiles as original ones have

-The fuel line ferrules are not OEM, unfortunately,OEM Cohline ferrules were not available to use for this project so I created replicas and zinc plated them with a yellow chromate finish as was original

-All hardware and studs are zinc plated with silver finish as was OEM except for black, yellow and nickel finishes as mentioned above.  Cadmium finishes were not used on Weber carburetors and this has been documented rather carefully.

Finishes and details for mid year, 1967 911S

This set of IDS Webers were installed in June 1967 and show evolutionary changes in finishes and features from the IDA and IDS carburetors as introduced in March, 1966.

In no particular order:

Throttle bodies are as-cast aluminum and not treated with the yellow/gold finish

Air horns are nickel plated

Short throttle shaft end plates are finished in silver zinc plating

SEMS screws for high speed enrichment tube installation are silver zinc plated

Accelerator pump cam lever, top cover pin and the roller lever arms are nickel plated

All spring steel pieces are black oxide finished (typical)

Remainder of steel components including throttle body studs are zinc plated and yellow chromate finished including grub screws for the main venturis

Accelerator pump cover is early style without the reinforced edge

Accelerator pump bodies and top covers are zinc plated and finished with yellow chromate

The "folded-spring" shaft coupling is the updated version without notches for fixing bolt head retention

The accelerator pump cam-lever arm is the later style, IDA type with the longer lever arm and designed for use with the adjustable pump rod

The idle jet holders are the early style, non-o-ring type

The mixture screws incorporated cup washers with o-rings

Included are the rare to find, brass washers used between the air horns and the nylock hex nuts

The accelerator pump rods are the adjustable version unlike the fixed-length links used on earlier Webers

The fuel line ferrules used at the nipples on the banjo fittings are Cohline and are slip-on and not crimped

Finishes and details for 1968 911S

This set of IDS Webers are finished as delivered on 1968 year model 911S cars.  Particulars of this set are discussed following the details of OEM finishes are outlined.

In no particular order:

Throttle bodies are as-cast aluminum and a protective finish applied rendering them to have the yellow/gold finish

Air horns are nickel plated

Short throttle shaft end plates are zinc plated and finished in yellow chromate

SEMS screws for high speed enrichment tube installation are zinc plated and finished in yellow chromate

Accelerator pump cam lever, top cover pin and the roller lever arms are nickel plated

All spring steel pieces are black oxide finished (typical)

Remainder of steel components including throttle body studs are zinc plated and yellow chromate finished including grub screws for the main venturis

Accelerator pump cover is late style with the reinforced edge

Accelerator pump bodies and top covers are zinc plated and finished with yellow chromate

Cylindrical shaft couplings replace the "folded-spring" couplings as supplied with earlier carburetors

The accelerator pump cam-lever arm is the later style, IDA type with the longer lever arm and designed for use with the adjustable pump rod

The idle jet holders are the late style, o-ring type

The mixture screws incorporate cup washers with o-rings

Included are the rare to find, brass washers used between the air horns and the nylock hex nuts

The accelerator pump rods are the adjustable version unlike the fixed-length links used on earlier Webers

The fuel line ferrules used at the nipples on the banjo fittings are Cohline and are slip-on and not crimped

This set of IDS Webers were modified fur use on a very original 1968 911S undergoing transformation to a period correct, Sports Purpose coupe in Italy, using mostly NOS parts.  Details of this project are:

Webers modified for use on a 2.5 liter, high compression, twin-plug engine with Mod-S camshafts and 911R intake manifolds:

Level 3 Service

Intake manifolds restored

Throttle bores enlarged to 44mm

Progression circuit design matched to 44mm throttle bores

Tall auxiliary venturis installed

Fuel well baffle plates installed and main fuel pick-ups relieved

Performance Profile throttle shafts

Tuneable idle air bleed jets

Tall aux venturis with modifications to secure from vibration damage

Tall (56mm high) intake air horns

Anti-percolation modification per second generation by Performance Oriented

Throttle lever arms are NOS 906/911R (shorter than production lever arms)

Emulsion tube well air screens

Black safety wire of OEM gauge and installed per OEM tying method

Tall M5 nylock nuts restored and reused (good, serviceable, NLA nuts sourced and reserved from previous projects)

The M4 split lock washers used for securing the hex nuts on the accelerator pump covers are OEM, heavy cross-section and have the serrations on the faces in contact with the nuts and the top covers.  Good, serviceable, NLA washers sourced and reserved from previous projects.

All studs are of the earlier versions used on Webers with machine-cut threads and radiused ends

I recently provided restoration services for two sets of original 46IDA3C Webers from two different 911Rs; these were for cars #11 and #19.  I used this opportunity to document the subtle differences between these race application Webers and those used on production 911s. 

The engines for the 911Rs were essentially the same as for the first 906s (904s with 6 cylinder engines dating from 1963) and later the Carrera 6s (906 designation again).  In round numbers there were 60 six cylinder race engines mated with either 904/6 or 906 chassis; it then makes sense that Porsche would purchase a convenient quantity of carburetors to fulfill the production requirements along with sufficient spares.  I assume a buy quantity of 75 to 100 sets as a reasonable guess.  The Webers I serviced all had one or two digit serial numbers, the highest number being #46.

MFI Throttle Housings and Intake Stacks as typical for 1969 through 1971 model years.  Complete restoration including:

-bored and new throttle plates

-new journals; extend full length of available housing

-shimmed throttle shafts to control end-float

-new 8mm ball studs on lever arms

-new 8mm ball sockets

-bench-set for air flow and throttle stop screws

-OEM magnesium chromate finish applied after machine work

Pair of tall MFI throttle bodies from a 1986 911SCRS.  The OEM magnesium chromate finish was restored to after machining to preserve the raw magnesium finish resulting from machine work.