Weber Carburetors and the 911

The last production year for Porsche cars using the Weber 40IDA3C type carburetor was 1972.   The ongoing requirement to improve fuel efficiency and decrease engine emissions (which was better achieved by use of EFI systems) heralded the end of carburetors on Porsche engines.  The only remaining manufacturers using the triple throat Webers were Ferrari for the 365 GT/4BB & BB512, Lamborghini for the Miura P400, Matra for the Alpine A310 V6 and the Talbot Tagora V6.  This shift resulted in the decline in total demand for triple throat Weber carburetors leaving an aftermarket demand for those wanting to replace fuel injection fuel delivery systems with the simpler Weber setup.  Weber (Bologna, Italy) then focused their interests on manufacturing fuel injection components and after acquiring the Carter Carburetor Company in Sanford, North Carolina (acquired by Weber for the purpose of entering the American auto market with fuel injection components) the production of triple throat Webers was transferred there in 1979.  This continuation of production continued through the early 1990s.

According to Karl Ludvigsen, Ferdinand Piech requested Weber to create a triple throat carburetor design to replace the Solex 40PI carburetors developed for the early production 911 and to use that design as a basis for a racing version capable of receiving larger venturis than the Solex design could accommodate. The first application for this triple throat Weber design was in support of the 6-cylinder Porsche 901/20 racing engine.  Six 904 GTS race prototypes (906 and not 904/6) were outfitted with this engine in 1963.    Carburetor testing using two of these 906s was conducted at Monza in December 1964; one used Weber 46IDA3C carburetors with 46mm throttle bores and the other used Solex 40PI carburetors with their throttle bores increased to 44mm with the 46mmWebers being selected for competition use. 

For the production version of the 901, Porsche developed the type 821, six-cylinder engine which incorporated Solex carburetors, the typical manufacturer selected for providing carburetors for their production engines.  These Solexes were specifically redesigned for the type 901/01 engine (becoming the Solex type 40PI); three being mounted on a common intake manifold with a single, integral fuel float bowl; two sets per engine.  The first production 901 cars (later renamed 911) were introduced in 1964 and used the 40PI carburetors but Porsche later abandoned the 40PI due to their short service-life and associated tuning issues; their replacement with Webers started in Feb 1966 and continued until replacement with MFI and later CIS fuel delivery systems. 

Prior to Porsche adopting them for use on the 911 in 1966, Webers were only used on their dedicated racers beginning with the 550 Spyder and continuing with use on prototype and GT racers through the early 1970s.  Their development for the 906 engines in 1964 explains how Webers were readily available for the production 911 in February 1966 after the Solexes proved troublesome in service.

It is interesting to note that Weber did produce a series of triple throat carburetors used by the Ferrari "Sharknose" 156 F1 cars of 1961 which were 40IF3C, but these carburetors used a dedicated float bowl for each throttle bore while the Porsche triple throat Webers used only two bowls for the three barrels.  Also of interest is the claim that the 40IDA3C Webers were first used on the Lancia Aurelia V6 in the mid-1950s but that engine used either three twin-throat Webers or a single Weber carburetor feeding all six cylinders.

In service for decades, the Weber 40IDA3C carburetor has provided exceptional performance for six-cylinder Porsches, Ferrari BBs, Lamborghini Miuras (debuted as a rolling chassis at the Turin Salon in December 1965), Renault Alpine A310s, Chevrolet Corvairs, three-cylinder Saabs and for other applications. Demand for these carburetors remains strong as enthusiasts choose to replace their CIS or MFI equipped engines with the less complicated Webers.  However, the use of these triple throat Weber carburetors is dependent upon their being in excellent condition mechanically and then well matched for their intended application.  No longer manufactured in Italy, these carburetors are typically at the end of their service life and are scarce to find in decent condition. Fortunately, they may be resurrected by careful remanufacturing and tuning to provide performance and reliability equal to or exceeding that of new carburetors.

There were triple throat carburetors built using the original Weber tooling in Sanford, North Carolina.  This occurred beginning in early 1990 after the Carter Carburetor Corporation was acquired by Weber for the purpose of entering the American auto market with fuel injection components.  Since demand for aftermarket triple throat carburetors was predominately in the USA it was considered a good location to manufacture the triple throat carbs at that facility.  The product continued production through the mid-1990s but quality control was poor resulting in many being scrapped.  Not all these carburetors proved faulty, and many are still in use. 

The Italian triple throat Webers have “BREVETTATTO” with a big “E W“ and “MADE IN ITALY” if they were manufactured in Bologna, Italy or simply  have a big “W” with “WEBER” and “ITALY” if manufactured at an alternate facility in Italy, there being precious few of these.  Those produced in Sanford, North Carolina just have a big “W” and “WEBER”.

As an alternative to Webers, PMO carburetors were developed by Richard Parr (originally Porsche Mail Order which was changed to PMO after Porsche objected to the use of their name) and became available starting in 1997; they fill the void of new carburetors and provide design improvements for enhanced performance.  PMOs are excellent products but they are not Webers.  Webers enjoy a long and rich history and demand respect as such.  Cars originally equipped with them must retain them for originality, other enthusiasts prefer the pedigree or appearance of Webers over that of PMOs; and as good as PMOs are the Webers are excellent performers if in good condition.

Zenith triple-throat 40TIN carburetors as used on the 1970 and 1971 911T engines and the earliest Solex 40PI carburetors with their recirculating overflow fuel systems as used on the 1964 through 1966 engines have seen interest in applications on the 911 engines either from originality for the early cars or for lower initial cost in the case of the Zeniths.  All carburetors differ in individual details, however; they all share basic similarities and regardless of design variations they will all provide a multitude of poor engine performance troubles due to incorrect tuning, worn-out components and due to jetting errors.

Although the triple throat 40IDA3C type throttle body appears complex it is really nothing more than three separate single throat carburetors and two fuel float chambers combined into one housing or throttle body.  Each throat incorporates discrete fuel delivery systems to provide for all ranges of engine operation.

The most typical complaint about Webers is that they are finicky: this is true if they are old (defying adjustment due to wear issues) or are not adjusted properly (a surprisingly large percentage).  Fortunately, re-manufacturing by competent service providers can return Webers to their original operational excellence.  Certainly, PMO carburetors, mechanical fuel injection or electronic fuel injection systems have attraction over worn-out Webers for convenience or performance; choose your poison and embrace the challenges and uniqueness of your fuel delivery system selection: an enthusiast’s car has personality associated with its intrinsic demands.

There is little argument of Weber carburetors deserving their reputation as the finest high-performance carburetor available, grateful thanks to Eduardo Weber. 

Weber forever!