Could the triple throat Webers have been designed for Porsche?

[1QuickS]

Yes, I know Paul Frere said the Weber 40IDA3C carbs were designed for Lancia Flaminia V6 dating from 1957. They were not used on them as they used three double barrel Webers or one Solex triple barrel Type C35 P3 1 2 carb. Possibly the design WAS developed for the Lancia Flaminia Super Sport Zagato (their top of the line, light weight performance offering) but wasn't incorporated for production since three double barrel carbs were more cost effective for the limited production volume of the Super Sport Zagato.

Vittorio Jano designed the 60 degree V6 engines which were used by Lancia and then this engine was revised to be 65 degrees for Ferrari. The V6 Ferraris (Dinos for sports racing, F2 and F1 of the late 1950s & early 1960s) typically used three double barrel Webers except for the 1961 F1 engine Type 156 used in the Shark Nose F1 car Phil Hill became world champion in. Those engines used Weber 40IF3C carbs with a float bowl per barrel and are definitely a different animal from what the 911s use.

The 901/20 competition engine was developed sometime around mid 1964. Two 904s were equipped with the 901/20 engine and taken to Monza in Dec1964 for testing; one used Solex 40PI carbs bored to 44mm and the other used 46IDA3C Webers.

Since Porsche turned to Weber for their competition engines and there were precious few manufacturers in that time frame with a V6 engine I am left with the conjecture the Weber design used on the 911 was available for the 911 but never used by other manufacturers prior to Porsche's use.

I talked with Mike Pierce of Pierce Manifolds and he was not able to shed light on this topic.

Curiously the 46mm throttle bore version seems to be a modification from a design that was probably a 40mm bore size. This is based upon typical carb design has a stepped counter-bore for the main venturi to seat into. A carburetor designed from a clean start to be 46mm would probably have an upper bore of 50mm and throttle plates of 46mm. This would also provide for better air flow through the carb. This leads me to opine the 40mm design pre-existed the 46mm design so when Porsche went to Weber for the 901/20 carburetors I think Weber took the design for the Lancia and bored it out to 46mm.

As for the close spacing of the barrels: economy of design. If spaced vertically above the bores on any engine of size there would be a lot of wasted space between the bores which is poor design for a production application.

Comments or insights?

Picture is of the 40IF3C Weber used on the Type 156 F1 Ferrari:

[37yrold911]

I don't think we will even know for sure without exhuming Eduardo

[Jon B]

The V6 Ferraris (Dinos for sports racing, F2 and F1 of the late 1950s & early 1960s) typically used three double barrel Webers except for the 1961 F1 engine Type 156 used in the Shark Nose F1 car Dan Gurney became world champion in. Those engines used Weber 40IF3C carbs with a float bowl per barrel and are definitely a different animal from what the 911s use.

Hi Paul,
No insight to offer on your carburetor question, just a reminder that it was Phil Hill who became World Champion for Ferrari, not Dan Gurney (who drove for Porsche at the time).



Jon B.
Vista, CA

[1QuickS]

I knew that! Just a senior moment, thanks for the schooling!

Original post corrected.

[304065]

Paul,

If you look at the earliest Weber installations (such as mine, on 304065, from April 1, 1966) the manifolds are sandcast magnesium with that strange oval shaped port on the ends, the crossbar is not reinforced, the welding on the crossbar is 917 style with big fillets, etc. All this smacks of a solution that was hastily pressed into service and later evolved with the flying buttresses on the manifolds, stiffening ridge in the crossbar with better welds, etc. If this was designed from scratch, wouldn't you think that it would have gone through those development turns before appearing in production? I don't KNOW any of this but I'm speculating. . . and genuinely interested in your opinion (you have the most informed opinions about carburetors in the world of Porsche today)

[1QuickS]

I think sand cast manifolds were the standard technique for manufacturing at that time and subsequent detail changes are typical design evolution. The engine case and transmission case were sand cast as were the intake manifolds for the Solexes. As time goes on the reality of faster production of higher quality parts with less wasted metal was realized using the permanent mold processes. I was thinking the sand cast manifolds were a quick solution while waiting for permanent molds to be made but forgot about the molds for making air cleaner housings. Definitely the making of permanent molds for intake manifolds and for air cleaners would both have a lengthy time-line. Solex manifolds were cast but the air cleaner housings were stamped from permanent molds.

It is clear Porsche was committed to Solex carbs for their production engines but the issues with Solex tuning & durability for the 911 forced Porsche to seek another solution. The 40IDA3Cs were readily available to use to "stop the pain" caused by the Solexes. Time did see the Solexes back on the 911s in the form of the Zenith 40TIN carbs for the 2.2 liter cars; those were a design development from the triple throat Webers but not without their own issues.

I doubt the origin of 40IDA3C Webers will be definitely determined and we will be left to "Happy Hour" discussions by early 911 nut cases like me. My position is that Weber developed the design for the Lancia Flaminia (Paul Frere's original comment which I do not take lightly as he was rather exacting in his technical writing and was VERY close to the source of info) but they were not brought into production. My research shows the Flaminia using single down draft, three double barrel Webers or two Solex C35 P3 1 2 carbs (Picture below; we could have been living with that!). Therefore, although the 40IDA3C design was not developed for the 911 it was available for use. A fortuitous match!

Curious question arises: Why did Porsche not use the Solex C35 P3 1 2 carbs if they were available from as early as 1957 and they had a preference for Solex on their production engines?????? Perhaps a "spat" between Porsche & Solex???? The 912s continued to use Solex carbs. I assume Porsche liked the "straight down" air flow into the cylinders three individual carbs could provide but quit Solex for the 911 project due to irritation with the Solex's performance?

[304065]

Paul,

As ever your perspective is well researched and rooted in facts. If things were then the way they are now, and reading between the lines of Frere, who said that " Porsche really tried hard to make things work with Solex" I can foresee it going down like this 50 years ago:

Solex is introduced on the 901/01 after prototype testing is successful
Holing pistons develops in the real world
Porsche tries to work it out

Solex is unable to deliver a solution that works
Porsche proposes to abandon Solex and develop Weber solution
Solex has focused discussion with Porsche about duration of relationship
Porsche executives are concerned for their own jobs and don't want to put them further at risk by trying to preserve Solex relationship
Weber is adopted
Bosch MFI is adapted from Diesel Tractors and offers +10HP and zero centrifugal effects
Hurt feelings are patched up and 911T comes out with Zeniths and all is forgiven

[1QuickS]

As good a summary as can be drawn without hard inside info.

[37yrold911]

Does Fiat Group have a corporate historian? If so, they may have inherited Weber documents when they bought Marelli/Weber.

[1QuickS]

GOOD suggestion! Another path to follow.