911 S Carburetor Mystery,long

[aturboman]

I have had a set of 911 Weber carbs and manifolds for many years now that are a bit of a mystery. I bought them from a guy who claimed they came from a early 911S and he had had them in storage for 15 years. When I first looked at them 10 years back I noticed they were 40IDAs and not 40IDS so I assumed they were just a good set and boxed them up. Ten years later I took them out today and started finding some interesting things. The manifolds are magnesium and are date stamped 67 but have 36mm bases, and clearly have never been ported. The manifolds also have vaccum 2 large ports on both sides and have a large check valve. The bell crank on the manifold also has some iteresting linkage. These appear to be sportomatic manifolds from my memory. The carbs are "67" also and have all the correct jetting for an "S" model. The have a small vaccum port on the bottom of each that is not present on other 40IDAs I've seen. Could these be from a 67 or 68 S engine with a Sportomatic? I believe the sporto was optional on the S, but does any one know if they used IDA or IDS carbs. They are in very nice condition, since they've been boxed for over 25 years now. Help.

[mjmoran]

They appear to a set of 68 "US spec" manifolds. My 68L has the same vacuum ports and an extra ball type on the linkage for the airpump? As far as them being Magnesium...I don't know. How can you tell?

[aturboman]

The biggest question is are they for a 68 Euro "S" sportomatic. The ports on the manifolds are too big for standard 911 and the carb jetting is all "S"
I checked the PET and there is a Sportomatic manifold number for 68 "S'. I was hoping someone form the board actually owns one of these cars and can shed some more light. Any "S" experts listning. Thanks for your input.

[mjmoran]

hmmm...got me there. Although the ports, size and stack height on my 67S and 68L are the same. The only difference is that the manifold on the 68 has the vacuum ports and spare linkage. I had never thought about the sporto part for the vacuum area though. BD in So Cal has a 68L sporto...maybe contact him???

[B D]

The manifolds look like exactly like what’s on my car. I don't think there was a "S" specific manifold for the Sporto in 68. The number you found is most likely the same for a 911L, not sure about a standard 911. I will check my spare parts catalog.

"The have a small vacuum port on the bottom of each that is not present on other 40IDAs I've seen."

As for vacuum ports on the carbs that was not part of the Sporto system. Would be interested to find out what they could be used for?

[ValveFloat]

The IDAs on my L each have a vacuum port for the vacuum advance/retard? on the distributor.
The extra linkage is for a decel device that holds the throttle open slightly when there is high vacuum, ie when engine brakeing. IIRC, the larger vacuum ports on the manifold are for this device. I just learned about this device when I recently purchased an orginal owner's manual, as it was removed from my car before I took ownership.

[mjmoran]

Thanks Brett for chiming in here...I had always thought they were for the sporto...guess not.

Joe, that is interesting info...I have not seen a vacuum advance dist. on a 68 before( mine is all original minus the air pump and the distributor is a cent advance like a 67). I do know that 68 was an odd year for emisions and there were LOTs of new not very friendly devices used to make the cars clear the strict EPA laws. I will have to look for the reference you site in my drivers manuels...

Cheers,

[aturboman]

According to my book the Sporto intake manifold for -68 T & L is P/N 905 108 031 01. The number for Sporto -68 S models is 905 108 031 03. This is in the Euro parts book not the US book. Porsche wouldn't use a manifold with 36mm ports on a standard engine with 32mm intake ports, would they? This is is the mystery, they clearly aren't ported but cast with the larger openings on the bottom.

[Eric911S]

Hello: All of the stock Porsche Weber manifolds are magnesium. The ports are machined then coated with the black coating. I machine the bore of the manifolds so you can't tell them from factory. You have to remember that Porsche did lots of odd things back then. I bought a 69 E that had S MFI stacks and heads on it. Porsche would sometimes build up cars from parts they had to fill the orders. You may have something like that. Thanks Eric

[aturboman]

Eric, Porsche did have reputation for mixing late and early equipment in the past, something I've run into on early restorations before. I quess I'll have to assume that these "S" spec parts were on a 68 sportomatic at one time or another. Weather the car was actually an "S" model or not I guess I'll never know. Thanks for you input.