917/10 Throttle Bodies

(not for sale)

Recently we received some well worn throttles from a factory 1972 917/10 car. The client's instructions were to restore them functionally, but with no attention given to appearance. No plating, no black coating on the throttle housings.

Recall that the 917/10 was Porsche's answer to the Lolas and McLarens which were dominating the Can-Am series at that time.  The 917/10 used a turbocharged 12-cylinder 5 liter engine which was capable of producing  between 800 and 1000 horsepower. Fewer than 20 of these cars were built and probably 12 exist today. 

These are the throttles as received:

Rather than developed an all new throttle for a small number of engines, Porsche used what was already being produced in large quantities for their 911 street car. Note the casting number: 911 110 101 1R

These housings started life as a second series 2.2E casting from 1971.  The only modification that was done to the throttle housing in order to change them from 911E throttles to 917/10 throttles is an increase in bore size.

With forced induction no taper is needed. Bores are 40mm straight through. Note the small groove on the side of the bore from contact with the throttle plate.

Removed rolled-steel bushings.  New brass bushings ready to install.

All hardware shown.  Levers are different than street MFI as well as two shafts (pictured on left) which are longer than normal to accommodate throttle linkage.

One of the housings was a Sportomatic housing.  Note the two vacuum ports which are shown blocked off compared to the non Sporto housing with no vacuum ports.

The Sportomatic housing also had its air bleed holes buggered, including compression of the seats from over tightening the incorrect screws.  The Sporto was damaged, and likely a replacement for the original housing.  After confirming with the client that the vacuum ports are not being used for pressure measurement or other reasons, and because of the damage to air bleed holes and seats, we decided to swap out the Sporto housing for a non Sporto.  Fortunately these are readily available.

New bushing installed. Small overbore....no more groove.

Bore is smooth.  New throttle plates machined to fit the new bore. Shafts were re-blued to help prevent surface corrosion after polishing. 

917/10 throttles all finished.  Balanced on a flow bench.  All 12 air screws 5 half turns out +/-  1/4 turn. Target idle of about 1600rpm.  Ready for Rennsport!

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