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  Porsche 935/78 'Moby Dick'
 

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Country of origin:Germany
Produced in:1978
Numbers built:Two (one never raced)
Internal name:930
Predecessor:Porsche 935/77 'Works'
Author:Wouter Melissen
Last updated:December 19, 2014
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Click here to download printer friendly versionEven though the various variants of the Porsche 935 were out decimating the opposition in the Group 5 class, Porsche's engineers at Weissach continued the development work. For the 1978 the Norbert Singer led team produced the most extreme 911-based racing car yet. While still built to the Group 5 regulations, it was also developed for a potential outright win at Le Mans against bespoke prototype racers.

The first order of business was a thorough redesign of the engine. The Porsche 911 Turbo based, air-cooled flat 6 was already pushed beyond its limits, resulting in reliability issues. For homologation purposes, the crankcase, crankshaft and cylinders could not be changed. Instead the attention focused on the cylinder heads, where there was plenty of room for modifications. The original air-cooled, single overhead camshaft heads were replaced by all new water-cooled heads that sported twin camshafts for each bank of cylinder. These were originally developed for twin-cam variant of the Porsche 908 engine back in 1970 and were also fitted to the latest version of the successful 936 prototype racer.

The departure of the traditional air-cooled heads was prompted by the use of the twin overhead camshafts. There was no other way to cool the spark-plugs, which were no longer mounted in the air-flow but nestled between the two camshafts. What remained was a separate head for each cylinder. These sported four valves per cylinder for optimal breathing. Ultimately limited by the crankshaft design, the engine displaced just over 3.2 litre. Thanks to the more consistent method of cooling, the compression ratio could be lifted to 7.0:1 from 6.5:1 on the earlier engines. Running at a reliable turbo-pressure of 1.5 bar the engine officially produced 750 bhp at 8200 rpm. For qualifying the boost could be upped to 1.7 bar, which was enough to force 845 bhp out of the six cylinder engine.

Meanwhile Singer had had another good look at the regulations before he started construction of the chassis. He took a standard 911 Turbo shell and cut off everything fore and aft of the cockpit, leaving the bare minimum required for the homologation. On both ends aluminium subframes were grafted to support the suspension and drivetrain. For 1977 the FIA had changed the rules to allow BMW to raise the floor of their front-engined 320i to make room for a bigger exhaust system. Singer exploited this loophole and raised the floor on the new 935 as well. While at it, he replaced the steel floor he cut out with a much lighter fibreglass copy. There obviously was no exhaust to route under the floor, instead Singer dropped the suspension, lowering the car by 75 mm without breaking the homologation requirements.

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  Article Image gallery (54) Chassis (2) Specifications User Comments (1)