www.QV500.com - Porsche 911 (1970 - 71) Part 3: 911 2.3 & 2.4 ST/GT
 
In addition to the ST/Rally, 1970 also saw Porsche introduce a new 911 racing car. It too would take advantage of the 2.2-litre engine and replaced the T/R that been in limited production since 1968. More akin to the experimental R's than any other 911, the ST/GT was permitted to run an oversize engine for racing in Group 4, the FIA allowing Porsche to increase bore but not stroke. As a result, displacement was up to 2247cc, bore having been stretched by 1mm (to 85mm), stroke remaining unchanged at 66mm. Designated Typ 911/20, the highly tuned engines were equipped with twin-plug heads, camshafts from the Carrera 6 and special Mahle pistons.
   

There were also Biral cylinders, high compression ratios (10.3:1) and polished connecting rods, the Bosch fuel injection featuring butterfly throttle bodies and plastic intake trumpets. All told, this equated to 240bhp at 7800rpm. Track was widened by two inches and wider wheels fitted (7 and 9-inches front/rear respectively). There was no soundproofing or undersealing, a front-end brace being installed for extra stiffness. Lightweight steel shells were fitted with alloy doors, the front and rear lids, bumpers and wheelarches coming in ultra-thin glassfibre. The wheelarches themselves were considerably wider and gave the GT an especially purposeful stance. Perspex was used for the side and rear windows whilst the windscreen was still glass albeit again much thinner than before. Inside, the cockpit was gutted of almost every conceivable fixture (right down to the glovebox door and ashtray). A pair of Recaro sports seats were installed and overall, weight was cut to just 840kg. Fuel tanks could be specified in a variety of sizes. Three works cars were built for 1970 with chassis numbers 911 030 001, 911 030 002 and 911 030 003, a further 15 or so customer cars being completed.

For 1971, Porsche would be allowed to further increase displacement from 2.3 to 2.4-litres. In preparation, an experimental version surfaced for the non-championship Tour de France in September 1970. Built on chassis 911 030 949, this car had been developed over the summer for factory driver Gerard Larrousse. He famously offered the factory mechanics a case of champagne for every kilogram of weight they could remove below 800kg, but this wasn't going to be easy as the regular GT was 840kg. The whole package was drilled for lightness, extensive use of titanium and super light glassfibre panels meaning it eventually weighed in at 789kg. An experimental 2395cc Typ 911/21 engine was installed, this having been stroked from 66 to 70.4mm. Equipped with a magnesium block and three huge twin choke Weber carbs, Larrousse went into the race with 260bhp at 8000rpm and finished third overall. A sister car was completed on chassis 911 030 950. Customer cars for 1971 also used 2.4-litre engines but these were enlarged versions of the previous years 2247cc unit. Bored out to 87.5mm for 2381cc, output was 250bhp at 7800rpm, around a dozen customer cars being made.