By the end of 1971 the Porsche 917 and Ferrari 512 battles were over and the 5.0 litre (‘big bangers’) had been replaced by a 3.0 litre formula for sports racing cars. Porsche now realised that the development of the 911 for GT racing and not just rallying, as it had been mainly used for previously, was becoming increasingly more urgent. For 1972, the Porsche racing department developed the 911S into a lightweight 2.5 litre Group 4 FIA GT racing car – the 911 S-R 2.5, or more commonly known today as the 911 2.5 ST.

In 1972, over an eight month period, the Porsche factory built just twenty-one of these special racing cars, which were offered to private teams to compete in Group 4 FIA events. The M491 option was a lightweight / full competition-prepared designation, similar in spec to the RS-R which came the following year and included the special features laid out below.

The 2.5 S-R was in fact the 1st FULL race-specified and fully homologated Group 4 car, which could be bought directly from the Porsche factory racing department (the 911-R not being homologated), which came with everything fitted as standard (the previous years T/R and ST’s being built from an option list) and set the pattern for the Factory Group 4 cars to follow, such as the RSR’s and 934’s, etc.

The new Type 911/70 race engine: Aluminium–alloy cylinders with an increased bore to 86.7mm and stroke increased from 66mm to 70.4mm to produce an increase in capacity to 2492cc. Built with racing pistons, the cylinder heads had polished intake and exhaust ports and larger valves, together with racing camshaft and racing exhaust system. Equipped with a twin-ignition system and Bosch racing mechanical injection system with high-butterfly intake. Power output was 270 bhp with 193 lbs. ft torque.

Transmission
The new 915 gear-box was fitted with an extra oil cooling pump, limited slip differential and competition shafts.

Body and Chassis
The lightweight chassis had extended front and rear wheel arches (front arches the same as the following year’s 2.8 RSR – with same part No – and the rears the same as the 1971 ST) to accommodate the fitment of 7 or 8 inch Fuchs racing wheels to the front, and 9 inch to the rear, as permitted by the rules. The suspension was lowered with A-arms to the front and semi-trailing arms at the rear and with uprated hydraulic shock-absorbers and a choice of anti roll bars. Brakes were also uprated to ventilated discs with a dual-circuit system and could be fitted with aluminium 908 “quick release” front calipers (magnesium was also offered as a werks option and fitted to #1195) and special aluminium rear calipers with racing-pads and brake-fluid.

An aluminium engine lid and rear panel with the deletion of badges was fitted, fibreglass hood and lightweight doors. A long-range plastic 110 ltr fuel tank was fitted plus a special large capacity race oil tank with twin larger bore front oil coolers, both unique to the 2.5 S-R.

The bodywork was lightened further by the deletion of all sound deadening and interior trim, which was mainly covered in black felt. A roll-hoop and either Recaro or Scheel racing buckets seats were installed (seat make preference was no cost option) and racing harness seat belts. The steering wheel was 380mm, padded and leather covered.
A 10,000 rpm tacho was fitted inside the dashboard, together with twin-ignition coil cut-offs below, Bosch battery isolation switches inside and out and a fire extinguisher system.

Chassis # 911 230 1195
One of the original twenty-one genuine factory built (M491) Porsche 911 2.5 SR built by Porsche in 1972. 

Chassis no. 911 230 1195 (M491) race specification.
Engine Type 911/70 no: 662 20 39
Gearbox Type 915 (5-speed) no: 712 00 26
Finished in Light Yellow (117)
Green tinted glass (M568)

The car was delivered new in April 1972, via MAHAG in Munich to the well-known Bavarian driver Anton (Toni) Fischhaber.

Fischhaber competed successfully in motorsport between 1959-1987, taking at least 200 victories in mountain hill climbs and at race-tracks; as a Porsche works driver he was team-mates with Gerhard Mitter and while at Abarth, with Hans Hermann. Fischhaber entered this car, when brand-new, into the 1972 European Hill Climb Championship. The Championship included ten races, held in France, Austria, Germany, Switzerland, Italy and Spain. Having previously won the same championship in 1967 in a 2.0 911S, Fischhaber won his second international title in this car in 1972. Additionally, in 1972, Fischhaber entered the biggest and what was considered at the time, the most important race in Germany, the 1000kms race at Nürburgring. Together with Prince Leopold Von Bayern, Fischhaber came 14th Overall.
In 1973, he defended the championship yet was unable to win that year, although he finished 14th overall, once again with Prince Von Bayern, in the 1000kms race at the Nürburgring.

However, 1974 brought triumph once more and Fischhaber won his third European Hill Climb Championship title – for the second time in this car.

During those three years, in order to remain competitive the car was uprated for the 1973 season to 2.8 ltr capacity, wider wheels and a ducktail rear spoiler and again to 3.0 capacity for 1974.

At the end of the 1974 season Anton Fischhaber placed an advert in the magazine ‘Powerslide’ in order to sell the car. # 911 230 1195 found a new home in Switzerland. Stored for many years, in 2008/9 the car was sold via Elevenparts in Switzerland, by Peter Heuri to the UK, into one of the most significant Porsche collections. Still wearing its RSR bodywork modifications, none-the-less the car / chassis remained unrestored and extremely original –