Overview
2023 was the 903's first season of racing in the UK, twelve years after its last race in America, its first in the CALM All Porsche Trophy, and Kenn van Hauen's first as a racing driver. Reaching the grid had taken the best part of five years. Kenn van Hauen earned his Motorsport UK National B race licence at Castle Combe in February 2022, only for the engine to seize during a pre-season track day at Donington Park a month later. The full forensic rebuild by Russel Lewis at RSR Engineering that followed was not completed until February 2023.
The car raced on the Paxton supercharger inherited from its American racing days, running a 3.5" pulley for the first half of the season. A 3.25" pulley was fitted between Anglesey and Brands Hatch, and with the remap by Dave Rowe at EPS that the extra boost required, it produced 306bhp in race trim. The car also carries the Snow Performance water/methanol injection system from its American days, which lifted the output to 321bhp, but injecting water or methanol into the intake is not permitted within 750 Motor Club racing, so on track the system is switched off and the engine runs an alternative map. No intercooler was fitted, as the Paxton could not sustain useful boost against the additional back-pressure of one. Entered in the Invitation Class, the 903 was the first 911 to race in the series.
This was a season of learning: finishing races, building mileage and experience, and working towards the international finale at Spa-Francorchamps. The results reflect that. The car started most races from the back of the grid, but the lap times came down steadily at every event.
Round 1: Donington Park National Circuit, 10th April 2023
The 903 did not take part in the season opener. Pre-season testing with the CALM All Porsche Trophy at Donington Park on 5th March had shown that the newly rebuilt engine needed an external oil breather and catch tank to cope with crankcase pressure and blow-by. While Phil Brough was carrying out that work, the front oil cooler let go on a start-up test, unable to take the pressure delivered by the uprated 996 Turbo oil pump fitted during the rebuild. It was a failure far better discovered in the workshop than on track, but ordering and fitting a new Mocal cooler cost the car the opening round. The new oil cooling and catch system was tested successfully at Snetterton on 18th April, clearing the way for Anglesey.
Round 2: Anglesey International Circuit, 13th & 14th May 2023
Anglesey was the 903's first race in the UK and Kenn van Hauen's first ever race, and the first time a 911 had raced in the CALM All Porsche Trophy. The official series report welcomed "an impressive 1973 LHD slope-front", and Autosport picked out the car in its National Novelties column. Saturday was sunny and dry, Sunday misty and damp. The 903 finished both 15-minute sprint races, 27th and 29th, bringing its best lap down to 1min54.98secs and taking second in the Invitation Class behind Richard Harman's 944 Turbo on each occasion. Contact in the first race had left the front right damper leaking, found by Phil Brough during the evening preparation, and although the car was judged safe for the second sprint, it was withdrawn from the 40-minute race as a precaution. The dampers were reconditioned by Ian Gardiner at I.G. Racing in time for Brands Hatch.
Round 3: Brands Hatch Grand Prix Circuit, 8th July 2023
Round 3 was an MSVR meeting on the Grand Prix circuit, with the CALM All Porsche Trophy sharing a 46-car grid with Bernie's V8s and Historic Outlaws in a single race, and the 903's first outing on the smaller 3.25" pulley. The weekend ended in qualifying, and three separate problems came together to end it. The car had been overfilled with oil, and the smoke that caused brought out the black flag, which is what the official report records. The clutch was slipping too, cured temporarily by Phil Brough pouring Coca-Cola into the clutch housing, the kind of race-day fix that comes from decades of paddock experience. What actually ended the weekend was a gear selection problem. Phil later found oil throughout the bell housing with the clutch plate contaminated, and at the time the oil and the clutch were connected to one another. Only later in the season was the real source identified: the 915 gearbox main shaft seal and its o-ring, leaking gearbox oil into the bell housing.
Round 4: Snetterton 300 Circuit, 12th & 13th August 2023
Snetterton was the first weekend the 903 completed in full: qualifying and two 15-minute sprint races on the Saturday, and a 40-minute race with a compulsory pit stop on the Sunday. From 29th on the grid after a 2mins41.90secs in qualifying, the car finished all three races, 27th, 25th and 22nd, and its lap time fell every time out, to 2mins38.50secs, 2mins37.66secs and finally 2mins35.67secs in the 40-minute race. It won the Invitation Class in all three, and Kenn van Hauen's daughters presented the awards for the weekend.
Round 5: Circuit de Spa-Francorchamps, 6th to 8th October 2023
The season ended at Spa-Francorchamps, where the CALM All Porsche Trophy joined the All Dutch Porsche Club Racing for its SuperSpa weekend. Racing abroad meant meeting FIA rather than Motorsport UK fuel tank regulations, so an 80-litre ATL FIA tank was fitted in place of the foam-filled aluminium tank, along with Yokohama Advan A052 tyres for the rain that October at Spa all but guarantees, and front lights for a race running into the early evening. In the event it stayed dry and sunny all weekend.
After a day of practice, the 903 qualified among 51 cars with a 3min18.045secs, four seconds quicker than on the Friday. Sunday brought two 1-hour races, each with a mandatory 2-minute pit stop, and the first began badly: a misaligned mirror and an unfastened seatbelt on the formation lap meant a trip into the pits at the end of lap 1 to put things right. The rest of the race still produced a 3min17.983secs. The second race opened with 15 minutes behind yellow flags after a heavy first-lap incident at Fagnes, and once the green flag came out the 903 set its best lap of the weekend, 3min16.439secs, a further one and a half seconds quicker. The car ran fault-free through both races, and with several cars in its class failing to finish, the weekend ended with a runner-up trophy.