The reason why Trintignant ran in the "F1" heat is because, although the F1 cars were the 4.5 litres un/sc and 1.5 litre sc'd cars of the still current formula, Trintignant ran a Type 23 6 cylinder engine that was to be used in the following season (1954). Because it was going to be F1, so he was allowed to start.
This engine was developed in 1952 and had been sneaked into a few events previously. As has always been suspected, this included the 1952 Grand Prix de la Marne where Jean Behra beat the factory Ferraris.
Even at this meeting there was a degree of shananigans going on with engines.
Schell retired from the F2 heat with a "sick" engine variously reported as "engine trouble" or "spark plugs".
Then it was claimed that although Trintignant finished 4th in his heat, his 2.5 engine was in poor condition at the finish and was going to be a non-starter. Then Maurice fronted for the final with the "sick" 2 litre engine from Schell's car installed, and proceeded to lap faster to finished 3rd.
Go figure?
I have checked Huet's excellent book on Gordini and that gives a different story, more likely to be true.
Trintignant practiced Mières' car No 34, and preferred it's handling to that of his own Chassis 32. The 2 litre engine in 34 broke and was taken out and repaired during the night. It was then replaced by the 6-2473 (T23) and 34 became Trintignant's car.
Mières was left with 32, which received engine T20-36 (the spare engine). It is unclear which engine was in there before (maybe the T23?)
Schell had car no 31 all the time with engine T20-35.
In the F2 heat Schell stopped after the first lap, with a badly running engine. Spark plugs were removed and one was badly oiled (Not the cause of the malfunctioning but a result, I would think). It was replaced and after one more lap, the car was retired. It was still classified 9th, 8 laps behind, in a ten lap race.
Trintignant finished the F1 heat with a distinct lack of oil. It had used 4 litres in 90 KM and oil pressure tended to drop away in the last lap(s?). That can easily have been overcome with a lot of fresh oil, and maybe some repairs where the oil was escaping the engine. It seems clear here that Trintignant used the T23 engine also in the final.
