There was some logic in BRM's decision to construct a 16 cylinder engine for the new three litre regulations of 1966; double the size of the old regulations, double the cylinders. BRM's solution was a little less straightforward, and reminded of the overly complex and unsuccessful V16 engine used over a decade earlier. To keep the engine compact, the engineers placed two flat eights on top of each other creating an H16 powerplant. The engine looked good on the drawing boards, but proved too heavy and unreliable. One victory was scored by the engine, installed in a Lotus.
In 1967 BRM's Formula 1 effort was still focused on the H16 engine, but for the new 3 litre sports prototype class the British team started work on a less complex and expensive V12 engine. Late in 1967 the engine made its Formula 1 debut in the back of a McLaren. This opened BRM's eyes, and for 1968 the H16 was quietly set aside and replaced by the V12. Thanks to its much simpler design it proved to be a lot more reliable, although it was not quite as powerful as the 16 cylinder unit. Double overhead camshaft heads were fitted, but there were only 2 valves per cylinder, whereas most of the competition had already switched to four.
The first BRM equipped with the sports car V12 was dubbed P126. Designed and constructed by Len Terry, it was the first BRM chassis not built by the team. Three chassis were constructed by Terry, and equipped with the V12 engine and a Hewland gearbox, another first. The P126 was quite competitive, with a number of second place finishes in 1968 as the best result. Halfway through the season BRM constructed another two chassis to the P126 specification, but these were known as P133. One was quickly destroyed, but the other was raced with some success. Pedro Rodriguez crashed out of the 1968 Spanish Grand Prix while in the lead.
BRM finished fifth in the 1968 Constructor's Championship, which was quite an improvement over the dreadful 1966 and 1967 seasons. Just like ten years earlier, the return to simplicity proved to be the right tactic. For 1969 the P126/P133 was further developed and became the P138 and later P139. Another novelty was the introduction of a four valve head, but it was not enough to copy the relatively successful 1968 season.
Featured is one of the P126s on a rare outing in a historic race. It is seen here at the 2003 Nürburgring Old Timer Grand Prix.