In 1966 maximum engine capacity was significantly raised in Formula 1. The formula used since 1961 permitted no more than a tiny 1.5L displacement. Since that time sportscar technology had advanced to the point where they could easily outrun Formula 1 single seaters. A change had to be made, and so the maximum capacity was doubled to 3.0L.
The transition was not a particularly smooth one. The teams and more importantly engine manufacturers did not have adequate time to adapt to the new regulations. One such manufacturer was British Racing Motors, who had been running their 1.5L V8 in those years. As a temporary measure, the V8 was bored out several times, eventually reaching a maximum of 2.2L.
It was clear that the V8 had reached its limits, and a new unit had to be developed. BRM chose to tackle the issue in two key ways. On the one hand they would start developing an all-new 48 valve V12 in cooperation with specialist Harry Weslake, and on the other they would try to develop their 1.5L V8 into a radical new concept, the bonkers H16. They would then use whichever engine would turn out to be the best. As Weslake eventually bought BRM out of their agreement, BRM was left with the H16.
BRM started the process by effectively turning their 1.5L 16-valve V8 into a flat-8. It then placed another flat-8 on top of the first engine, and geared them together with a complicated system in the middle. This resulted in a layout that when viewed on its side resembled the letter H. However, the engine’s radical layout made it hopelessly complicated and very very heavy.
To even make the unit work, each side of the engine had to have its own radiator, fuel injection unit, distributor and water pump. To make matters worse, the complicated crankshaft assembly coupling the two separate flat-8’s together was prone to very harsh vibrations. Another unusual feature was the need for four separate exhausts leading from each of the four different cylinder heads. Because of this the engine had to be mounted much higher to allow room for the bottom pair of exhausts.
The engine’s complexity lead to a very high center of gravity, as well as a massive amount of weight. The first iteration of the P75 H16 weighed in at 251 kg (555 lbs). On a total car weight of 671 kg (1479 lbs) this was an incredible amount. Power was however favorable, at 395 horsepower at 10.250 rpm. A specially designed 6-speed gearbox then transferred the grunt to the massive rear wheels. Adequate power delivery proved to be problematic, as the H16 had a very narrow power band.
The monstrous power plant was eventually fitted to the new P83 chassis. It was mounted as a stressed member, a practice still very novel at the time. This concept would later be copied for the much more successful Ford-Cosworth DFV that would appear a year later. An aluminium monocoque was used, and suspension was very conventional for the time. Unremarkable as it was, the chassis was severely hampered by the heavy H16 unit, resulting in countless handling problems.
BRM’s drivers for 1966 were 1962 World Champion Graham Hill (GB) and young storming talent Jackie Stewart (GB). The P83’s debut came in practice for the 1966 Monaco Grand Prix. Stewart tested the car, but opted to run the older 2.2L P261 in the race, being uncomfortable with the new design. With the P261 car Stewart would score his second career win. Stewart didn't take kindly to the new car and especially the monstrous engine. He later commented:
Jackie Stewart, Mexico, 1966. Note the shortened nose used for increased cooling in the extremely hot conditions.
Further reliability problems with the engine’s unstable crankshafts (of which there were four) pushed the cars race debut further back. Balancing weights were hastily added to combat the issue, but the effort amounted to very little. The weights had the tendency to simply fly off and choose freedom, which lead to catastrophic engine failures. In response, the P83 was sidelined as work started to improve the H16 problem child.
After using the P261 for most of the season, Graham Hill and Jackie Stewart finally received the improved P83 for the final three races of 1966. First of the three was the Italian Grand Prix at Monza. BRM’s drivers only managed 9th (Stewart) and 11th (Hill) on the grid. The problems continued in full force however, with Hill forced to retire after less than a lap with a blown engine, and Stewart stopping on lap 5 after a leaking fuel tank had drenched him in highly volatile racing fuel.
The F1-circus then moved to the high-speed Watkins Glen track for the 1966 United States Grand Prix. The race’s organizers had promised the highest amount of prize money seen all season, so the struggling BRM was eager to finally score a good result. Jackie Stewart managed to put the P83 in 5th on the grid, closely tailed by Hill in 6th.
The cars completed a lot more laps this time, but were still out halfway through the race. Graham Hill had suffered a broken differential on lap 52, while Jackie Stewart’s H16 expired a lap after. Interestingly the race was won by Jim Clark in the Lotus 43 H16. Lotus had bought BRM’s engine as a stop-gap while waiting for the Ford-Cosworth DFV, and somehow made the maligned engine work long enough. The Lotus victory would be the H16's one and only win.
At the final round of 1966 in Mexico the P83’s again failed to finish. The cars had been leaking oil all weekend, with the problem turning out to be a broken oil pressure release valve. Having fixed the problem, BRM hoped for the best. Again, Graham Hill’s H16 was misfiring from the start, and lasted just 18 laps. Jackie Stewart made it to lap 26 before another oil leak drained and seized the engine.
Graham Hill was now rightfully fed up with the BRM’s many problems, and left for Lotus at the end of 1966. His replacement was the experienced Mike Spence (GB). Jackie Stewart opted to stay despite his reservations about the car.
History repeated itself at the first race of 1967 in South Africa. Stewart’s engine lasted just 2 laps, and Spence retired on lap 31 with an oil leak. At Monaco however he would give the P83 its first ever finish coming in 6th and last, 4 laps down from Denny Hulme in the Brabham BT20. Jackie Stewart this time had his differential give up on him. Spence would follow his amazing achievement up with 8th at Zandvoort, while Stewart again noted a DNF, this time with brake failure.
BRM had meanwhile been hard at work lightening the cumbersome H16 unit. Through some tricky engineering and packaging they managed to bring the weight down to 180 kg (398 lbs). Another new feature was the addition of four valves per cylinder, multiplying the total to 64 valves. Power had also improved, now at 420 horsepower. To counter the savage beatings the engine suffered from its own crankshaft assembly, a new two-pin design was fitted, greatly reducing vibrations.
The hard work definitely paid off, as Stewart scored 2nd place at Spa Francorchamps for the Belgian Grand Prix. Spence also improved, managing 5th. The P83 was now thoroughly on pace, as Stewart scored another podium with 3rd at the French Grand Prix run at Le Mans’ short Bugatti circuit. Spence suffered a broken driveshaft. A third car prepared for Chris Irwin (GB) made it to 5th.
The British Grand Prix at Silverstone proved to be the car’s last outing. The new and improved but still H16 powered P115 was waiting to be deployed. Chris Irwin this time finished best, scoring a 7th placing 3 laps down from winner Jim Clark in his Lotus-Ford. Jackie Stewart was the first to retire with a ruined transmission on lap 20, with Mike Spence ending up stationary on lap 44 with busted ignition.
The BRM P83 H16 was doomed from the start. The engine was way too ambitious and absurdly complex. Its massive weight, narrow power band and dreadful center of gravity in effect made it wholly unsuitable for racing. Its appalling reliability made its viability even worse. After stubbornly soldiering on with the concept in the P115, BRM eventually wised up. For 1968 it opted to developed a much more conventional and reliable V12.