This now gave Sakurai carte blanche to do whatever he wanted, and he set about building himself, with the help of his engineering team, what would basically be a Japanese Can-Am car. Under the previous regulations raced under in Japan all cars had to have a roof, and convertibles had to run with a hardtop in place. The first version he worked on was an evolution of the old R380-II. It was the same closed coupe design, but now with a revised rear section that incorporated a Kamm tail cut-off similar to that of the McLaren Can-Am car. The Group 7 regulations allowed for open top cars, but Sakurai continued with the coupe format.
All that changed abruptly when word got out that Toyota was starting work on their own Can-Am style Group 7 car, rather unimaginatively called the Toyota 7. And not only was the Toyota 7 a Can-Am style car, it was an open top as well. This caused Nissan to rethink their coupe design and late in it's design the roof section came off to make it an open top racer as well. No intergrated roll bar was included, all the car had for roll-over protection was a single tube behind the cabin.
In the Can-Am series Jim Hall had been experimenting with high-set rear wings on his Chaparral cars, and Sakurai decided to try these on the R381 as well. The novel wing arangement on the R381 consisted of a rear wing that was in two sections, with the left side being seperate to the right. These two wing sections were attached to hydraulic actuators that could change the angle of the wing. As the car went through corners one wing could stay flat while the other side tilted, this allowed the car to generate downforce only on the side of the car that required it in that corner. The film of the 1969 Japanese Grand Prix shows amazing images of the cars going through the esses at Fuji as the wings change position again and again through the corners.
If you are racing in a category that allows for an unlimited engine capacity there is no point playing aroung with 2 litre six cylinder engines, especially if you have a design team itching to seek out brave new ideas. And brave they were, because the engine they set out to build was a 6 litre V12. This was something way beyond anything they had attempted before, and full marks must be given for even attempting such an outrageous project, keeping in mind the fact that this was from a company that ten years ago could manage nothing better than a side valve four cylinder engine that produced 37hp. In the end they weren't able to get the V12 ready in time for the 1968 race, and panic set in. The car was ready, but they had no engine to put in it. Rather than give up, Sakurai decided to source an engine from another supplier as a stop-gap measure. Pride would stop him from approaching one of the rival Japanese manufacturers, plus none of them had an engine anywhere near powerful enough for what he had in mind. Sakurai decided to head for the home of Can-Am racing and went to the United States to look for an engine. Whilst there he was introduced to Dean Moon from Mooneyes, who offered to supply him an engine, or three to be precise. The engines he came back with were vastly different to the high-tech V12s he had planned the car around. Dean Moon provided him with three highly tuned and modified Chevrolet V8s, each engine was 5451cc in capacity and produced 450hp. This was well short of the 600hp he was hoping for from the Nissan V12, but still a massive jump in power over last year's 220hp 6 cylinder engines.
Even with 150hp less than hoped for the Chevrolet powered R381 had enough power to destroy the Toyota 7 with it's 300hp V8. But was it enough to beat the new Porsche 910 that was also entered in the 1968 Japanese Grand Prix ? Nissan entered three R381s in the race, there was also three of last year's R380-II cars, three Toyota 7s and several Porsches. At the end of the day a Nissan R381 wone the race, with a Porsche 910 coming second. Nissan also scored third, fourth, fifth and sixth places, while the best Toyota could manage was eighth. This was the first and last time Nissan would enter a factory prepared car with someone else's engine, and they now had a year to get the V12 sorted out. Next year's car would be the Nissan R382.
