Three Mazda RX-3s with the larger, racing 12A engine took part in the Japan Grand Prix in May 1972. They outpaced the Skylines and took all three top spots. The Racing 12A engine had a twin-choke Weber-type carburetor and generated 240bhp at 9000rpm.
After the race, the Nissan team lodged a complaint about Mazdafs bridge-ported engines. At the time, the race organizers decided to withhold judgment. However, this episode paved the way for a later decision to lift the ban on peripheral ports, under the condition that 50 units or more with peripheral ports were produced for motor sports.