Pedigree of the LZ: The twin-cam engine that delivered a string of Nissan race & rally victories

Starring in the Japan GP, Safari Rally, and Super Silhouette Championship, the LZ was the motor sports engine behind Nissan’s formidable performance during the years when it had no twin-cam engine.

The LZ engine made its debut in the 1973 Japan GP (Fuji).

Good news - just in time to exact revenge
Designed for motor sports use, the LZ engine was a DOHC 4-valve engine that played a major role in races and rallies, both in Japan and overseas, during the period 1973-1983. The two letters "LZ" refer, respectively, to the L formation of the 4 cylinders and to the addition of a DOHC 4-valve head to what was originally a single-cam engine.
Of the three versions of the LZ engine - LZ14, LZ18, and LZ20B - the 1.6-liter LZ14 was the first to be developed. This engine powered the Sunny Excellent (KPB110) that won the Japan GP in 1973. And there is an interesting tale behind its development.
The story starts a year earlier, at the 1972 Japan GP. Nissan entered the Skyline GT-R and Sunny Excellent in this, the most popular touring car race. However, the GT-R (TS-b Class) was bettered by Mazda Savanna RX-3, while the Excellent (TS-a Class) was beaten by the combined forces of the Toyota Celica / Corolla Levin. It was an ignominious defeat for Nissan. The sudden ascent of the rotary-engine machines gave Nissan pause, and the GT-R was absent from the Japan GP in the following year.
This is why it was so important for Nissan that the Excellent should win. What had been planned for use in the 1973 Japan GP was the L14 (bored up to 1.6 liters), prepared to EGI specifications. However, with a single cam, the most output that could be expected was 180PS. There was thus no guarantee that it could beat the twin-cam Celica 1600GT, or the Corolla Levin / Sprinter Trueno.
Then in June 1972, the Vehicle Test Dept. engineers, who were searching for a solution to their engine problem, suddenly received some good news: from 1973 the FIA rules were to change and a DOHC head would be permitted as a bolt-on option. This was the answer! Adding a DOHC head would enable a considerable boost in power. This would give them a good chance of beating Toyota.
A project team was immediately formed and in September the plans were complete. It was a tight schedule, with the first prototype being tested in January 1973, and road tests planned for February. On February 28, JAF approval was obtained and they began to run the engine in properly at the Fuji Speedway.

The LZ head featured a narrow valve angle and shallow pent-roof combustion chamber.

LZ achieves debut win in ’73 Japan Grand Prix
Soon it was time for the 1973 Japan GP: May 3. The Nissan works team entered 9 Sunny Excellents equipped with the new LZ14 engine. The drivers were (1) K. Takahashi, (2) H. Kitano, (3) K. Tohira, (5) S. Suzuki, (6) S. Tsujimoto, (7) T. Teranishi, (8) T. Shinohara, (9) H. Yanagida, and (10) H. Kubota.
The race was dominated by Kitano in car No.2 (pole position, with a lead of 1 minute 31.17 seconds). Coming in 2nd and 3rd were also works Excellents. The LZ engine thus had managed a magnificent debut, taking the top three places with its unrivalled performance.
The LZ14 used in the 1973 Japan GP had a displacement of 1,598cc (bored up by 4.8mm to 87.8mm). Prepared to EGI specifications, maximum power was 200PS/9,400rpm, and maximum torque was 17.0kgm/6,800rpm. Instead of cast iron, the cylinder head was made from aluminum alloy, and the 16 intake and exhaust valves from titanium. It also featured a narrow valve angle of 34 degrees, an ideally shallow pent roof to the combustion chamber, and a compression ratio of 11.5~12.0. Each of the light-alloy pistons had a flat head with a deep valve recess, while the con rods were made from forged steel with mirror-ground edges. All the con rod/piston assemblies were carefully balanced to the same weight.
An innovative mechanism, using both gears and chains, was adopted to drive the camshaft: on the crank end was a 4-stage gear drive, while on the cam end there was a double roller chain. A special feature of the LZ engine was the thin housing for the cam drive. The head cover was rounded, unlike the flat type that was later used; it was finished with black crystal paint.
What made the development of the LZ engine special was the fact that, in a very short time, Nissan created a racing engine compact enough to fit into the engine room of a production vehicle, which offers little space, despite the fact that it had a narrow-angle valve layout (which tends to increase the overall height of an engine).

LZ20B

Major contender in overseas rallies
Later, owing to changes in race regulations, the LZ engine was mainly used for overseas rallies. The LZ18 was mounted in the Violet (710) and won the 1977 Southern Cross Rally in Australia. The LZ20B powered another Violet (A10) and dominated the Southern Cross Rally in 1979~1980 and the Safari Rally in 1981~1982. Prepared to rally specifications, the LZ18 (1,941cc) had a maximum power of 200PS/7,200rpm, while the LZ20B (1,952cc/1,975cc) generated 210~220PS/7,600rpm.
In Japan, at the 1978 Formula Pacific (FP1600) event that was started as a preparation for a Pan Pacific Championship, the LZ14 (1,598cc, over 225PS) made a long-awaited comeback, winning the 1978 JAF Grand Prix in Suzuka and the 1979 JAF Grand Prix in Fuji. In May 1978, it went on sale as an FP kit costing ¥2,040,000, available from Motorsport Supporting Office in Omori (now NISMO). No other domestic racing engine was as conspicuous as the LZ in so many arenas of automotive activity.
Bringing the history of the LZ engine to a glorious culmination was the LZ20B turbo (2,082cc). This engine was used in the Super Silhouette races (Group 5) from 1979 to 1983 and put out more power than F1 engines at that time: from the start its maximum output was 500PS, and this rose to 570PS (final specifications). The achievements of the mighty Nissan turbo machines - the Skyline (Masahiro Hasemi), Silvia (K. Hoshino), and Bluebird (H. Yanagida, ’80/’82 champion) - thrilled the Nissan fans at the races. And this track record paved the way for the later Group C cars that starred in All Japan Sports Prototype Championship Series (JSPC) endurance event.