The Nissan S20 engine was a straight-6 four-valve DOHC internal combustion engine produced by Nissan from 1969 to 1973, originally designed by engineers of the former Prince. It was the first mass-produced Japanese engines with more than two valves per cylinder. Essentially a revised production variant of the 1966 Prince GR-8 engine from Prince/Nissan's R380 racecar, it produces at 7000 rpm and of torque at 5600 rpm and weighs . The S20 powered Nissan's Skyline GT-R (C10 and C110) and Fairlady Z432 models. This engine is not to be confused with the unrelated SR20 (consisting of the SR20Di, SR20DE, SR20DET, SR20VE, and SR20VET engines), which were straight-4 DOHC petrol engines from the SR series used in other Nissan models. History The S20 was one of the technical carryovers to the Nissan brand from Prince technology. Prince had been producing the Skyline since the model's inception in the 1950s; following the merger of the two companies, Nissan took over production of the Skyline, which received the new engine in the late 1960s. The third generation Skyline was exhibited at the 1968 Tokyo Motor Show in October, which included a special "Skyline 2000GT Racing" model equipped with the S20; it was promoted as being equipped with the same engine as the R380. The production Skyline 2000GT-R (chassis code PGC10 for the four-door saloon) was introduced in February 1969, followed by the Skyline Hardtop 2000GT-R coupe (chassis code KPGC10, with a shortened wheelbase and 2 fewer doors) in 1970. The two models (PGC10/KPGC10) would later collectively win 49 straight Japan touring car victories between 1969 and 1971. Aside from its use in the PGC10/KPGC10 Skylines, the S20 also was fitted to the Nissan Fairlady Z432, a sports racing model of the Nissan Fairlady Z (S30) line, starting in fall 1969. The Z432 designation was derived from the design of the S20: four valves per cylinder, three carburetors, and two overhead camshafts. In addition to the S20, changes in the Z432 version included a 5-speed manual transmission and a limited-slip differential. A special lightened variant was designated Z432R. The cost of the Z432 was nearly double the price of a standard Fairlady Z. In September 1972, Nissan introduced the fourth generation Skyline (chassis code C110) powered by the L series of engines. A KPGC110 "Skyline 2000GT-R Racing Concept" powered by the S20 was shown at the 1972 Tokyo Motor Show after the commercial models