page_title: Triumph slant-four engine
section_title: Sprint 16-valve engine
hierarchical_section_title: Triumph slant-four engine / Sprint 16-valve engine
caption_attribution_description: 1974 Triumph Dolomite Sprint
context_page_description: The Triumph slant-four is an inline four-cylinder petrol car engine developed by the Triumph Motor Company. It first appeared in 1968 in the Saab 99. The first Triumph model to use the engine did not appear until 1972. With an original capacity of 1.7 L, displacement grew over time to 2.0 L. Production ended in 1981.
context_section_description: Triumph added a unique 16-valve cylinder head to the slant-four for the 1973 Dolomite Sprint. At the time there were at British Leyland (BL) both Harry Mundy, who worked on engine development at Jaguar, and Walter Hassan, also at Jaguar but in charge of engine technology development at BL as well. These two shared data on four-valve cylinder heads with King. A team of engineers led by King developed a 4-valve-per-cylinder head where all of the valves are actuated by a single camshaft rather than the more conventional DOHC arrangement. The valves are arranged in two rows of eight, inclined 27° from vertical. The inlet valves are 1.38 in (35.05 mm) in diameter and are operated directly by the camshaft lobes through bucket tappets, while the exhaust valves are 1.21 in (30.73 mm) in diameter and are operated through bucket tappets via rocker arms. The design of the cylinder head won a British Design Council award in 1974.
  Capacity was increased to 1,998 cc (122 cu in), and larger HS6 SU carburettors were fitted. Other changes to the Sprint engine included a duplex timing chain and alloy timing cover. The big-end journals were also cross-drilled.
  King returned from holiday "to find an engine running on the bed giving 150 bhp at the first build." Unfortunately the production line was unable to reliably build engines to the same specifications, production engine outputs being in the region of 125 bhp (93 kW) to 130 bhp (97 kW). The final output target was thus set at 127 bhp (95 kW), short of the original target of 135 bhp (101 kW) but a significant increase over the smaller 1.85 L variant nonetheless. This reduction in output also led to the originally planned model designation of Dolomite 135 being replaced at short notice with the Sprint name.
  The Dolomite Sprint has been described as "the world's first mass-produced multi-valve car". Multi-valve engines had first appeared in 1912, with the most recent prior to the release of the Sprint engine being the Cosworth BDA (1969) and Lotus 907 (1972), but they had not been not used in mass-production vehicles until after the introduction of the Dolomite Sprint.
  The 16-valve 2.0 L engine was also used in a small number of prototype and pre-production TR7 Sprints built at Triumph's plant in Speke during 1977.
caption: Triumph Dolomite Sprint engine
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