Editing Vauxhall Slant-4 engine (section)

==Vauxhall 16-valve engines==
After experimenting with an 8-valve twin cam cylinder head, Vauxhall began development of a 16-valve, twin cam head for the Slant-4 in the early 1970s. The first test engine, 'Old Number 1', was running by 1973. The cylinder head was similar to the Lotus head in principle, but different in detail; in particular the cam carriers on the Vauxhall engine were angled upwards so that the covers were both horizontal (those on the Lotus engine were equal about the cylinder centreline).

The 16-valve was announced for use in the [[Vauxhall Chevette#Chevette HS|Chevette 2300 HS]], which was immediately homologated for racing by the RAC MSA. Vauxhall's own 16-valve head had passed beyond the design stage, but initially was in such short supply that the rally team continued to use the Lotus heads.<ref name="coomberbook"/>{{rp|248}} To address the production shortfall Vauxhall approached [[Cosworth]] and had them produce the 400 cylinder heads needed for the racing homologation requirements.<ref name="cosworthbook"/>{{rp|83, 84}} When the new Vauxhall heads appeared in the Chevette 2300 HST the other teams complained, which led to a homologation scandal. This in turn led to the cars being prevented from starting the 1978 [[Rally de Portugal|Rally of Portugal]]. As a result, all cars competing in international rallies were forced to use the Vauxhall head.