 The proliferation of the Mk.XIII triggered the establishment of new European style racing-engine builders in the US performing rebuilding and maintenance work needed on the Mk.XIII while also contributing to Cosworth's revenue.Other Cosworth engines based on the Lotus-Ford Twin Cam include the Mk.XV for the Lotus 26R and Lotus Cortina (almost all for Team Lotus and affiliated teams) and the Mk.XVI, a version of the Mk.XIII for the 1.5 Liter Class.Cosworth designed its own aluminium reverse-flow 2-valve gear-driven SOHC cylinder head for the same Ford 116E block.