 One of the initial batch became the experimental Cosworth Mk.X in 1962.This was followed in 1963 by the dry-sump Mk.XII with racing camshafts designated the 'CPL2' (26/66/66/26) and high compression Cosworth pistons, used actively by Team Lotus in Lotus 20B, 22, 23 and 23B.The Mk.XII was developed into the Mk.XIII for Formula racing with the addition of a Cosworth 12-bolt forged steel crankshaft, Cosworth forged conrods, wilder camshafts and 45DCOE Weber carburetors.