Initially the cars were fitted with the 2 - litre powerplant .
As Climax gradually stretched the FPF 's capacity the Lotus 16 appeared with a 2.2 , then finally a 2.5 - litre , full Formula One engine specification .
Initially the cars were fitted with the 2 - litre powerplant , but as Climax gradually stretched the FPF 's capacity the Lotus 16 appeared with a 2.2 , then finally a 2.5 - litre , full Formula One engine specification .