The original Lotus twincam (as in this example) were 1558cc, based on a 5 bearing Ford block, and capable up to about 1700cc in an advanced state of tune. The later Lotus twin cam, based on a Vauxhall/GM block, was 2 litre capacity.
Dunno about the car from those pictures. Only a handful of genuine Lotus S3 had a factory fitted twincam.