 The first big breakthrough was the launch in October 1948 of their new record-breaking engine design in their XK120 sportscar to replace the prewar SS Jaguar 100.It was powered by a new twin overhead camshaft (DOHC) 3.5-litre hemi-head six-cylinder engine designed by William Heynes, Walter Hassan and Claude Baily.The XK100 4-cylinder 2-Litre version had broken records in Belgium travelling at 177 mph.