The engine was switched to the 1296 cc version in April 1967, just one month after the Spitfire itself had undergone the same upgrade, the revised model being identified as the GT4S 1300. An increase in claimed output of 12% resulted. At the same time the front disc brakes were enlarged and the design of the rear suspension (one component not carried over unmodified from the Triumph Spitfire) received "attention".
