the new model's "superpower" engine is enlarged 13 per cent achieved by lengthening its stroke by 14 mm. although the cubic capacity rose from 2810 cc to 3181 cc this did not affect the car's tax rating because the rac formula takes no account of an engine's stroke. the only other changes from the engine of the twenty 70 were the introduction of replaceable hardened steel valve seats and improved steel-backed main bearings for the crankshaft. the instrument panel now has a rheostat switch to vary the lighting at will.