In March 1945 the company name SS Cars Ltd was changed to Jaguar Cars Ltd.[2] All the Mark IVs were built on a separate chassis frame with suspension by semi-elliptic leaf springs on rigid axles front and rear.

Pre-war the car was available as a saloon or drophead coupé but post war only the closed model was made.

Performance was not a strong point but 70 mph (113 km/h) was possible: the car featured the same cabin dimensions and well-appointed interior as its longer-engined brothers.

Harry Weslake was called in to advise on the cylinder head design, and the change resulted in a very considerable uplift in power to give 105 bhp.

The extra length over the 1½ Litre was used for the six-cylinder engine and the passenger accommodation was the same size.