The open two-seater was fitted for the first time with wind-up windows in taller high-silled doors, but retained the very simple folding roof of its predecessors.

Most visibly, a one-piece windscreen replaced the split screen, and the wing line carried higher and more streamlined at the doors.

The widened bonnet opened down to the wings, and on the coupés the windscreen frame was moved forward 4 inches (102 mm) to make passenger access easier.

The 3.4 litre DOHC straight-6 XK engine was similar to the XK140's, but a new "B" type cylinder head raised power to 180 SAE bhp at 5750 rpm.

After a twelve-month delay caused by the February 1957 factory fire, this deficit was corrected in the spring of 1958 with the March release of special equipment models fitted with disc brakes and more powerful SE engine.

Twin 1.75-inch (44 mm) SU HD6 carburettors and a modified B type cylinder head with larger exhaust valves improved performance to 210 SAE bhp at 5500 rpm.

While most export cars were SE models, a third option for the open two-seater featured an "S" engine with three 2-inch (51 mm) SU HD8 carburettors and a straight-port cylinder head boosting power to a claimed 250 SAE bhp.