The 3-Litre was fitted with a higher displacement 2.9 L 140 bhp version of the twin overhead camshaft Lagonda Straight-6 engine designed by Walter Owen Bentley.

[1] In early 1955, the Mark II version introduced a floor-mounted gear lever.

At the front there were coil springs and at the rear torsion bars and a swing axle.

The Lockheed drum brakes, 12 in (305 mm) at the front and 11 in (279 mm) at the rear were servo assisted and steering was by a rack and pinion system with fore and aft adjustment on the steering column.

The interior was luxurious with polished walnut for the dashboard and door trims and leather seats, individual in the front and a bench at the rear with a central fold down arm rest.