The Mark 1 Saloon
In 1955 Jaguar introduced the Mark 1 compact saloon to fill the niche between its two seater sports cars and the larger six seater Mark VII. The Mark 1 was a 2.4 litre car designed from the start with an eye to economy, but such was its potential that it was soon given the larger 3.4 litre engine to make it one of the fastest saloon cars in the world.
What really set the Mark 1 apart from all other Jaguar saloons, was its unitary method of construction a new venture for Jaguar. This type of body in which the basic shell doubled as the chassis had two significant advantages: that it saved weight and was inherently more rigid. Stress engineering for cars was in its infancy in the 1950s, so the Jaguar Mark 1s body shell was, if anything, too strong and heavy, but it was still much more efficient than the older system of separate chassis.
With such as stiff basis to the car, relatively soft suspension could be used, which paid dividends in ride and roadholding. The front suspension was similar to that of the Mark VII saloon, except that it used coil springs rather than torsion bars because Jaguar were not confident that the bodyshell would be strong enough to take the stress of the torsion bar rear anchorage points. The rear suspension used normal half elliptic springs turned upside down, with one end attached to the live rear axle and the front half clamped to the bodyshell so that they acted, in effect, as quarter elliptic springs. An adjustable Panhard rod stopped the axle moving sideways and trailing arms prevented it from twisting under power.
In March 1957, the 3.4 litre engine was introduced to the Mark 1. The power unit was exactly the same as the one fitted to the Mark VIII saloon, complete with B type cylinder head, SU carburettors and twin exhausts, linked to either a manual or automatic gearbox. The rear axle was strengthened by incorporating Mark VIII components and a larger radiator was fitted. This meant that the front of the car had to be restyled to accommodate a wider radiator grille. The new frontal appearance was standardized on the 2.4 litre Mark 1 six months later, together with cutaway rear spats, which were fitted to the 3.4 litre Mark 1 to help brake cooling.