Nov 17

Nov 17 Guide: Jaguar XK150

Jaguar - Jaguar XK - 1950s British Cars - 1950s Supercars - 1960s British Cars - 1960s Supercars

Background

When Jaguar unveiled the XK120 at the London Motor Show in October 1948, the stunning two-seat Roadster caused a sensation. The attraction was obvious: Jaguar had created arguably the best-looking sports car on the market and, thanks to a powerful new straight six engine under the hood, the aerodynamically-styled machine would likely be the fastest production car in the world.

Although originally conceived purely to help publicise Jaguar’s state-of-the-art dual overhead camshaft engine, the XK120’s reception convinced the firm to put it into production. Eight months later, the first cars began to roll out of Jaguar’s Coventry factory.

Over the next five years, 12,000 XK120s were delivered in a combination of Open Two Seat Roadster (OTS), Fixed Head Coupe (FHC) and Drop Head Coupe (DHC) body styles. The model also scored a number of significant competition victories and set a variety of international speed records.

In late 1954, the XK120 was replaced by the XK140 which ushered in a number of cosmetic and mechanical updates.

By 1957, although the XK platform was nearing the end of its production life, there was still time for one final iteration: the XK150.

The ‘150’ was the most refined XK yet. The majority of updates focused on the exterior and interior. However, the addition of disc brakes was also a major advancement.

The XK150 was launched in May 1957 and initially came in a choice of FHC and DHC body styles. An OTS Roadster joined the line up ten months later in March 1958. From October 1959, Jaguar also offered a larger 3.8-litre engine which, like the 3.4, came in several alternative states of tune.

In addition to the XK150, Jaguar’s product line included the Mark 1 Saloon which they had produced since 1955. Like the D-type sports racing car, the Mk1 was built around an advanced steel monocoque bodyshell. The XK150’s eventual replacement, the fabled E-type, would follow suit in this regard.

Chassis

Unlike the Mk1 and subsequent E-type, the XK150 stuck with a traditional separate box-type steel chassis. As per the ‘120’ and ‘140’, this was a shortened, simplified and lightened version of the one used by the Mark V.

Independent front suspension was via wishbones, torsion bars, telescopic dampers and an anti-roll bar. The live Salisbury rear axle was located with semi-elliptic leaf springs. It used the same telescopic rear shock absorbers introduced on the XK140, which replaced the lever arms of the XK120.

Instead of the XK140’s Lockheed drum brakes, servo-assisted 12-inch Dunlop discs were now fitted at either end.

Most cars came equipped with 16 x 5.5-inch centre-lock wire wheels although some were specified with steel wheels that could be fitted in conjunction with rear wheel spats.

A 14 gallon (63.6-litre) fuel tank was installed over the rear axle.

Engine / Gearbox

Under the hood was the same straight six engine fitted to the XK140.

This William Heynes-designed power unit featured a cast-iron block and aluminium alloy head with dual overhead camshafts, hemispherical combustion chambers and inclined valves. Wet-sump lubrication was employed along with single plug ignition and a Lucas coil.

Displacement was 3441cc thanks to a bore and stroke of 83mm and 106mm respectively.

Two SU H6 sidedraught carburettors were fitted and, for most markets, a compression ratio of 8.0:1 was adopted. In this configuration, peak output was 190bhp at 5500rpm and 210lb-ft at 2500rpm.

Transmission was via a Moss four-speed manual gearbox or an optional three-speed automatic sourced from Borg-Warner.

Special Equipment Option

In addition to the standard 190bhp engine, Jaguar offered the Special Equipment upgrade that included their B-type cylinder head which had been developed from the C-type head fitted to previous iterations of the SE.

The new B-type head most notably featured enlarged exhaust valves. The rest of the upgrade pack included high lift camshafts, a 9.0:1 compression ratio, heavier torsion bars and twin exhausts. Wire wheels and fog lights were standard.

The XK150 SE developed 210bhp at 5500rpm which was 250rpm lower than the XK140 iteration.

Even more importantly, the torque rating was 216lb-ft at 3000rpm compared to 213lb-ft at 4000rpm for the outgoing XK140 SE.

Bodywork

As before, body panels were manufactured predominantly from steel. Exceptions were the hood and trunk lid which were formed from aluminium.

Although the XK150 closely resembled its predecessors, Jaguar brought in a number of subtle but significant revisions to update the XK line for its last few years of production.

The easiest change to spot was a new single-piece wraparound windscreen instead of the old two-piece split-screen.

To increase cockpit space and make access easier, FHC and DHC variants came with a windscreen that was moved four-inches further forward.

Up front, the hood was widened and given a noticeably broader 16-bar instead of seven-bar grille.

To further modernise the XK’s appearance, the tops of the front fenders were flattened thus giving a more integrated look. Similarly, down each flank, the previously curvaceous line the flowed from the front to the rear fenders was straightened lending a more contemporary, slab-sided appearance. This in turn enabled the doors to be more neatly integrated.

The doors themselves were now thinner to further increase cockpit space.

FHC variants came with a larger curved rear window.

Interior

Inside, the XK150 featured a new dash layout. The large read outs for road and engine speed (previously located at either end of the dash) were now positioned centrally. In between them was a small ammeter and the toggle switch for the lights.

A fuel gauge and combined oil / water temperature read out were mounted on the left and right-hand side of the dash respectively.

As before, the clock was integrated within the rev counter.

A variety of switches were scattered along the base of the dash. One new feature was a red warning light which notified the driver if the parking lights had been left on.

Although the walnut veneered dash and door caps used previously were still available as an option, as standard they were now upholstered in leather. An alloy dash fascia was also available.

To reflect the extra space inside, subtly revised seats were installed. Once again, the FHC variant came with two small rear seats.

Leather was used to upholster practically every surface that wasn’t carpeted.

Options

In addition to the Special Equipment package, Jaguar offered a variety of optional extras.

Buyers could have the exterior of their XK150 enhanced with Lucas fog lamps, a leaping Jaguar mascot for the hood, a chromed luggage rack for the trunk, a chromed badge bar, Dunlop Road Speed tyres with whitewalls and steel wheels with chrome hub caps and rear wheel spats.

Performance upgrades included a dual exhaust system, close-ratio gearbox and Dunlop racing tyres.

Instead of the standard 8.0:1 compression ratio, a 7.0:1 or 9.0:1 ratio could be requested. A steel underbody shield gave protection against adverse road conditions.

Cockpit extras included fitted luggage (two suitcases to match the rest of the interior), a choice of Radiomobil radios, an aluminium dash, bucket seats and a white or wood finished Bluemels steering wheel.

The FHC could be specified with a Weathershields sunroof.

The DHC could be specified with a full-length tonneau cover.

Weight / Performance

The XK150 FHC weighed in at 1473kg while the DHC variant was slightly lighter at 1460kg. In comparison, the outgoing XK140s had both tipped the scales at 1420kg.

Top speed of the standard (non-SE) XK150 variants was 124mph compared to 125mph for the equivalent XK140s. The XK150’s 0-62mph time was a tenth quicker at 8.3 seconds.

OTS Roadster

Ten months after the XK150 was launched in FHC and DHC configurations, Jaguar added a sporty OTS Roadster to the line up.

Available from March 1958 (the first left-hand drive prototype had been completed in September 1957), the XK150 Roadster came with a number of features not seen on previous OTS variants.

Most notably, conventional wind-up windows were adopted whereas earlier incarnations had used detachable side screens.

Another departure from previous Roadsters was the addition of external push-button door handles (access to the cockpit of XK120 and XK140 Roadsters had been via an interior pull-cord).

As usual, this latest Roadster retained the simple folding roof of its predecessors.

Compared to FHC and DHC variants of the XK150, the OTS had its windscreen mounted four-inches further back which meant the quarter lights had to be deleted.

At 1447kg, the OTS was the lightest XK150 available.

3.4 S Engine Option

At the same time as the OTS Roadster was launched (March 1958), Jaguar introduced a more potent version of their 3.4-litre engine.

The S engine (which was not available with an automatic gearbox) came with triple SU HD8 carburettors instead of twin HD6 units. It also featured a new straight port cylinder head to improve air flow.

Cars ordered to S specification came with all the Special Equipment trim as standard.

The result was a peak output of 250bhp at 5500rpm and 240lb-ft at 4500rpm.

In comparison, the standard 3.4 produced 210bhp at 5500rpm and 210lb-ft at 2500rpm. The SE pumped out 210bhp at 5500rpm and 216lb-ft at 3000rpm.

Unsurprisingly, the 3.4 S was the fastest XK150 yet; all three body styles could hit around 135mph while the 0-62mph time dropped to a little over seven seconds.

Production Changes

Production changes made during the course of 1958 included the discontinuation of the aluminium dash option and the switch from 54 to 60-spoked wire wheels.

3.8 & 3.8 S Engine Option

At the London Motor Show in October 1959, Jaguar launched a brace of new 3.8-litre engine options for the 1960 model year.

The 3.8 motor had already seen service in the Mark IX Saloon which had been launched a year earlier. It was bored from 83mm to 87mm while stroke remained unchanged at 106mm. This gave a displacement of 3781cc which was a 339cc gain over the 3.4-litre unit.

Both iterations of the 3.8-litre engine ran an 8.0:1 compression ratio.

The 3.8 SE came with two SU HD6 carburettors. It produced 220bhp at 5500rpm and 240lb-ft at 3000rpm. Top speed was 130mph and 0-62mph took 7.4 seconds.

The top-of-the-range 3.8 S came with triple SU HD8 carbs. Peak output was 265bhp at 5500rpm and 260lb-ft at 4000rpm. Top speed was 137mph and 0-62mph took 7.1 seconds.