Like HowStuffWorks on Facebook!

Jaguar SS 100


Jaguar SS 100 Design

The Jaguar SS 100 entered its final development during the latter part of 1935. Compared to its predecessor, the Jaguar SS 90, engine improvements were the big news.

Jaguar SS 100 rear
Rakish, fast, and affordable, the Jaguar SS 100
was a smashing commercial success.

Thanks to work done by consultant Harry Weslake for the new SS Jaguar sedan, introduced at the same time, the Jaguar SS 100 arrived with an overhead-valve cylinder head. The twin carburetors, now SUs instead of the older RAGS, were still on the left side, but the exhaust manifold had been moved to the right to make an efficient cross-flow design.

Even for the day, this was not startling technology, for the head was cast in iron and operated the valves through pushrods. But Weslake's genius had somehow conjured up startling results. Lyons had asked him to raise the output of the side-valve 2.7-liter from 75 horsepower to about 90. With his overhead valve head, Weslake raised it beyond 100; on the dynamometer, the test engine showed 105 horsepower at 4,500 rpm. The production unit was almost as good: 104 at 4,600.

Though little changed from the SS 90 in basic dimensions and basic chassis design, the Jaguar SS 100 arrived with a somewhat different steering mechanism and much bigger brakes operated by rod, rather than cable.

Suspension was revised, too, with some parts adopted from the new sedan. Curiously, front shock absorbers were now a combination of Hartford friction and Luvax hydraulic shocks, but only the latter were used at the rear. Tires were the same size, but the wire wheels were now supplied by Dunlop instead of Rudge-Whitworth, and had different hubs.

Visually, the biggest alteration from the SS 90 to the Jaguar SS 100 occurred at the rear, where the gas tank's back wall now slanted forward, and thus so did the spare wheel. However, someone standing toward the nose of the car could easily notice a difference in the front wings, where the leading edges had a more florid droop. There were also some bumper, grille and, of course, badging differences.

The SS Jaguar 100 went on sale in March 1936, and was an immediate hit. It was a faster car, also a better car, and it listed for a still-remarkably low 395 British pounds. The sporting public responded. Over the next two years, well over 100 "100"s were sold, and many did well in various sorts of speed and endurance events, including international rallies.

According to a contemporary road test in The Motor, Britain's second-oldest automotive journal (after The Autocar), a 2.7-liter SS 100 could do 0-60 mph in 12.8 seconds. At the time, that was quick enough to shut down most locally made opposition. Similarly, the quarter-mile time of 18.6 seconds was considered "outstanding."

As for top speed, the magazine timed its car at 96 mph. Another publication got a little less, but even with the full-sized windshield in its upright position the car could hit 90. In normal motoring, 75 was regarded as an easy cruising speed.

The Jaguar SS 100 got more speed for 1938. In conjunction with developing its new "all-steel" sedan, Jaguar bored and stroked the sturdy old Standard six-cylinder engine to 82x110 mm.

This brought its capacity up to 3,485.5 cc (212.7 cubic inches), a resounding 31 percent more and nearly 75 percent over the old 2.1-liter with the same basic block. To handle the extra stress, the chrome-iron crankcase was made stiffer; to handle the extra gas flow, the overhead valve head was revised to have six individual exhaust ports.

Steel connecting rods were adopted, finally, to cure the old hot-oil pressure problem. On a compression ratio of 7.2:1, horsepower was said to be 125 at 4,500. Inevitably, price went up too, but only to a still-very-competitive 445 British pounds.

It was well worth it. Genuinely much quicker than the 2.7-liter model, the "3-1/2-Litre" SS 100 amazed the enthusiast press of the day. Zero-to-60 mph acceleration times dropped below 11 seconds (to 10.4, said The Motor) and, at least with the main windshield folded down flat, the "100" proved to be a 100-mph car by one or two mph.

These figures may not look very impressive today, but to better them in Great Britain during the late 1930s, one had to buy a much more expensive car -- or maybe a 998-cc Vincent-HRD motorcycle.

For more on Jaguar and other great cars, see:

  • Jaguar Cars: Check out more information on the great sporting cats.
  • How Sports Cars Work: Get the lowdown on hundreds of fantastic sports cars from the 1940s to today.
  • Classic Cars: Learn about the world's most coveted automobiles in these illustrated profiles.
  • Ferrari: Learn about every significant Ferrari road car and racing car.
  • New Jaguars: Reviews, ratings, prices, and specifications on the current Jaguar lineup from the auto editors of Consumer Guide.
  • Used Jaguars: Reviews, recalls, trouble spots, and more on pre-owned Jaguars starting with the 1990 model year. From the auto editors of Consumer Guide.

More to Explore