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Jaguar and the Gas Meter

SS Cars Ltd was innovative in many ways but probably the biggest single factor that propelled them to real success was the first Jaguar engine and foremost in that development must be Harry Weslake. Thereafter Weslake's services were engaged in the design of every Jaguar engine right up to and including the V12. 

 See also: A comparison of the SS engine to the XK

Weslake, the son of Henry John Weslake a director of Willey & Co. had been a keen motorcyclist since his teens and took part in competitive events with some success. By age 17 he had acquired his first patent for an improved carburetter design, the Wex and after starting up his own company to manufacture these carburetters he became involved in sponsoring one of his employees, Gordon Cobbold, in racing a Sunbeam motorcycle at Brooklands. The Sunbeam company also sponsored Cobbold allowing him to break various class records at the famous track. For the air flow development of his Wex carburetters Weslake was fortunate to have gained experience from his apprenticeship activities with Willey and Co. who manufactured gas meters. Air flow rates through his carburetters were literally measured by a gas meter.

With Cobbolds track successes at Brooklands one thing led to another and Weslake's expertise was called upon to explain the manufacturing differences between good and bad performing Sunbeam engines taken from their regular production. Testing the gas flow through various Sunbeam cylinder heads with a gas meter from his father's company he could see that power output related directly to flow rate through the ports. Thus by progressive modification and measurement he was able to make considerable improvements in flow rates and power output.

With effective gas flow test methods and a good sense of what worked and what didn't, Weslake brought power improvements to many engine designs in the 1920s and 30s and in 1934 he joined SS Cars Ltd as a consultant to the design of the first Jaguar engine. This engine started life as the 20 hp 6 cylinder side valve unit produced by the Standard Motor Company that delivered a maximum power of 65 bhp at 3800 rpm.

See also: Meet the Cousins

William Lyons had no engine design or manufacturing facilities in 1934 and relied entirely on Standards for his engines. Knowing that for his next generation of cars he would need at least 90 bhp to achieve the levels of performance that he was seeking he was very fortunate in that Harry Weslake had recently fallen out with Cecil Kimber and was only too happy to aid MG's competitor.

See also: Competition from MG SA and WA

At their first meeting, referring to Lyons' side valve cars, Weslake is reputed to have said "Your car reminds me of an overdressed lady with no brains - there's nothing under the bonnet!" The conversation then proceeded with Lyons explaining that they were looking for 90 hp for their next model and a contract was signed on the basis that Weslake should to produce a design that exceeded 95 bhp. In fact Weslake's overhead valve design gave in excess of 103 bhp when tested much to the pleasure of all concerned with the possible exception of Cecil Kimber and the team developing his MG SA.