The Tempest 10 cc racing engine was an Australian-made copy of the 1946 McCoy 60 black-case model from America. It was a joint venture between Hearns Hobbies of Flinders Street in Melbourne, Victoria and a company called Lynella Engineering Works, also of Melbourne. Lynella was responsible for the engine's manufacture, while Hearns Hobbies assumed the marketing role.  

The Tempest was introduced in late 1947 in an effort to provide Australian competition modellers with a lower-cost alternative to the American racing engines whch were extremely expensive if they could be obtained at all.  It suceeded in the short term, apparently selling reasonably well at the outset and acquiring a good reputation for high quality and dependability.  However, its performance didn't match that of its American competition, as a result of which it never made much of a mark in Australian contests of the day. Its best showing against strong opposition was a third place at the 1948 Australian Nationals in Class D speed. Its one Nationals win came in 1950 more or less by default at a meeting which was not attended by any of the top Australian competitors.

The Tempest was produced in two distinct variants. The first model had a black case and sported the letters H T H  on the bypass.  The second model had a plain case (some of which were steel grit shot-blasted) and bore the TEMPEST name on the bypass. Both variants had a green-anodized cylinder head. A glow-plug version of the second model was also offered. This differed only in lacking a timer and an access window in the main bearing housing for the cam follower.

Reportedly some 400 examples of all variants ended up being manufactured and sold, some 250 of them being the glow-plug model. A full review of the Tempest racing engine and its Australian-made competitors may be found elsewhere on this website.