Following the post-war speedway boom years, it was not just in England that motorcycle manufacturers were quick to see the potential the new sport could bring. Franco Oliani sent in this interesting account of the Gilera, together with some of its historical background.
Till the beginning of the 30's, 500cc single-cylinder roadsters produced by the Gilera firm had mostly side valves. A few OHV models were built between 1924 and 1930, but they were competition machines and never put on the market. In 1933 the research into OHV engines was resumed by engineer Mario Mellone. First he designed a 3 valve bike (two inlet valves and one exhaust valve) with one carburettor and two exhaust pipes, which was followed by a 2 valve model a year later.
After this experimental period, the OHV engine known as the 'VT' came into full mass production in 1935. The first model was called simply 'quattro bulloni' (four bolts) referring to the number of bolts fixing the cylinder base to the sump. Afterwards, this number was doubled giving rise to the better known appellative 'otto bulloni' (eight bolts).
The engine had maintained the usual dimensions (bore: 84mm and stroke: 90mm). The timing system had only two valves inclined 70 degrees (35+35) and one exhaust pipe with a bulky expansion silencer. The oil tank was in the engine sump, while the 4-speed gearbox was put in a separate box with self contained lubrication. The bikes adapted to racing were called 'VTEGS' which stands for Valvole in Testa, telaio Elastico, Gran Sport. They differed from the 'VT' for the compression ratio (7:1 instead of 5,5:1), carburettor (28.5mm instead of 27mm) and power (24hp at 4,800 revs instead of 20hp at 4,500 revs). In the 'Formula Sport' contests these machines entered into competition with the Moto Guzzi 'C' (later 'Condor'), the SOHC Benelli and the DOHC Taurus too.
After the war the 'otto bulloni' machines were employed in minor races and most of them mounted a different fuel tank. In those years Italian speedway riders adapted to dirt track racing roadsters built by Benelli, Ceccato, Rumi, Mondial, CM, Moto Guzzi and, of course, Gilera; the 'Otto Bulloni' was among them. Dario Basso from Arzignano is one of the legend of Italian speedway who rode a Gilera. The picture above shows him after a victorious race astride the machine with number 13, which is, I'm almost sure, a Gilera 'Otto Bulloni'. The other rider might be Valerio Facchin on what looks like a 350cc CM machine.
