Weslake were to make several variations of engine from 1975 onwards, including engines with OHV; SOHC and DOHC all with 4 Valves, but also an OHV with only 2 valves.
They made engines (for Speedway) with 250, 350 and 500cc motors fitted, the pictures here being of the DOHC 4 valve speedway. This engine housed a standard ignition system which was operated by contact breakers
And to add a splash of colour ........
Steve Magro from Australia kindly sent me this photo* of former Australian International and Exeter rider, John Titman's DOHC Weslake....
John described it as heavy and requiring frequent and difficult maintenance.