Haynes manual says 47.5mm (page 3A.10 - engine manual), but im not absolutely sure if this is correct, as 'Crypton' data says 46.5mm. The thing is, I used to have an Orion 1.8D, and after replacing the cambelt (using the Haynes measurment - 47.5mm), felt that it was very slightly under powered, so started to investigate and found these differant measurments. Never got round to trying out 46.5mm, as the car got stolen shortly afterwards.
Pushrodman, April 2013