I have a 52 plate s40 bi fuel,200k miles, was running like a dream, ticked over at 850rpm and sounded sweet, at 200k i have had the cam belt changed it now ticks over between 850 and 1000 rpm, there sounds like a whirring noise when driven and there is a clicking type noise somewhere at the top of the engine, it is driving ok but it is not the same car, by the way i didn't changethe belt myself....lol.....as well as the belt there was an alternator belt fitted and the pulleys as recommended, anyone got any ideas please