rover25 impression 1.4?

Hi. Ihave just bought a Rover 25 2002plate. There is a knocking noise from the drivers side of the engine when I start it from cold. But after a few mintues it goes away.
The clinder head gasket, tappets and timing belt have all been replaced.
The tip of the exhaust pipe is always dry, which is unusual as most have a black soot on the edge.
Please can you help?