Camshaft settinglocking plates are used to accurately align a datum slot located in the end of the camshaft with the top face of the camshaft housing to hold the camshaft at the tdc top dead centre position locking pins are designed to pass through datum holes in the timing belt pulleys into fixed position timing holes on the engine the crankshaft tdc location pin is designed to screw into the cylinder block and provide a stop for the crankshaft to be positioned against to set the tdc po