Four new copper washers need to be acquired for fitting to the pump mounting bolts during the refitting process as early models may not have any washers upon dismantling. To start, perform the required operations and remove the four bolts that hold the oil pump on the cylinder block. Carefully remove the pump assembly by prying behind the upper and the lower parting lug with a screwdriver to remove the pump and recover the gasket. Clean the mating face of the pump and cylinder block very well and make sure to remove all residues of the old gasket. Next take out the two screws holding the two halves of the pump together and take off the gear cover, ready to catch the pressure relief valve spring. Extract the relief valve spring, plunger and pump gears, carefully lever out the crankshaft oil seal, getting a new seal for refitting. Clean all the components thoroughly and check the gears, the body, and the gear cover for any signs of wear or damage. Measure the free height of the pressure relief valve spring and match it with the specified dimension, renewing it if weak or distorted as well as checking the plunger for any scoring or damage. Refit the gears to the pump body with the markings on the large gear uppermost, checking the clearance between the large gear and pump body using feeler blades and if the clearance is outside the specified limit then pump should be renewed. If satisfactory, lubricate the gears, lubricate and fit the relief valve plunger and spring. Fit a new O-ring seal to the pump body, and then put on the cover and lock it with the two screws. Using a new gasket, fit the pump to the block, placing new copper washers on the pump retaining bolts, draw the pump into place using the crankshaft pulley nut and spacers, making sure not to damage the seal in the oil pump, and not to rotate the crankshaft during fitting. After the pump is set, tighten the retaining bolts diagonally to specified torque. Lubricate the cover, crankshaft and new oil seal and install the seal with the lips inwards using a piece of tube or the old seal inverted to tap it into place until flush. Finally, refit the crankshaft sprocket and pulley in reverse of the removal procedure, and refit the timing belt.