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2.50 LITRE DIESEL ENGINE 3. New Pistons - Original pistons fitted to new engines at t h e factory are specially graded to supplied 0,025 (0.001 in) to allow for production tolerances on new engines. When fitting pistons to a standard size cylinder block the must be honed to accommodate the pistons with the correct clearances. In addition Land Rover pistons are available and (0.020 and 0.040 in) oversize for fitting to rebored cylinder blocks. limits for new standard size pistons in a standard cylinder bore measured at right angles to the gudgeon pin are in the “General specification data” section. Using a suitable micrometer measure the pistons at the bottom of skirt at right angles to the gudgeon pin. 5. With an inside micrometer or cylinder gauge measure the diameter the bore at approximately half-way down and note the reading. 6. The clearance is determined by subtracting the piston diameter from the bore diameter. 7 . If equipment is not available the clearance can assessed by placing a long, suitably sized, feeler gauge down t h e thrust side of the bore and inserting the appropriate piston, ‘upside down’, in the bore and position it with the gudgeon pin to the crankshaft axis. Push the piston down the bore and stop at the tightest point and gauge. If a steady resistance of approximately (6 Ibs) is felt, the clearance is satisfactory. Inspect piston rings Normally when an engine is being overhauled the a different purpose and the engine has only completed a small mileage. Before refitting the rings should be examined for wear and damage. In addition the rings must be checked for side in the bores. The latter two checks must be made when fitting new rings to new 8. Check gap When ring gap in worn bores, but are within the acceptable taper and ovality limits, the ring must inserted squarely into the bottom of the bore at the lowest To ensure squareness of the ring push the ring down the bore to the correct bores, the ring may be inserted into any position in the bore. 9. Using an appropriate feeler guage check the gaps of all the rings, in turn, including the oil control If any gap is less than that specified, remove ring, and file the ends whilst holding the ring in a filing jig o r vice. Should any gap be excessively wide and not likely to close-up to within the specified limits when hot, an ring be fitted. |