5. Fit Valve guide oil seals 4. Valve Seat 1. Check valve seat height with respect to cylinder head mating surface. Replace valve seat inserts if they are worn out beyond specified limit. 2. Cut exhaust and inlet valve seats with a general 45o cutter. 3. If necessary lap the valve seats to a smooth and even finish by using suitable hand pump grinder or a lapping paste and valve itself. 4. Smear valve seat with carbon blue. Install valve in guide and turn it slowly under axial pressure. 5. Contact line on valve seat must be around entire circumference at equal width. 6. Distance between narrow diameters of valve face to contact line should be minimum 0.5 mm. 7. Check for leakages through valve seat by pouring fuel on valve head. Fuel must not seep past valve seat. 5. Valve Seat Insert 1. For removing valve seat inserts from cylinder head use suitable boring machine. Bore old insert thin (About 0.5 mm thickness) and then pry it out. 2. Alternatively use a suitable turning tool to cut an annular groove into valve seat insert and then pull it out with a suitable puller. In order to avoid damaging machined cylinder head mating surface with crank case, place any soft protective sheet metal under supports of puller. 3. Measure valve seat insert bore diameter in cylinder head. 4. If boring and prying is done carefully without damaging valve seat insert bore in cylinder head, fitment of an oversize valve seat insert will not be necessary. 5. Re-machined valve seat insert bore in cylinder head must be exactly at right angle to cylinder head mating surface with crank case. 6. All specified dimensions should be strictly maintained to ensure proper interference of valve seat insert in its bore. 7. Clean valve seat insert and its bore in cylinder head thoroughly. 6. Just Before Installation 1. Place valve seat insert in mixture of Methanol and dry ice for about 20-30 minutes to bring temperature down to -150°C. 2. He at cylinder head to approximately 80°C in hot water bath. 3. Install valve seat insert in cylinder head bore quickly by light hammering. 4. Machine valve seat in cylinder head. 7. Cam Shaft 1. Check cam shaft run out at 2nd journal by supporting it on V-block at 1st and 3rd journal. 2. Check cam shaft journal dimensions. Record the readings. 3. Carry out visual inspection of cam shaft for. Overheating of journals, this is indicated by • bluish/ brown colour. Deep scoring marks on journals and cam lobes • Cracks, which should be checked on a • magnetic crack detector. 4. Check hardness of cam shaft journals and cam lobes, it should be 45 HRC. 8. Hydraulic Lash Adjuster Hydraulic Lash Adjuster supports the pivot end of the rocker arm while automatically controlling the rocker arm position to keep it in contact with the camshafts and valve. The range of the hydraulic lash adjuster accommodates engine build tolerances; hence no adjustment is required during engine assembly. It also compensates for variation that occurs during the life of the engine. For information on HLA and inspection refer Lubrication section. NOTE Valve seat must be absolutely faultless and • without any chatter marks Diesel Engine Ph-2 (CAFÉ) 156
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