Engine                                                                                                                                Disassembly and Assembly The serviceman must be very careful to use Plastigage correctly.  The following points must be remembered: a. Make sure that the backs of the bearings and the bores are clean and dry. b. Make sure that the bearing locking tabs are properly seated in their slots. c. The crankshaft must be free of oil where the Plastigage touches it. d. If the main bearing clearances are checked with the engine upright or on its side, the crankshaft must be supported.  Use a lack under an adjacent crankshaft counterweight and hold the crankshaft against the crown of the bearing.  If the crankshaft is not supported, the weight of the crankshaft will cause incorrect readings. e. Put a piece of Plastigage on the crown of the bearing half that is in the cap.  Do not allow the Plastigage to extend over the edge of the bearing. f. Install the bearing cap using the correct torque-turn specifications.  Do not use an impact wrench.  Be careful not to dislodge the bearing when the cap is installed. g. Do not turn the crankshaft with the Plastigage installed. h. Carefully remove the cap but do not remove the Plastigage.  Measure the width of the Plastigage while it is in the bearing cap or on the crankshaft journal.  Do this by using the correct scale on the package.  Record the measurements. j. Remove the Plastigage before reinstalling the cap. When using Plastigage, the readings can sometimes be unclear.  For example, all parts of the Plastigage are not the same width Measure the major widths to make sure that they are within the specification range.  Also, experience has shown that when checking clearances tighter than 0.10 mm (.004") the readings may be low by 0.013 to 0.025 mm (.0005 to .0010").  Out-of-round journals can give faulty readings.  Also, journal taper may be indicated when one end of the Plastigage is wider than the other. For complete details concerning measuring bearing clearances, see Engine Bearings And Crankshafts, Form No.  SEBD0531. 5. Check the main bearing clearance with Plastigage (B) as follows: a. Put a piece of Plastigage (B) on the crankshaft journals as shown NOTICE Make sure the part number on the main bearing cap is toward the front of the engine and the number on the main bearing cap is the same as the number on the cylinder block on the left side of each main bearing cap. b. Put main bearing caps (1) in position in the engine. Put clean engine oil on the bolt threads and the face of the washers, and install the bolts.  Tighten the bolts to a torque of 40 + 4 N•m (30 + 3 Ib.ft.). c. Put a mark on each bolt and main bearing cap; then tighten the bolts 90 more. d. Remove the main bearing caps, and measure the Plastigage to find the bearing clearance.  The main bearing clearance for new bearings must be 0.076 to 0 165 mm (.0030 to .0065 in.).  Maximum permissible clearance with used bearings is 0.25 mm (.010 in.). 95