Jeep Engines - Oljeep

4.2L IN-LINE 6 (CRANKSHAFT) 287Inspection1. Wipe inserts clean and inspect for abnormal wearpatterns and for metal or other foreign materialimbedded in the lining. Normal main bearing insertwear patterns are shown in Figure 2-14.2.3.4.5.If any of the crankshaft journals are scored, remove theengine for crankshaft repair.FittingInspect the back of the inserts for fractures, scrapings,or irregular wear patterns.Inspect the upper insert locking tabs for damage.Replace all damaged or worn bearing inserts.The main bearing caps, numbered (front to rear) from 1through 7 have an arrow to indicate the forward position.The upper main bearing inserts are grooved to provide oilchannels while the lower inserts are smooth.Each bearing insert pair is selectively fit to its respectivejournal to obtain the specified operating clearance. Inproduction, the select fit is obtained by using various-sizedcolor-coded bearing insert pairs. The bearing color codeappears on the edge of the insert. The size is not stamped onbearing inserts used for engine production.The main bearing journal size (diameter) is identified inproduction by a color-coded paint mark on the adjacentcheck toward the flanged (rear) end of the crankshaft,except for the rear main journal, which has the mark on thecrankshaft near the flange.When required, upper and lower bearing inserts of differentsizes may be used as a pair. A standard size insert issometimes used in combination with a 0.025 mm (0.001")undersize insert to reduce the clearance by 0.013 mm(0.0005"). Never use a pair of bearing inserts with greaterthan a 0.025 mm (0.001") difference in size.Note: When replacing inserts, the odd size inserts must beeither all on the top (in cylinder block) or all on the bottom(in main bearing cap).Main Bearing-to-Journal Clearance - CrankshaftInstalledWhen using Plastigauge, check only one bearing clearanceat a time.1. Install the grooved main bearings into the cylinder blockand the non-grooved bearings into the bearing caps.2.3.4.Install the crankshaft into the upper bearings dry.Place a strip of Plastigauge (P4286819) across the fullwidth of the crankshaft journal to be checked.Install the bearing cap and tighten the bolts to 108 N*m(80 ft-lbs) torque.5.6.7.8.9.Note: DO NOT rotate the crankshaft. This will causethe Plastigauge to shift, resulting in an inaccuratereading. Plastigauge must not be permitted to crumble.If it is brittle, obtain fresh stock.Remove the bearing cap. Determine the amount ofclearance by measuring the width of the compressedPlastigauge with the scale on the Plastigauge envelope.The correct clearance is 0.0254 to 0.0635 mm (.0010 to.0025") for all main bearing journals, with 0.051 mm(0.002") preferred.Plastigauge should indicate the same clearance acrossthe entire width of the insert. If clearance varies, it mayindicate a tapered journal or foreign material trappedbehind the insert.If the specified clearance is indicated and there are noabnormal wear patterns, replacement of the bearinginserts is not necessary. Remove the Plastigauge fromthe crankshaft journal and bearing insert. Proceed toCrankshaft Main Bearing Installation.If the clearance exceeds specification, install a pair of0.025 mm (0.001") undersize bearing inserts andmeasure the clearance as described in the previous steps.The clearance indicated with the 0.025 mm (0.001")undersize insert pair installed will determine if thisinsert size or some other combination will provide thespecified clearance.Example: If the clearance was 0.0762 mm (0.003")originally, a pair of 0.0254 mm (0.001") undersizeinserts would reduce the clearance by 0.0254 mm(0.001"). The clearance would then be 0.0508 mm(0.0021') and within the specification. A 0.0508 mm(0.002t1) undersize bearing insert and a 0.0254 mm(0.001") undersize insert would reduce the originalclearance an additional 0.0127 mm (0.0005") and theclearance would then be 0.0381 mm (0.0015'l).Caution: Never use a pair of inserts that differ morethan one bearing size as a pair. For example, DO NOTuse a standard size upper insert and a 0.051 mm(0.002") undersize lower insert.If the clearance exceeds the specifications using a pairof 0.051 mm (0.0021t) undersize bearing inserts,measure the crankshaft journal diameter with amicrometer. If the journal diameter is correct, thecrankshaft bore in the cylinder block may bemisaligned, which requires cylinder block replacementor machining to true bore.If the diameter for journals 1 through 6 is less than63.4517 mm (2.4981") or journal 7 is less than 63.4365mm (2.4975"), replace the crankshaft or grind it downto accept the appropriate undersize bearing inserts.Once the proper clearances have been obtained, remove thecrankshaft and proceed to Installation.