Jeep Engines - Oljeep

4.2L IN-LINE 6 (PISTON AND CONNECTING ROD ASSEMBLY) 295InstallationLubricate the bearing surface of each insert with cleanengine oil. Install the bearing inserts, cap and retainingnuts. Tighten to the specified torque.Caution: Care must be exercised when rotating thecrankshaft with bearing caps removed. Be sure the connectingrod bolts DO NOT accidentally come in contact with the rodjournals and scratch the finish. Bearing failure would result.Install the oil pan using new gaskets and seal. Tighten thedrain plug securely.Use new engine oil to fill the crankcase to the specified level.PISTONSAluminum alloy “Autothermic” pistons, steel reinforcedfor strength and controlled expansion, are used. Eachpiston has three piston rings, two compression and one oilcontrol ring above the piston pin.The piston pin boss is “offset” from the piston centerline toplace it nearer the thrust side of the piston.To ensure correct installation of the piston in the bore, anotch is cast into the top perimeter of the piston head. Thenotch must face forward.Piston FittingPistons are fit to their respective bores by measuring theinside diameter of the cylinder bore and the diameter of thepiston.1. Micrometer Methoda. Measure the inside diameter of the cylinder boreat a point 58.725 mm (2-5/16”) below the top ofthe bore.b. Measure outside diameter of the piston. Becausepistons are cam ground, measure at right angle topiston pin at centerline of pin (Figure 5-3).The difference between cylinder bore diameter andpiston diameter is piston-to-bore clearance.I1 - 1GROOVE HEIGHTA 2.01 93-2.0447 mrn (0.0795-0.0805 in)B 4.7752-4.8133 mm (0.1880-0.1895 in)GROOVE DIAMETERD-E 84.4296-84.5566 mm (3.324-3.329 in)F 84.5566-84.8106 mm (3.329-3.339 in)2. Feeler Gauge MethodFigure 5 - 3(Not recommended for racing.)a. Remove the rings from the piston.AMEASURE PISTONAT THIS AREAFOR FITTINGJ9009-73b. Insert a long 0.025 mm (0.001”) feeler gauge intothe cylinder bore.c. Insert the piston, top first, into cylinder borealongside the feeler gauge. With entire pistoninserted into cylinder bore, the piston should notbind against feeler gauge.d. Repeat steps with a long 0.05 I mm (0.002”) feelergauge. The piston should bind.e. If the piston binds on 0.025 mm (0.001”) feelergauge, the piston is too large or cylinder bore is toosmall. If the piston does not bind on 0.051 mm(0.0021t) feeler gauge, the piston is too small forcylinder bore. Pistons up to 0.102 mm (0.004”)undersize may be enlarged by knurling or shotpeening.Replace pistons that are 0.102 mm (0.004”)or more undersize.PISTON RINGSCarbon must be cleaned from all ring grooves. The oil drainopenings in the oil ring grooves and pin boss must becleared. Care must be exercised not to remove metal fromeither the grooves (since this will change their depth) orfrom the lands (since this will change the ring grooveclearance and destroy ring-to-land seating).Side clearance between land and compression rings shouldbe as listed in 4.2L Engine Spec$cution.s, ‘EngineAssembly’ section.. ..T -1 n