Jeep Engines - Oljeep

l- ' T r l4.0L POWER TECH IN-LINE 6 (PISTONS AND RINGS) 159Inspection1. Connecting Rod BearingsInspect the connecting rod bearings for scoring andbent alignment tabs. Check bearings for normal wearpatterns, scoring, grooving, fatigue and pitting.Replace any bearing that shows abnormal wear.Inspect the connecting rod journals for signs ofscoring, nicks and burrs.2. Connecting RodsMisaligned or bent connecting rods can causeabnormal wear on pistons, piston rings, cylinder walls,connecting rod bearings and crankshaft connecting rodjournals. If wear patterns or damage to any of thesecomponents indicate the probability of a misalignedconnecting rod, inspect it for correct rod alignment.Replace misaligned, bent or twisted connecting rods.Cylinder Bore MeasurementRefer to 'Block' section of this chapter for the procedure.Fitting Pistons- Bore Gauge MethodTo correctly select the proper size piston, a cylinder boregauge capable of reading in 0.003 mm (.OOOl")INCREMENTS is required. If a bore gauge is not available,DO NOT use an inside micrometer.1. Measure the inside diameter of the cylinder bore at apoint 49.5 mm (1-15/16") below top of bore. Startperpendicular (across or at 90 degrees) to the axis of thecrankshaft at point A and then take an additional borereading 90 degrees to that at point B (Figure 2-34).2.3.4.Coated pistons, piston pins and connecting rods arepre-assembled. The coated piston and connecting rodassembly can be used to service previously builtengines; however, they MUST be replaced as completesets. Tin coated pistons should not be used asreplacements for coated pistons.The coating material is applied to the piston after thefinal piston machining process. Measuring the outsidediameter of a coated piston will not provide accurateresults. Therefore measuring the inside diameter of thecylinder bore with a dial bore gauge is MANDATORY.To correctly select the proper size piston, a cylinderbore gauge capable of reading in 0.003 mm (.0001")increments is required.Piston installation into the cylinder bore requiresslightly more pressure than that required for noncoatedpistons. The bonded coating on the piston willgive the appearance of a line-to-line fit with thecylinder bore.Piston Size ChartCylinder BoreSizePiston LetterSize98.438 to 98.448 mm A(3.8755 to 3.8759")98.448 to 98.458 mm B(3.8759 to 3.8763")98.458 to 98.468 mm C(3.8763 to 3.8767")98.468 to 98.478 mm D(3.8767 to 3.8771")98.478 to 98.488 mm E(3.8771 to 3.8775")98.488 to 98.498 mm F(3.8775 to 3.8779")Fitting Rings1. Carefully clean the carbon from all ring grooves. Oildrain openings in the oil ring grooves and pin bossmust be clear. DO NOT remove metal from thegrooves or lands. Doing so will change ring-to-grooveclearance and will damage the ring-to-land seating.2.3.Measure the ring side clearance with a feeler gauge fitsnugly between the ring land and ring (Figure 4- 13 andFigure 4-14). Rotate the ring in the groove. It mustmove freely around the circumference of the groove.RinP Side Clearance MeasurementTop Compression RingSecond Compression RingOil Control RingPlace ring in the cylinder bore and push down with aninverted piston to position near lower end of the ringtravel. Measure ring gap with a feeler gauge fit snuglybetween ring ends (Figure 2-39).Ring GaD MeasurementTop Compression RingSecond Compression RingOil Control Ring0.042 to 0.084 mm(0.0017 to 0.0033")0.042 to 0.084 mm(0.0017 to 0.0033")0.06 to 0.21 mm0.0024 to 0.0083")0.229 to 0.610 mm(0.0090 to 0.0240")0.483 to 0.965 mm(0.0190 to 0.0380")0.254 to 1.500 mm(0.010 to 0.060")