Jeep Engines - Oljeep

42 MOPAR PERFORMANCE PARTSINTRODUCTIONThe 2.5L engine's connecting rods are made of castnodular iron with a total weight (less the bearings) of 657-665 grams (23.2-23.5 oz.), and a total length(center-to-center) of 155.52-155.62 mm (6.123-6.127").Connecting rod journal diameter is 53.17-53.23 mm(2.0934-2.0955"). Connecting rod journal width is 27.18-27.33 mm (1.070-1.076").For connecting rod removal and installation procedures,refer to Piston and Connecting Rod Assembly, 'Pistons andRings' section of this chapter.Connecting RodThese heavy duty forgings are shot-peened and Magnafluxed.Includes high strength bolts. Can be used as heavyduty stock replacement. For 2.5L and 4.0L engines only.(Sold individually.)P4529209Connecting rod.Connecting Rod BearingsThese connecting rod bearings are made of productionstylematerial. Available in standard and two undersizes.For Jeep 2.5L and 4.0L engines only. (Sold individually.)P4529208Connecting RodsConnecting rod bearings, standard size.P4529236 Connecting rod bearings, .001"undersize.P4529238 Connecting rod bearings, ,010"undersize.Basic Preparation1.2.3.4.5.6.Rods should be checked for alignment; bores should beparallel. Check big and small ends for size. Use only aSunnen rod reconditioner for this purpose.Using a small file, deburr rods, paying particularattention to the mating surfaces and the tab groove.You need the clamping effect of a 60 micro bore. Thesides should be polished by hand on a flat plate using#600 paper.In an engine that is to used in a high rpm situation, therods and rod bolts should be Magna-Glo checked forcracks or forging flaws.A race engine should use the heavy duty rod bolts and nuts.The rod bearing clearances should be 0.03-0.06 mm(0.001 -0.0025").The rod bolt head should be seated against the flat,machined surface in the rod.7. For a race engine, the big end rod should be sized tothe minimum diameter to get the maximum crush fromthe bearing.8.9.Shot-peening the rods is recommended if they haven'tbeen already.Clean all parts before proceeding.Rod RatioFor all-out modified race engines, it is recommended that arod ratio (length of the rod divided by the stroke) of 1.75 to1.85 be maintained (if possible) for best performance. (Thestock 2.5L engine has a rod ratio of I .92 - this is consideredlong.) Side clearance should be 0.25-0.48 mm (0.010-0.019").Inspection1. Connecting Rod BearingsInspect connecting rod bearings for scoring and bentalignment tabs (Figure 2-29 and Figure 2-30). Checkthe bearings for normal wear patterns, scoring,grooving, fatigue and pitting (Figure 2-3 1). Replaceany bearing that shows abnormal wear.Inspect connecting rod journals for signs of scoring,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 indicates the probability of a misalignedconnecting rod, inspect it for correct rod alignment.Replace misaligned, bent or twisted connecting rods.WALONI LO~ER J8909- 27LFigure 2 - 29.~..- .T-l