Jeep Engines - Oljeep

4.0L POWER TECH IN-LINE 6 (ENGINE ASSEMBLY) 2597. For better race engine oiling with a high capacity oilpump, 360” main bearing oiling is desired. 360” fullygrooved main bearing sets should be used. It is NOTrecommended that the crankshaft itself be groovedbecause grooves weaken the crankshaft.8.A degreed damper is a must for racers since they mustset their timing by total degrees advanced at a fairlyhigh rpm (for example, 35” total at 2,500 rpm). Adegreed damper is the easiest, most accurate, and mostconvenient tool for doing this. It also aids in setting thevalve lash by giving 90” reference marks.Note: Damper degree timing tape is P4529070.Measuring Main Bearing and Connecting RodBearing Clearances(Refer to ‘Crankshaft’ and ‘Connecting Rods’ sections ofthis chapter for detailed instructions.)Cylinder Head1.2.3.4.5.6.7.8.The cylinder head should be “cc’d’ and the volumescompared to specifications. Any milling that isrequired should be done, and the chamber volumesrechecked.The cylinder head should be checked for squarenessand for any cracks or flaws. The valve guides shouldalso be checked for wear and replaced if necessary.The cylinder head should have a valve job done if theseat runout does not meet specifications: 0.064 mm(0.0025”). Refer to ‘Camshaft and Valve Gear’ and‘Cylinder Head’ sections of this chapter for moreinformation.The cylinder head should be installed on the blockwithout the head gasket to check dowel pin height.Dowel pins should NOT hold the cylinder head up offthe block surface; they should only locate it over thecylinder bores.When high lift camshafts are installed in productionbasedengines, the keepers may hit the valve guide. Thisshould be checked at the cam’s maximum lift. The guideshould be shortened to give .100“ clearance between thetop of the guide and the bottom of the keepers.When dual valve springs are used, the inner spring seatmay have to be cut down flush with the outer spring seat.With the crankshaft, pistons, and connecting rodsremoved, check the alignment of the combustionchamber over the cylinder bore. If it needs to becorrected, use offset dowel pins in the block.The latest tech trend in Stock and Super Stock racing isto “cc” the ports-both intake and exhaust. This isn’t atechnique to increase performance; rather, it’s ameasurement technique used by the NHRA and IHRAat the tech barn. They have a cc number for the portvolume and your cylinder head will be checked againstthat number. Refer to the ‘Cylinder Head’ section ofthis chapter for complete information.Connecting RodsNote: The following information is for the preparation ofsteel connecting rods only.I. Connecting rods should be checked for alignment; boresshould be parallel. Check big and small ends for size.2. Using a small file, deburr the connecting rods, payingparticular attention to the mating surfaces and tabgroove. You need the clamping effect of a 60 microbore. The sides should be polished by hand on a flatplate using #600 paper. Proper side clearance should be0.25-0.48 mm (0.010-0.019”). DO NOT increase sideclearance past .019” as this increases the oil demand ofthe engine. It will also allow too much oil on thecylinder walls which will overload the rings and allowexcess oil in the combustion chambers.3.In an engine that is to be used in a high rpm situation,the connecting rods and connecting rod bolts should beMagna-Glo checked for cracks or forging flaws.4. A race engine should always use heavy dutyconnecting rod bolts and nuts.5.6.7.8.9.The connecting rod bearing clearance is 0.25-0.76 mm(0.001-0.003”). Preferred bearing clearance is 0.044-0.050 mm (0.0015-0.0020”).The connecting rod bolt head should be seated againstthe flat, machined surface in the connecting rod.For a race engine, the big end of the connecting rodshould be sized to the minimum diameter to get themaximum crush from the bearing.Shot-peening the rods is recommended if they haven’tbeen already.Some race engines use floating piston pins. On theseengines, the pin-to-connecting rod clearance shouldbe checked. On standard production engines that usea pressed pin, the amount of interference should bechecked. (Refer to 4.0L Engine Specifications, inthis section.)10. Connecting rods with full floating pins to be used inracing applications should have the small end of theconnecting rod drilled with a small hole(approximately 3/32”) for increased piston pin oiling.The best location for this oiling hole is the top of theconnecting rod above the pin (Figure 4-11). Pin oilingholes in the sides (5 o’clock or 7 o’clock, for example)weaken the connecting rod itself and therefore areNOT recommended. One hole in the top does the bestjob of oiling the pin and maintaining the connectingrod’s strength...- ‘IT1-