Jeep Engines - Oljeep

4.0L POWER TECH IN-LINE 6 (CYLINDER HEAD) 175In aluminum heads, the seats and guides are always inserts.The insert (seat or guide) must be “pressed” into thematerial of the cylinder head. The amount of “press” iscalled the interference fit because the insert itself is actuallylarger than the machined hole into which it goes. Theamount of press is measured in thousandths of an inch(.001”). On a given part it may be ,002’’ or .003”. The trickcomes when you remove a seat or guide. You cannot put inthe same size that you just took out. You must use anoversize seat or guide. The inside diameter can be the samesize if desired, but the outside diameter has to be larger.When you remove a seat or guide, the hole left is slightlylarger than before and it may not be perfectly roundanymore. The same size seat or guide installed in this largerhole will have less press than before, or perhaps no press atall. This means the seat or guide can “fall out” or break (asit falls out). It would be bad for the head in either case!This situation is somewhat like honing the block. When were-hone it, the bores will actually become larger(oversized). Therefore, once you remove a seat or guide,you MUST install an oversize part as the replacement. Ifthe head has been repaired or modified already, then youmust move up to the next size oversize. Each oversize partrequires that the head be machined (sized) properly prior toinstallation. At this point, the head is only as good as themachine shop that did the work.Cleaning and InspectionReplace the cover if it is cracked or damaged in any way. Ifthe pre-cured RTV seal is damaged, replace the cover.If a replacement cover is installed, transfer the PCV valvegrommet and oil filler cap from the original cover to thereplacement cover.Remove any original sealer from the cover sealing surfaceof the cylinder head and clean the surface using a fabriccleaner. Remove all residue from the sealing surface usinga clean, dry cloth.Installation1. Clean the cover and cylinder head sealing surfaceusing a clean dry cloth.2. Install the cover and retaining bolts. Tighten theretaining bolts to specification.3.4.Install the cruise control servo (if removed).Install the PCV molded hoses to the cylinder head cover.CRUISECONTROL.SERVOCYLINDER HEAD COVERCrankcase BreatherA universal high performance re-usable crankcase breather(must have stand pipe on valve cover). Washes clean withP4.529392 cleaning fluid for extra miles of service.P4529394Crankcase breather.CYLINDERHEADCOVERRemoval1. Remove PCV molded hoses from the cover (Figure 4-22).2. Remove the cruise control servo, if equipped(Figure 4-22).3.Remove cylinder head cover retaining bolts.14.Lift and remove the cover. The cylinder head coverutilizes a pre-cured RTV sealer that is attached to thecover. Inspect the sealer for cracks and/or damage thatmay have occurred during removal.HOSE-1805. Small cracks in the sealer are allowed and can berepaired by applying RTV sealer to the cracked areabefore cylinder head cover installation.Figure 4 - 22