Jeep Engines - Oljeep

4.0L POWER TECH IN-LINE 6 (CAMSHAFT AND VALVE GEAR) 1935. Rotate the crankshaft counterclockwise (viewed fromthe front of the engine) 90”.6.7.8.9.Install a dial indicator on the end of the No. 1 cylinderintake valve pushrod. Use rubber tubing to secure theindicator stem on the pushrod.Set the dial indicator pointer at zero.Rotate the crankshaft clockwise (viewed from the frontof the engine) until the dial indicator pointer indicates0.305 mm (0.01 2”) travel distance (lift).The timing notch index on the vibration dampershould be aligned with the TDC mark on the timingdegree scale.If the timing notch is more than 13 mm (1/2”) awayfrom the TDC mark in either direction, the valvetiming is incorrect.If the valve timing is incorrect, the cause may be abroken camshaft pin. It is not necessary to replace thecamshaft because of pin failure. A spring pin isavailable for service replacement.Polished Valve StemsFor many years, we have told racers to polish their valvestems. This recommendation comes originally from Mr.Tom Hoover, generally accepted as the father of the 426Hemi. His quote was, “Like a mirror!” This process is quitesimple and doesn’t take very long. You start with verysmooth sand paper-400 to 800 grit. Then you move up tofiner cloths. Remember, you don’t want to remove anymaterial, you just want to make the stem smooth. You canstart the process by hand, but a drill press or similarmachine is generally used for the final polishing. Careshould be exercised to make sure that the valve is securelychucked in the drill press and at the same time no marks areleft in the valve stem by the drill press chuck jaws. Thisshould be done to every valve prior to installation.For most of us, this is just good engine building procedure.For some of us, it may reduce valve guide wear, increasecylinder head and engine durability, and reduce oilconsumption. In rare cases it even keeps valve guides frombeing destroyed, which would also destroy valve seatsresulting in a very expensive head repair or replacement.Valve Stem Lash CapsMopar Performance Parts valve stem lash caps have thefollowing features:Hardened steel for improved rocker tip durabilityFit between the end of the valve and the rocker arm tipLarger area than stock valve tip to help spread therocker loadsSold in sets of 16 pieces~-Valve Stem Lash CapsP4 120626P4 120635P45 29 83 9VALVE STEM OIL SEALSValve stem lash caps, 3/8“ stem.Valve stem lash caps, 5/16” stem.Valve stem lash caps, 11/32” stem.Most expensive, professional race car engines don’t usevalve stem oil seals because they are rebuilt after everyrace. For the rest nf us, valve stem oil seals are veryimportant. The 4.0L engine standard production valve stemoil seals are made of rubber and incorporate a garter springto maintain consistent lubrication control.Valve stem oil seals control oil flow down the valve stem.If they fail to do their job, oil will get into the combustionchamber. This will cause your oil consumption to go up. Oilis poor fuel, so burning it in the combustion chamber willlower the amount of heat made in the combustion cycle andtherefore lower the amount of power made. Oil is also apoor fuel in that it lowers the overall octane of the fuelmixture in the combustion chamber and can causedetonation problems. Detonation problems can lead tospark plug fouling, which may be misinterpreted as anignition problem.For anyone but the “pros,” a valve seal should be used. Thequestion is, which one? The keys to answering this questionare the valve spring and the camshaft.The best valve seal is the Mopar Performance Parts Vitonseal (P4529240). It is called an “umbrella” seal. It is madeof a special high temperature Viton rubber and slips overthe valve stem. The “umbrella” drops over the top of thevalve guide. This requires the inside diameter of the seal tobe larger than the outside diameter of the valve guide. Inthis manner, the seal shrouds the valve stem from the oil.However, the larger outside diameter of the seal means thatit can’t be used with dual valve springs.If you use dual valve springs, you have to use a PerfectCircle race seal. It attaches to the top of the valve guideitself. Therefore, the guide may have to be sized to get theseal to fit properly. Unlike the umbrella seal which movesup and down with the valve, the Perfect Circle race sealdoesn’t move. The valve stem slides by and the seal “wipesoff’ the oil. Since umbrella seal\ have no relativemovement to the valve stem, they are used in productionengines for maximum mileage/durability. The PerfectCircle seal is not used in production engines but isrecommended with dual springs.Valve stem size is the major determining factor whenselecting valve stem seals. All standard production 4.0Lvalves (including oversize) are 8 mm stem. For a singlespring with damper, use heavy duty Viton seals(P4529240). They work well for camshafts up to .5 10” lift.