Jeep Engines - Oljeep

4.0L POWER TECH IN-LINE 6 (CAMSHAFT AND VALVE GEAR) 189Jeep 4.0L Valve Specifications ChartPart Number Location Diameter Length Material ModificationP4529212 Intake std. Std. Std. Std. Back-cut, 8 mmP45292 13 Exhaust Std. Std. Std. Back-cut, 8 mmP5249875 Intake 1.92" 4.91" Stainless 8 mm stemP5249877 Intake 1.97" 4.9 1 " Stainless 8 mm stem-P.5249879 Exhaust 1.50" 4.93" Stainless 8 mm stemP5249880 Exhaust 1 S6" 4.93" Stainless 8 mm stemLength changes the installed spring height and rocker armgeometry. Stem size affects the guide. A smaller stem valvecan be installed in wedge heads by installing the proper sizevalve guides. Smaller stem valves are lighter. Less valveweight increases the engine speed with a given valve spring,but weaker valves break in expensive failures. Therefore,lightweight valves are made of stainless steel or titaniummaterial. Lock groove changes require new keepers.INTAKEVALVEFEXHAUSTVALVEThat leaves valve head diameter and profile. Valve headdiameter is selected by the performance desired as it isrelated to the other parts used. There are two basic valvehead profiles: tulip and nail-head. See Figure 4-26. Actualproduction valves are halfway in between.Wedge heads perform better with nail head valves. Theyalso perform better if the valve seat is high in the headmaking the valve sit high. Sinking wedge valves hurtsperformance. The valve job should be done with only theminimum amount of material removed. One of the bigperformance advantages to oversize valves is that the seatcan be brought up after it has been sunk by repeated valvejobs with the smaller valve. The valve tips should not beground to shorten them or to even them up because the tiphardness is removed. If they are ground or cut, the tipshould be rehardened or the valve tip will wear poorly andmushroom over.In high output race engines we highly recommend installingbronzewall valve guides. If the head to be raced is a usedpiece, bronzewall guides are almost mandatory. Once thebronzewall guides have been installed, the valves and seatscan be ground more accurately and held to closer tolerances(narrower seats, etc.) without sacrificing durability.VALVE SPRINGRETAINER LOCKGROOVESn. Figure 4 - 25Pwo6INail HeadFigure 4 - 26T -- -1 n