Jeep Engines - Oljeep

4.0L POWER TECH IN-LINE 6 (CAMSHAFT AND VALVE GEAR) 177CAMSHAFT SELECTIONThere are literally thousands of camshaft designs to choosefrom. Picking the correct one for you and your enginewithout spending too much money is a very tough job.Selecting the type of camshaft (hydraulic, mechanical,roller) is usually the hardest job.Keep in mind that these basic decisions should be made beforeyou go to the track, while you're building the engine. Oncebuilt, the engine will dictate many of the cam's characteristics.Thls choice does affect the valve-to-piston clearance.The easiest way to identify the type of camshaft is bylift-each category has a lift range in which it works best.LlFT TYPE COMMENTS0-,520'' Hydraulic Low maintenance,inexpensive,simplest installation and setup..490-.620" Mechanical Higher rpm, simple..620-.700" Mechanical- High output without roller'sMushroom expense..600-.750" Roller Ultimate power, mostexpensive, most complicated,highest maintenance.The preceding chart can be used to generalize your camshaftselection, although there is some overlap as well as somespecial considerations. It is very general. Your choice maybe already made for you by your local race sanctioning body(check the rule book). Roller and mushroom camshafts arecommonly ruled "out," and sometimes camshafts are limitedto any hydraulic or any flat-tappet.Racing Camshaft SelectionIn mid-race season, many racers are looking to upgradetheir engine's performance. The camshaft is one part that isoften changed. The question is, what direction to go? Toanswer this, we have to back up to how we made ouroriginal or existing choice. To this end, let's review somegeneral selections.A camshaft can be selected by knowing the performancelevel desired for the vehicle and track-type. This is the bestway to select a camshaft, but we have to know how fast thevehicle is going to go. As we're building the engine andselecting our initial camshaft, this performance estimate issomewhat of a guess. Once we've run the engine at thetrack, we can improve upon this guess.Camshafts can be selected based on many different aspects.The best sources of information for selecting camshafts areas follows, listed in order of importance:Dyno curve-in vehicle testThis book0 Camshaft liftOverlapAdvertised durationDuration at fiftyWe hope you will read this entire book to gain as muchknowledge as you can. But say you need more informationto narrow your choice. Now what do you do? Camshaftspecifications can be used to indicate some engineperformance characteristics and potential. Although not asgood or reliable as actual tests, camshaft specifications canindicate trends in an engine's performance. Let's look at thevarious specifications in order of importance.1. LiftHas a direct effect on power, especially under .600".More lift, more power (less torque).2. OverlapAffects idle quality and driveability.3. DurationNot too useful in general. For lifts under .600", theadvertised duration can be useful as long as all thecamshafts being considered are from the samemanufacturer. If more than one manufacturer isinvolved, go back to lift. Duration at fifty (.OSO") isuseful in hard core, all-out race camshafts andcamshafts with lifts over .600".Studying this list closely you'll notice that, of all the camshaftspecifications available, lift is the one to use if test results orMopar Performance Parts recommendations are not available.