Jeep Engines - Oljeep

146 MOPAR PERFORMANCE PARTSCurrently, the NHRA requires an SFI approved vibrationdamper as mandatory equipment in Comp Eliminator,Super Stock, Super Comp, Super Gas, and Super Street.They are also permitted in Stock Eliminators. Since January1991, these SFI dampers have been mandatory on all E.T.bracket vehicles that run 10.99 and quicker. If you run a fastvehicle, you should be aware of these special dampers.There are basically three vibration damper approaches thatcan be used. You can use a solid hub damper, afluidviscous damper, or a rubber-style damper. DO NOTUSE A SOLID HUB DAMPER. It breaks crankshafts. Thisleaves the comparison between rubber and viscousdampers. Realize that production (stock) dampers work finein stock condition, but they are not legal in fast vehicles;i.e., they are not SFI approved. Now the question becomeswhich one to use?The first consideration is cost. Rubber dampers tend to beless expensive. However, this is like selecting a cast ironintake manifold over an aluminum one because the cast ironmanifold costs less. There’s more to it than that.The second consideration is inertia. This translates into adamper’s rotational weight. Without getting into fancyterms with a rubber damper, everything has to rotate withthe crankshaft and at the same speed (rpm) as thecrankshaft. This isn’t true of a fluidhiscous damper. Alarge part of the viscous damper’s weight doesn’t follow theengine’s rpm exactly. It works something like a viscous fan.This can be a big advantage in a drag engine or short trackengine where engine speeds change quickly and by largeamounts.One of the characteristics of a rubber damper is that it hasto be tuned to a selected rpm band of operation. This meansthat, for any given engine package, the damper is tuned toa specific rpm. The viscous damper does a better job at awide range of frequencies (rpms). This again is a bigadvantage for the racer who races under many differentconditions, rpms, track lengths, etc.The only real “problem” with rubber dampers is that therubber can deteriorate. This can manifest itself in the outerring slipping. This causes the timing mark to move. At thispoint the damper should be replaced.In summary, we recommend that a steel ring (SFIapproved) vibration damper be used for general highperformance (dual purpose) vehicles, and a viscous/fluidvibration damper be used for race-only drag, oval track, orendurance vehicles.Damper Attachment PackageAttaching bolt package necessary to attach damper tocrankshaft.P4529677 Damper attachment package.Vibration Damper FailureBasically, vibration dampers keep the crankshaft frombreaking. Longer stroke crankshafts work the vibrationdamper harder. So do higher rpm and more output to alesser degree. Lighter dampers don’t do as good a job asheavy dampers. Racing engines today are getting largerwith longer strokes. We need the best damper we can get tokeep the crankshaft from breaking. Without extensivetesting, the best rule is the heavier the better. Theproduction weight damper is another good guideline sincethere has been more testing on it than any other.Most crankshaft failures are the result, not the cause. Thedamper causes the crankshaft to fail, not the other wayaround. If a crankshaft fails, always look to oiling first, thenthe damper. You can’t blame an oiling failure on thedamper. But you also have to select the damper that allowsthe crankshaft to work. If you take weight out of the damperand the crankshaft fails, you know you went too far!Vibration Damper Performance TipsWe have covered the advantages of a good race vibrationdamper. Like any race piece, there are always littleproblems that crop up as you get into actual racing, such asnotching pistons for a big camshaft and matching ports onthe intake manifold. Vibration dampers are no exception.First of all, always double check the timing mark. Doublecheck it against actual top dead center (TDC). This tipreally has nothing to do with the damper itself. We(DaimlerChrysler) have told racers over and over again tocheck the timing marks on their dampers. Check, check,and recheck! You should never switch dampers withoutchecking the timing mark. Remark your damper asrequired. (Refer to Top Dead Center (TDC), in this section,for complete information.)Another tip concerns pulley spacing. Proper spacing hasbeen a problem on every high rpm engine built. Aluminumpul!eys add to the complexity of the problem. There is noeasy solution. Aligning the various pulleys so that all thebelts run true takes a little bit of patience and somemeasuring, but it must be done.Removal1, Remove the drive belt(s).2. Remove the retaining bolts and separate the vibrationdamper pulley (V-belt ONLY) from the vibration damper.3.4.Remove the vibration damper retaining bolt and washer.Use a vibration damper removal tool to remove thedamper from the crankshaft (Figure 2-2).