Valve displacement dictates the size by which the valves extend into the cylinder while the time for which the valve remains opened or closed is equally critical. In the case where valve clearance is set too high the following consequences are possible: increased wear of the camshaft and incomplete opening of the valve, the appearance of a tapping sound from the valve mechanism and unsatisfactory work of the engine due to limited gas exchange. Inadequate clearance, on the other hand, results to poor seating of the intake and exhaust valves leading to leakage of gases in the combustion chamber and consequent heating of the valves, and since there is little heat transfer, the valves might end up being warped. Its important that the adjustments be accurate but it is better for the valves to be slightly big rather than small to avoid burning. Since both 2.0L and 2.3L are gasoline engines, they have a hydraulic valve train that requires no periodic adjustments. Some general changes include; 2.2L and 2.3L diesel engines require the following; warm up the engine, take off the valve cover, check head bolts, for torque and then only adjust the selected valves at Top Dead Center. When adjusting the stacks, one removes the lock nuts, rotates the adjusting screw clock wise or anti-clock wise to hit the standard specified clearance and ensures the all the stacks are clean before they are re-fixed on the plates. On the 2.4L engine, it is done on cold engine that calls for disconnecting the battery, withdrawing the rocker arm cover, and adjusting the intake and exhaust valves to correct clearance using the feeler gauges. 2.9L usually does not need adjustments and when it does the process it entails positioning of your cams, removal of screws and very delicate adjustment until you get the right plunger position. Moreover, the above 4.0L engine incorporates a hydraulic roller valvetrain, which does not require adjustment after some times.
