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====== EVO: Engine Mechanicals - Sub-04S ======
====== Top End Oiling ======

====== Rocker Box Oiling ======
==== 1991-1999 engines ====

    * Crankcase pressure (air and oil mist) is routed up the pushrod tubes (bypassing the falling oil from the rocker boxes) into the rocker box.
    * Collected air pressure and oil mist in each rocker box is routed up into a sealed cavity in the lower portion of the box.
    * This mixture passes up from underneath a rubber one-way valve (umbrella valve) sitting over the cavity inlet.
    * The oil is designed to separate from the air by;
      * Hitting the underside of the umbrella valve and falling back into the sealed cavity in the middle rocker box.
      * From there it should drain back into the lower rocker box through a tiny hole behind the umbrella valve.
      * This tiny hole is in a recessed area behind the umbrella valve.
      * There is a certain amount of backpressure in the sealed cavity away from the air exit hole.
      * This backpressure should help push the oil into the tiny hole and back into the lower rocker box area to be carried back down to the lower end.
      * The upstroke of the pistons causes a vacuum to form in the system. \\ This vacuum is also pulled through the oil passage from the heads / rocker box. \\ (in theory, it should help pull oil through the drains in the heads to the bottom end.
  * Air pressure is designed to continue up past the umbrella valve and exit a hole in each head on the intake valve side.
  * Pressure escapes the head through the hollow bolts (one in each head) that hold the air cleaner mount.

==== 2000 and Up engines ====

===== Rocker Arm / Valve Oiling =====
==== All ====

      * Oil flows up the holes in the pushrods from the lifters and enters the rocker arms through a hole in the pushrod end of the arm.
      * Oil is supplied to each valve stem and springs from the drilled holes in the underside of each rocker arm above them.
        * The holes are only on the valve side of each rocker arm. 
      * Oil is also forced through the clearance between the rocker arm shafts and bushings for lubrication there.

|  Valve oiler holes in Rockers ((photo by Hippysmack))  |  Rocker arm oiling path ((photo by Hippysmack))  |
|{{:techtalk:evo:oil:rocker_arm-valve_oiler_holes_by_hippysmack.jpg?direct&300|}}|{{:techtalk:evo:oil:rocker_arm_oil_path-_exhaust_by_hippysmack.jpg?direct&300|}}|

|  Valve Squirter Hole Locations ((photos by Hippysmack))  ||
|{{:techtalk:evo:oil:rocker_arm_-_valve_squirter_locations_pic1_by_hippysmack.jpg?direct&300|}}|{{:techtalk:evo:oil:rocker_arm_-_valve_squirter_locations_pic2_by_hippysmack.jpg?direct&300|}}| 


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